WO2023144653A1 - Storage device - Google Patents

Abstract

Provided is a novel storage device. Provided is a storage device in which N layers (N is an integer of 2 or more) of a storage layer are stacked, the storage layer including a plurality of memory cells disposed in a matrix shape. A bit line and a selection line are disposed along a stacking direction of the storage layers, and a write word line and a read word line are disposed in a direction orthogonal to the stacking direction of the storage layers. The memory cells have a first transistor, a second transistor, and a capacitative element. Either the source or the drain of the first transistor is electrically connected to the bit line via a first conductor having a region that functions as either a source electrode or a drain electrode. At least one of an upper surface, a lateral surface, and a lower surface of the first conductor has a region that is in contact with the bit line.

Description

Storage device

One aspect of the present invention relates to a storage device.

Note that one embodiment of the present invention is not limited to the above technical field. The technical field of the invention disclosed in this specification and the like relates to products, methods, or manufacturing methods. Alternatively, one aspect of the invention relates to a process, machine, manufacture, or composition of matter.

Therefore, examples of the technical field according to one embodiment of the present invention include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, power storage devices, imaging devices, storage devices, signal processing devices, processors, electronic devices, systems, and the like. Driving methods, methods of manufacturing them, methods of inspecting them, methods of using them, and the like can be mentioned.

In recent years, semiconductor devices such as LSIs, CPUs, and memories (storage devices) have been developed. These semiconductor devices are used in various electronic devices such as computers and personal digital assistants. In addition, memories of various storage methods have been developed according to uses, such as temporary storage during execution of arithmetic processing and long-term storage of data. Typical memory systems include DRAM, SRAM, and flash memory.

In addition, as the amount of data to be handled increases, a semiconductor device having a larger storage capacity is required. Patent Document 1 and Non-Patent Document 1 disclose a memory cell formed by stacking transistors.

WO2021/053473

An object of one embodiment of the present invention is to provide a storage device with a large storage capacity. Another object is to provide a memory device that occupies a small area. Another object is to provide a highly reliable storage device. Another object is to provide a memory device with low power consumption. Another object is to provide a novel storage device.

Note that the problem of one embodiment of the present invention is not limited to the problems listed above. The issues listed above do not preclude the existence of other issues. Note that other problems are problems that are not mentioned in this item and will be described in the following description. Problems not mentioned in this section can be derived from descriptions in the specification, drawings, or the like by a person skilled in the art, and can be appropriately extracted from these descriptions. Note that the problems related to one aspect of the present invention do not necessarily solve all of the above-listed problems and other problems. One aspect of the present invention is to solve at least one of the problems listed above and other problems.

One embodiment of the present invention includes N memory layers (N is an integer of 2 or more), a plurality of first wirings extending in a first direction that is a stacking direction of the N memory layers, and a plurality of second wirings extending, a plurality of third wirings extending in a second direction perpendicular to the first direction, and a plurality of fourth wirings extending in the second direction; each of the memory layers has a plurality of memory cells arranged in a matrix, each of the plurality of memory cells has a first transistor, a second transistor, and a capacitive element; is electrically connected to one of the plurality of third wirings, one of the source or the drain of the first transistor is electrically connected to the first wiring through the first conductor, and one of the capacitive elements is electrically connected to the fourth wiring, one electrode of the capacitor is electrically connected to the other of the source or the drain of the first transistor and the gate of the second transistor, and the source of the second transistor Alternatively, one of the drains is electrically connected to the first wiring, the other of the source or the drain of the second transistor is electrically connected to the second wiring, and the first conductor has the top surface, the side surface, and the bottom surface. At least one is a memory device having a region in contact with the first wiring.

One of the source and the drain of the second transistor may be electrically connected to the first wiring through the second conductor. It is preferable that at least one of the top surface, the side surface, and the bottom surface of the second conductor has a region in contact with the second wiring.

The other of the source and the drain of the second transistor may be electrically connected to the second wiring through the third conductor. It is preferable that at least one of the top surface, the side surface, and the bottom surface of the third conductor has a region in contact with the second wiring.

Preferably, the first transistor is a transistor with a back gate. The first transistor is preferably a transistor including an oxide semiconductor.

According to one embodiment of the present invention, a storage device with a large storage capacity can be provided. Alternatively, a memory device occupying a small area can be provided. Alternatively, a highly reliable storage device can be provided. Alternatively, a storage device with low power consumption can be provided. Alternatively, a new storage device can be provided.

Note that the effects of one embodiment of the present invention are not limited to the effects listed above. The effects listed above do not preclude the existence of other effects. Accordingly, one aspect of the present invention may not have the effects listed above. Note that other effects are effects that are described in the following description and are not mentioned in this item. Other effects can be derived from descriptions in the specification, drawings, etc. by those skilled in the art, and can be appropriately extracted from these descriptions. One aspect of the present invention has at least one of the effects listed above and other effects.

FIG. 1A is a perspective view illustrating a configuration example of a semiconductor device. FIG. 1B is a block diagram illustrating a configuration example of a semiconductor device.
FIG. 2A is an enlarged perspective block diagram of a portion of the storage layer. FIG. 2B is a plan view of part of the storage layer as seen from the Z direction.
FIG. 3A is a schematic cross-sectional view of a memory cell. FIG. 3B is a circuit configuration example of a memory cell.
FIG. 4 is a diagram showing a cross-sectional configuration example of a memory layer.
FIG. 5 is a diagram showing a circuit configuration example of a memory layer.
FIG. 6 is a timing chart for explaining an operation example of the memory cell 10. FIG.
7A and 7B are circuit diagrams for explaining an operation example of the memory cell 10. FIG.
8A and 8B are circuit diagrams for explaining an operation example of the memory cell 10. FIG.
9A to 9D are diagrams illustrating configuration examples of a semiconductor device.
FIG. 10 is a diagram illustrating a configuration example of a semiconductor device.
11A to 11C are diagrams illustrating configuration examples of a semiconductor device.
12A and 12B are diagrams for explaining a configuration example of a semiconductor device.
13A and 13B are diagrams for explaining a configuration example of a semiconductor device.
14A to 14D are diagrams illustrating configuration examples of semiconductor devices.
FIG. 15 is a diagram illustrating a configuration example of a semiconductor device.
16A and 16B are perspective views showing an example of electronic components.
17A to 17J are diagrams illustrating examples of electronic devices.
18A to 18E are diagrams illustrating examples of electronic devices.
19A to 19C are diagrams illustrating examples of electronic devices.

Hereinafter, embodiments described in this specification will be described with reference to the drawings. Those skilled in the art will readily appreciate, however, that the embodiments can be embodied in many different forms and that various changes in form and detail can be made without departing from the spirit and scope thereof. be. Therefore, the present invention should not be construed as being limited to the description of the embodiments. In addition, in the configuration of the invention of the embodiment, the same reference numerals may be used in common for the same parts or parts having similar functions in different drawings, and repeated description thereof may be omitted. Moreover, when referring to similar functions, the hatch patterns may be the same and no particular reference numerals may be attached. Also, in order to facilitate understanding of the drawings, description of some components may be omitted in perspective views, top views, and the like.

In addition, in the drawings and the like of this specification and the like, sizes, layer thicknesses, and regions may be exaggerated for clarity. Therefore, it is not necessarily limited to its size or aspect ratio. The drawings schematically show ideal examples, and are not limited to the shapes or values shown in the drawings. For example, variations in signal, voltage, or current due to noise or variations in signal, voltage, or current due to timing shift can be included.

In this specification and the like, a semiconductor device is a device that utilizes semiconductor characteristics and refers to a circuit including a semiconductor element (transistor, diode, photodiode, or the like), a device having the same circuit, and the like. It also refers to all devices that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip with an integrated circuit, and an electronic component in which the chip is housed in a package are examples of semiconductor devices. In addition, storage devices, display devices, light-emitting devices, lighting devices, electronic devices, and the like are themselves semiconductor devices and may include semiconductor devices.

In addition, in this specification and the like, when it is described that X and Y are connected, it means that X and Y are electrically connected and that X and Y are functionally connected. This specification and the like disclose a case where X and Y are directly connected and a case where X and Y are directly connected. Therefore, it is assumed that the connection relationships other than the connection relationships shown in the drawings or the text are not limited to the predetermined connection relationships, for example, the connection relationships shown in the drawings or the text. It is assumed that X and Y are objects (for example, devices, elements, circuits, wiring, electrodes, terminals, conductive films, layers, etc.).

An example of the case where X and Y are electrically connected is an element that enables electrical connection between X and Y (for example, switch, transistor, capacitive element, inductor, resistive element, diode, display devices, light emitting devices, loads, etc.) can be connected between X and Y.

As an example of the case where X and Y are functionally connected, a circuit that enables functional connection between X and Y (eg, a logic circuit (inverter, NAND circuit, NOR circuit, etc.), a signal conversion Circuits (digital-to-analog conversion circuits, analog-to-digital conversion circuits, gamma correction circuits, etc.), potential level conversion circuits (power supply circuits (booster circuits, step-down circuits, etc.), level shifter circuits that change the potential level of signals, etc.), voltage sources, current sources , switching circuit, amplifier circuit (circuit that can increase signal amplitude or current amount, operational amplifier, differential amplifier circuit, source follower circuit, buffer circuit, etc.), signal generation circuit, memory circuit, control circuit, etc.) It is possible to connect one or more between As an example, even if another circuit is interposed between X and Y, when a signal output from X is transmitted to Y, X and Y are considered to be functionally connected. do.

It should be noted that when explicitly describing that X and Y are electrically connected, it means that X and Y are electrically connected (that is, another element or another circuit is interposed), and the case where X and Y are directly connected (that is, the case where X and Y are connected without another element or another circuit between them). (if any).

Also, for example, "X and Y, the source (or the first terminal, etc.) and the drain (or the second terminal, etc.) of the transistor are electrically connected to each other, and X, the source of the transistor (or the 1 terminal, etc.), the drain of the transistor (or the second terminal, etc.), and are electrically connected in the order of Y.". Or, "the source (or first terminal, etc.) of the transistor is electrically connected to X, the drain (or second terminal, etc.) of the transistor is electrically connected to Y, and X is the source of the transistor ( or the first terminal, etc.), the drain of the transistor (or the second terminal, etc.), and Y are electrically connected in this order. Or, "X is electrically connected to Y through the source (or first terminal, etc.) and drain (or second terminal, etc.) of the transistor, and X is the source (or first terminal, etc.) of the transistor; terminal, etc.), the drain of the transistor (or the second terminal, etc.), and Y are provided in this connection order. Using expressions similar to these examples, the source (or the first terminal, etc.) and the drain (or the second terminal, etc.) of the transistor can be distinguished by defining the order of connection in the circuit configuration. Alternatively, the technical scope can be determined. In addition, these expression methods are examples, and are not limited to these expression methods. Here, X and Y are objects (for example, devices, elements, circuits, wiring, electrodes, terminals, conductive films, layers, etc.).

Even if the circuit diagram shows independent components electrically connected to each other, if one component has the functions of multiple components There is also For example, when a part of the wiring also functions as an electrode, one conductive film has both the function of the wiring and the function of the electrode. Therefore, the term "electrically connected" in this specification includes cases where one conductive film functions as a plurality of constituent elements.

In this specification and the like, the term “capacitance element” refers to, for example, a circuit element having a capacitance value higher than 0 F, a wiring region having a capacitance value higher than 0 F, a parasitic capacitance, a transistor can be the gate capacitance of Therefore, in this specification and the like, the term “capacitance element” means not only a circuit element including a pair of electrodes and a dielectric material contained between the electrodes, but also a parasitic element occurring between wirings. Capacitance, gate capacitance generated between one of the source or drain of the transistor and the gate, and the like are included. In addition, terms such as "capacitance element", "parasitic capacitance", and "gate capacitance" can be replaced with terms such as "capacitance", and conversely, the term "capacitance" can be replaced by terms such as "capacitance element", "parasitic capacitance", and "capacitance". term such as "gate capacitance". In addition, the term "a pair of electrodes" in the "capacitance" can be replaced with a "pair of conductors," a "pair of conductive regions," a "pair of regions," and the like. Note that the value of the capacitance can be, for example, 0.05 fF or more and 10 pF or less. Also, for example, it may be 1 pF or more and 10 μF or less.

In this specification and the like, a transistor has three terminals called a gate, a source, and a drain. The gate is the control terminal that controls the amount of current that flows between the source and drain. The two terminals functioning as source or drain are the input and output terminals of the transistor. One of the two input/output terminals functions as a source and the other as a drain depending on the conductivity type of the transistor (n-channel type, p-channel type) and the level of potentials applied to the three terminals of the transistor. Therefore, in this specification and the like, the terms "source" and "drain" can be used interchangeably.

Note that in this specification and the like, a gate means part or all of a gate electrode and a gate wiring. A gate wiring is a wiring for electrically connecting a gate electrode of at least one transistor and another electrode or another wiring. For example, a scanning line in a display device is also included in the gate wiring.

A source refers to part or all of a source region, a source electrode, and a source wiring. A source region is a region of a semiconductor layer whose resistivity is equal to or less than a certain value. A source electrode refers to a conductive layer that includes a portion connected to a source region. A source wiring is a wiring for electrically connecting a source electrode of at least one transistor and another electrode or another wiring. For example, a signal line in a display device is electrically connected to a source electrode. When the source wiring is used, the signal line is also included in the source wiring.

The drain refers to part or all of the drain region, drain electrode, and drain wiring. The drain region means a region of the semiconductor layer whose resistivity is equal to or less than a certain value. A drain electrode refers to a conductive layer including a portion connected to a drain region. A drain wiring is a wiring for electrically connecting a drain electrode of at least one transistor and another electrode or another wiring. For example, a signal line in a display device is electrically connected to the drain electrode. The signal line is also included in the drain wiring when the drain wiring is used.

In addition, in this specification and the like, when describing the connection relationship of a transistor, “one of the source or the drain” (or the first electrode or the first terminal) and “the other of the source or the drain” (or the second electrode or the 2nd terminal) may be used. Note that a transistor may have a back gate in addition to the three terminals described above, depending on the structure of the transistor. In this case, in this specification and the like, one of the gate and back gate of the transistor may be referred to as a first gate, and the other of the gate and back gate of the transistor may be referred to as a second gate. Further, the terms "gate" and "backgate" may be used interchangeably for the same transistor. In addition, when a transistor has three or more gates, the respective gates may be referred to as a first gate, a second gate, a third gate, or the like in this specification and the like.

In this specification and the like, a "node" can be replaced with a terminal, a wiring, an electrode, a conductive layer, a conductor, an impurity region, or the like, depending on the circuit configuration, device structure, and the like. Also, terminals, wirings, etc. can be rephrased as "nodes".

In this specification and the like, ordinal numbers such as "first", "second", and "third" are added to avoid confusion of constituent elements. Therefore, the number of components is not limited. Also, the order of the components is not limited. For example, a component referred to as "first" in one embodiment such as this specification is a component referred to as "second" in other embodiments or claims. It is possible. Further, for example, a component referred to as "first" in one of the embodiments in this specification may be omitted in other embodiments or the scope of claims.

In addition, in this specification and the like, terms such as “above”, “below”, “above”, or “below” indicate the positional relationship between constituent elements with reference to the drawings. In order to do so, it is sometimes used for convenience. Moreover, the positional relationship between the constituent elements changes as appropriate according to the direction in which each constituent is drawn. Therefore, it is not limited to the words and phrases explained in the specification, etc., and can be appropriately rephrased according to the situation. For example, the expression "insulator on top of conductor" can be rephrased as "insulator on bottom of conductor" by rotating the orientation of the drawing shown by 180 degrees.

In addition, the terms "above" and "below" do not limit the positional relationship of components to being directly above or directly below and in direct contact with each other. For example, the expression “electrode B on insulating layer A” does not require that electrode B be formed on insulating layer A in direct contact with another configuration between insulating layer A and electrode B. Do not exclude those containing elements.

In this specification and the like, terms such as "overlapping" do not limit the order of stacking of constituent elements. For example, the expression “electrode B overlapping the insulating layer A” is not limited to the state in which the electrode B is formed on the insulating layer A, but the state in which the electrode B is formed under the insulating layer A or A state in which the electrode B is formed on the right (or left) side of the insulating layer A is not excluded.

Moreover, in this specification and the like, the terms “adjacent” and “proximity” do not limit that components are in direct contact with each other. For example, in the expression “electrode B adjacent to insulating layer A”, it is not necessary that insulating layer A and electrode B are formed in direct contact, and another component is provided between insulating layer A and electrode B. Do not exclude what is included.

In this specification and the like, terms such as “film” and “layer” can be interchanged depending on the situation. For example, it may be possible to change the term "conductive layer" to the term "conductive film." Or, for example, it may be possible to change the term "insulating film" to the term "insulating layer". Alternatively, as the case may or may be, the terms "film", "layer", etc. can be omitted and replaced with other terms. For example, it may be possible to change the term "conductive layer" or "conductive film" to the term "conductor." Alternatively, it may be possible to change the term "conductor" to the term "conductive layer" or "conductive film". Or, for example, it may be possible to change the term "insulating layer" or "insulating film" to the term "insulator". Alternatively, it may be possible to change the term "insulator" to the term "insulating layer" or "insulating film".

In this specification and the like, terms such as "electrode", "wiring", and "terminal" are not intended to functionally limit these components. For example, an "electrode" may be used as part of a "wiring" and vice versa. Furthermore, the term "electrode" or "wiring" includes the case where a plurality of "electrodes" or "wiring" are integrally formed. Also, for example, "terminal" may be used as part of "wiring" or "electrode" and vice versa. Furthermore, the term "terminal" includes a case where a plurality of "electrodes", "wirings", "terminals", etc. are integrally formed. So, for example, an "electrode" can be part of a "wiring" or a "terminal", and a "terminal" can be part of a "wiring" or an "electrode", for example. Terms such as "electrode", "wiring", and "terminal" may be replaced with terms such as "region".

In this specification and the like, terms such as “wiring”, “signal line”, and “power line” can be interchanged depending on the case or situation. For example, it may be possible to change the term "wiring" to the term "signal line". Also, for example, it may be possible to change the term "wiring" to a term such as "power supply line". In addition, vice versa, terms such as "signal line" and "power line" may be changed to the term "wiring". It may be possible to change terms such as "power line" to terms such as "signal line". Also, vice versa, terms such as "signal line" may be changed to terms such as "power line". In addition, the term "potential" applied to the wiring may be changed to the term "signal" depending on the circumstances. And vice versa, terms such as "signal" may be changed to the term "potential".

In this specification and the like, a "switch" has a plurality of terminals and has a function of switching (selecting) between conduction and non-conduction between the terminals. For example, a switch is said to be "conducting" or "on" if it has two terminals and the two terminals are conducting. Also, when both terminals are non-conducting, the switch is said to be "non-conducting" or "off". Note that switching to one of the conducting state and the non-conducting state, or maintaining one of the conducting state and the non-conducting state may be referred to as "controlling the conducting state."

In other words, a switch has a function of controlling whether or not to allow current to flow. Alternatively, a switch is one that has a function of selecting and switching a path through which current flows. As an example, an electrical switch, a mechanical switch, or the like can be used. In other words, the switch is not limited to a specific one as long as it can control current.

Examples of switches include transistors (eg, bipolar transistors, MOS transistors, etc.), diodes (eg, PN diodes, PIN diodes, Schottky diodes, MIM (Metal Insulator Metal) diodes, MIS (Metal Insulator Semiconductor) diodes, diode connections transistors), or a logic circuit combining these. Note that when a transistor is used as a switch, the “on state” of the transistor means a state in which the source electrode and the drain electrode of the transistor can be considered to be electrically short-circuited. A “non-conducting state” of a transistor means a state in which a source electrode and a drain electrode of the transistor can be considered to be electrically cut off. Note that the polarity (conductivity type) of the transistor is not particularly limited when the transistor is operated as a simple switch.

One example of a mechanical switch is a switch using MEMS (Micro Electro Mechanical Systems) technology. The switch has an electrode that can be moved mechanically, and selects conduction or non-conduction by moving the electrode.

Note that in this specification and the like, the “on state” (sometimes abbreviated as “on”) of a transistor means a state in which the source and drain of a transistor can be considered to be electrically short-circuited (also referred to as a “conducting state”). say.) Alternatively, unless otherwise specified, in an n-channel transistor, the “on state” means that the voltage between the gate and the source (also referred to as “gate voltage” or “Vg”) is the threshold voltage (“Vth”). The above state is a state in which Vg is equal to or lower than Vth in a p-channel transistor.

An “off state” (sometimes abbreviated as “off”) of a transistor means a state in which the source and drain of the transistor can be considered to be electrically disconnected (also referred to as “non-conducting state”). . Alternatively, the “off state” means a state in which Vg is lower than Vth for an n-channel transistor and a state in which Vg is higher than Vth for a p-channel transistor, unless otherwise specified.

In this specification and the like, the term “on current” sometimes refers to current that flows between the source and the drain when the transistor is on. In addition, "off current" sometimes refers to a current that flows between a source and a drain when a transistor is in an off state.

In this specification and the like, a high power supply potential VDD (hereinafter also simply referred to as “potential VDD” or “VDD”) is a low power supply potential VSS (hereinafter also simply referred to as “potential VSS” or “VSS”). ) indicates a higher potential power supply potential. Further, the low power supply potential VSS indicates a power supply potential lower than the high power supply potential VDD.

Further, when a potential H (hereinafter also simply referred to as “H”) is supplied to the gate of an n-channel transistor, the transistor is turned on. Further, when the potential L (hereinafter also simply referred to as “L”) is supplied to the gate of the n-channel transistor, the transistor is turned off. Therefore, the potential H is a potential higher than the potential L. The potential H and VDD may be the same potential unless otherwise specified. Further, the potential L is a potential lower than the potential H. Unless otherwise specified, the potential L and the potential VSS may be the same potential.

Also, the ground potential can be used as VDD or VSS. For example, when VDD is the ground potential, VSS is a potential lower than the ground potential, and when VSS is the ground potential, VDD is a potential higher than the ground potential.

In this specification and the like, a gate means part or all of a gate electrode and a gate wiring. A gate wiring is a wiring for electrically connecting at least one gate electrode of a transistor to another electrode or another wiring.

In this specification and the like, a source refers to part or all of a source region, a source electrode, and a source wiring. A source region is a region of a semiconductor layer whose resistivity is equal to or less than a certain value. A source electrode refers to a conductive layer that includes a portion connected to a source region. A source wiring is a wiring for electrically connecting at least one source electrode of a transistor to another electrode or another wiring.

In this specification and the like, the term "drain" refers to part or all of a drain region, a drain electrode, and a drain wiring. The drain region means a region of the semiconductor layer whose resistivity is equal to or less than a certain value. A drain electrode refers to a conductive layer including a portion connected to a drain region. A drain wiring is a wiring for electrically connecting at least one drain electrode of a transistor to another electrode or another wiring.

In this specification, "parallel" means a state in which two straight lines are arranged at an angle of -10° or more and 10° or less. Therefore, the case of −5° or more and 5° or less is also included. Moreover, "substantially parallel" or "substantially parallel" refers to a state in which two straight lines are arranged at an angle of -30° or more and 30° or less. "Perpendicular" means that two straight lines are arranged at an angle of 80° or more and 100° or less. Therefore, the case of 85° or more and 95° or less is also included. Moreover, "substantially perpendicular" or "substantially perpendicular" means a state in which two straight lines are arranged at an angle of 60° or more and 120° or less.

In this specification, etc., when referring to count values and measurement values as "same", "same", "equal" or "uniform" (including synonyms), unless otherwise specified , with an error of plus or minus 20%.

In addition, arrows indicating the X direction, the Y direction, and the Z direction may be attached in the drawings and the like according to this specification. In this specification and the like, the “X direction” is the direction along the X axis, and the forward direction and the reverse direction may not be distinguished unless explicitly stated. The same applies to the "Y direction" and the "Z direction". Also, the X direction, the Y direction, and the Z direction are directions that cross each other. More specifically, the X-direction, Y-direction, and Z-direction are directions orthogonal to each other. In this specification and the like, one of the X-direction, Y-direction, and Z-direction may be referred to as "first direction" or "first direction." Also, the other one may be called a "second direction" or a "second direction." In addition, the remaining one may be called "third direction" or "third direction".

In this specification and the like, when the same reference numerals are used for a plurality of elements, especially when it is necessary to distinguish them, the reference characters are "A", "b", "_1", "[n]", "[m , n]”, etc., may be added.

(Embodiment 1)
A configuration example of a memory device 100 including memory cells 10 (also referred to as “storage elements”) will be described.

FIG. 1A shows a schematic perspective view of a configuration example of a storage device 100 that is one embodiment of the present invention. FIG. 1B is a block diagram showing a configuration example of the storage device 100 which is one embodiment of the present invention. The memory device 100 has a drive circuit layer 50 and memory layers 60 of N layers (N is an integer equal to or greater than 1).

The N memory layers 60 are provided on the drive circuit layer 50 . By providing the N memory layers 60 on the drive circuit layer 50, the area occupied by the memory device 100 can be reduced. Also, the storage capacity per unit area can be increased.

In the present embodiment and the like, the first memory layer 60 is indicated as a memory layer 60_1, the second memory layer 60 is indicated as a memory layer 60_2, the third memory layer 60 is indicated as a memory layer 60_3, and the memory layer 60 as a third layer is indicated as a memory layer 60_3. The second storage layer 60 is indicated as a storage layer 60_4. Also, the k-th layer (k is an integer of 1 or more and N or less) is indicated as a memory layer 60_k, and the N-th layer 60 is indicated as a memory layer 60_N. Note that in the present embodiment and the like, when describing matters relating to the entirety of the N storage layers 60, or when indicating matters common to each layer of the N storage layers 60, the term "storage layer 60" is used simply. sometimes.

<Configuration example of drive circuit layer 50>
The drive circuit layer 50 has a PSW 22 (power switch), a PSW 23 and a peripheral circuit 31 . The peripheral circuit 31 has a peripheral circuit 41 , a control circuit 32 (control circuit), and a voltage generation circuit 33 .

In the memory device 100, each circuit, each signal, and each voltage can be appropriately discarded as needed. Alternatively, other circuits or other signals may be added. Signal BW, signal CE, signal GW, signal CLK, signal WAKE, signal ADDR, signal WDA, signal PON1, and signal PON2 are input signals from the outside, and signal RDA is an output signal to the outside. Signal CLK is a clock signal.

Signal BW, signal CE, and signal GW are control signals. Signal CE is a chip enable signal, signal GW is a global write enable signal, and signal BW is a byte write enable signal. Signal ADDR is an address signal. The signal WDA is write data and the signal RDA is read data. A signal PON1 and a signal PON2 are power gating control signals. The signal PON1 and the signal PON2 may be generated by the control circuit 32. FIG.

The control circuit 32 is a logic circuit having a function of controlling the overall operation of the storage device 100 . For example, the control circuit logically operates the signal CE, the signal GW and the signal BW to determine the operation mode (for example, write operation, read operation) of the memory device 100 . Alternatively, control circuit 32 generates a control signal for peripheral circuit 41 so that this operation mode is executed.

The voltage generation circuit 33 has a function of generating a negative voltage. The signal WAKE has a function of controlling the input of the signal CLK to the voltage generation circuit 33 . For example, when an H level signal is applied to signal WAKE, signal CLK is input to voltage generation circuit 33, and voltage generation circuit 33 generates a negative voltage.

The peripheral circuit 41 is a circuit for writing data to and reading data from the memory cell 10 . The peripheral circuit 41 includes a row decoder 42 (Row Decoder), a column decoder 44 (Column Decoder), a row driver 43 (Row Driver), a column driver 45 (Column Driver), an input circuit 47 (Input Circuit), an output circuit 48 ( Output Circuit) and a sense amplifier 46 (Sense Amplifier).

Row decoder 42 and column decoder 44 have the function of decoding signal ADDR. Row decoder 42 is a circuit for specifying a row to be accessed, and column decoder 44 is a circuit for specifying a column to be accessed. The row driver 43 has a function of selecting the wiring WWL (write word line) or the wiring RWL (read word line) specified by the row decoder 42 . The column driver 45 has a function of writing data to the memory cells 10, a function of reading data from the memory cells 10, a function of holding the read data, and the like. The column driver 45 has a function of selecting the wiring BL (write and read bit lines) specified by the column decoder 44 .

Input circuit 47 has a function of holding signal WDA. Data held by the input circuit 47 is output to the column driver 45 . Output data of the input circuit 47 is data (Din) to be written to the memory cell 10 . Data (Dout) read from the memory cells 10 by the column driver 45 is output to the output circuit 48 . The output circuit 48 has a function of holding Dout. Also, the output circuit 48 has a function of outputting Dout to the outside of the storage device 100 . Data output from the output circuit 48 is the signal RDA.

PSW 22 has a function of controlling the supply of VDD to peripheral circuit 31 . PSW 23 has the function of controlling the supply of VHM to row driver 43 . Here, the high power supply voltage of the memory device 100 is VDD, and the low power supply voltage is GND (ground potential). Also, VHM is a high power supply voltage used to drive word lines to a high level and is higher than VDD. The signal PON1 controls ON/OFF of the PSW22, and the signal PON2 controls ON/OFF of the PSW23. In FIG. 1B, in the peripheral circuit 31, the number of power supply domains to which VDD is supplied is set to one, but may be set to a plurality. In this case, a power switch may be provided for each power domain.

<Configuration Example of Storage Layer 60>
A configuration example of the storage layer 60 having N layers will be described. Each of the N storage layers 60 has a memory array 15 . Also, the memory array 15 has a plurality of memory cells 10 . 1A and 1B show an example in which a memory array 15 has a plurality of memory cells 10 arranged in a matrix of m rows and n columns (where m and n are integers of 2 or more).

Note that rows and columns extend in directions orthogonal to each other. In this embodiment, the X direction is the "row" and the Y direction is the "column", but the X direction may be the "column" and the Y direction the "row".

In FIG. 1B, the memory cell 10 provided in the 1st row and 1st column is indicated as memory cell 10[1,1], and the memory cell 10 provided in the 1st row and nth column is indicated as memory cell 10[1,n]. showing. Further, the memory cell 10 provided in the m-th row and the first column is indicated as memory cell 10[m,1], and the memory cell 10 provided in the m-th row and n-th column is indicated as memory cell 10[m,n]. there is The memory cell 10 provided in the i-th row and the j-th column (i is an integer of 1 to m and j is an integer of 1 to n) is denoted by memory cell 10[i,j].

FIG. 2A is an enlarged perspective block diagram of a portion of the storage layer 60_k. FIG. 2B is a plan view of the portion corresponding to FIG. 2A viewed from the Z direction. Each layer of the memory layer 60 includes n wirings WWL (write word lines) extending in the Y direction (column direction) and n wirings RWL (read word lines) extending in the Y direction (column direction). , has 2A and 2B, the wiring WWL provided in the j-th column is indicated as wiring WWL[j], and the wiring RWL provided in the j-th column is indicated as wiring RWL[j]. The wiring WWL[j] and the wiring RWL[j] are electrically connected to the memory cell 10 provided in the j-th column. Further, the wiring WWL provided in the j+1-th column is indicated as the wiring WWL[j+1], and the wiring RWL provided in the j+1-th column is indicated as the wiring RWL[j+1]. Further, the wiring WWL provided in the j+2-th column is indicated as the wiring WWL[j+2], and the wiring RWL provided in the j+2-th column is indicated as the wiring RWL[j+2]. Further, the wiring WWL provided in the j+3rd column is indicated as the wiring WWL[j+3], and the wiring RWL provided in the j+3rd column is indicated as the wiring RWL[j+3].

The memory layer 60 also has wiring BL (write and read bit lines) and wiring SL (selection line). The wirings BL and the wirings SL extend in the Z direction (vertical direction) and are arranged in a matrix of m rows and R columns. 2A and 2B, the wiring BL and the wiring SL provided in the i-th row and the s-th column (s is an integer of 1 or more and R or less) are replaced with the wiring BL[i, s] and the wiring SL[i, s ].

One wiring BL is electrically connected to two memory cells 10 in the memory layer 60 — k. One wiring SL is electrically connected to two memory cells 10 . By sharing one wiring BL and one wiring SL between two adjacent memory cells 10, the area occupied by the memory array 15 can be reduced. Also, the degree of integration of the memory cells 10 is improved, and the storage capacity of the storage device 100 can be increased.

2A and 2B, the wiring BL[i,s] is electrically connected to the memory cell 10[i,j] and the memory cell 10[i,j+1]. In addition, the wiring BL[i, s+1] is electrically connected to the memory cells 10[i, j+2] and 10[i, j+3]. The wiring BL[i,s] is electrically connected to the memory cell 10[i,2×s−1]_k and the memory cell 10[i,2×s]_k.

2A and 2B, the wiring SL[i, s+1] is electrically connected to the memory cell 10[i, j+1] and the memory cell 10[i, j+2]. Memory cell 10[i,j] is electrically connected to wiring SL[i,s], and memory cell 10[i,j+3] is electrically connected to wiring SL[i,s+2].

The relationship between R indicating the column position and n can be expressed by Equation 1 or Equation 2 when n is an odd number.

R=(n+1)/2 (Formula 1)

n=2×R−1 (Formula 2)

The relationship between R indicating the column position and n can be expressed by Equation 3 or Equation 4 when n is an even number.

R = n/2 (Formula 3)

n=2×R (Formula 4)

s and j indicating the column position can be expressed by Equation 5 or Equation 6 when j is an odd number.

s=(j+1)/2 (Formula 5)

j=2×s−1 (Formula 6)

s and j indicating the column position can be expressed by Equation 7 or Equation 8 when j is an even number.

s=j/2 (Formula 7)

j = 2 x s (Formula 8)

FIG. 3A shows a schematic cross-sectional view of memory cell 10[i,j] and memory cell 10[i,j+1] of storage layer 60_k. FIG. 3B shows a circuit configuration example of FIG. 3A. In addition, in FIG. 3A, a part of the cross-sectional schematic diagram is enlarged and illustrated.

The memory cell 10[i,j] has a transistor M1, a transistor M2, and a capacitive element C. A memory cell including two transistors and one capacitor is also referred to as a 2Tr1C memory cell. Therefore, the memory cell 10 described in this embodiment is a 2Tr1C memory cell.

In the memory cell 10[i,j], the gate of the transistor M1 is electrically connected to the wiring WWL[j], and one of the source and the drain is electrically connected to the wiring BL[i,s]. Note that FIG. 3A shows a configuration example in which part of the wiring WWL[j] functions as the gate of the transistor M1. One electrode of the capacitor C is electrically connected to the wiring RWL[j], and the other electrode is electrically connected to the other of the source and the drain of the transistor M1. Note that FIG. 3A and the like show a configuration example in which part of the wiring RWL[j] functions as one electrode of the capacitor C. As shown in FIG. Further, the gate of the transistor M2 is electrically connected to the other electrode of the capacitor C, one of the source and the drain is electrically connected to the wiring BL[i,s], and the other of the source and the drain is electrically connected to the wiring SL[ i, s].

In the memory cell 10[i, j], the other electrode of the capacitor C, the other of the source or the drain of the transistor M1, and the gate of the transistor M2 are electrically connected to each other, and the region always at the same potential is a “node ND”. call.

In the memory cell 10[i,j+1], the gate of the transistor M1 is electrically connected to the wiring WWL[j+1], and one of the source and the drain is electrically connected to the wiring BL[i,s]. Note that FIG. 3A shows a configuration example in which part of the wiring WWL[j+1] functions as the gate of the transistor M1. One electrode of the capacitor C is electrically connected to the wiring RWL[j+1], and the other electrode is electrically connected to the other of the source and the drain of the transistor M1. Note that in FIG. 3A and the like, a configuration example in which part of the wiring RWL[j+1] functions as one electrode of the capacitor C is shown. Further, the gate of the transistor M2 is electrically connected to the other electrode of the capacitor C, one of the source and the drain is electrically connected to the wiring BL[i,s], and the other of the source and the drain is electrically connected to the wiring SL[ i, s+1].

In memory cell 10[i, j+1], the other electrode of capacitive element C, the other of the source or drain of transistor M1, and the gate of transistor M2 are electrically connected to each other, and a region always at the same potential is called node ND. .

Further, as shown in FIGS. 3A and 3B, transistors having back gates may be used as the transistor M1 and the transistor M2. The gate and the back gate are arranged so as to sandwich the semiconductor channel forming region between the gate and the back gate. The gate and back gate are made of conductors. A back gate can function like a gate. Further, by changing the potential of the back gate, the threshold voltage of the transistor can be changed. The potential of the back gate may be the same as that of the gate, the ground potential, or any other potential.

In addition, since the gate and back gate are made of conductors, they also have a function of preventing an electric field generated outside the transistor from acting on the semiconductor in which the channel is formed (particularly, an electrostatic shielding function against static electricity). That is, it is possible to prevent the electrical characteristics of the transistor from varying due to the influence of an external electric field such as static electricity. Further, by providing the back gate, the amount of change in the threshold voltage of the transistor before and after the BT test can be reduced.

For example, by using a transistor having a back gate as the transistor M1, the influence of an external electric field is reduced and the off state can be stably maintained. Therefore, data written to the node ND can be stably held. By providing the back gate, the operation of the memory cell 10 is stabilized, and the reliability of the memory device including the memory cell 10 can be improved.

As a semiconductor layer in which channels of the transistor M1 and the transistor M2 are formed, a single crystal semiconductor, a polycrystalline semiconductor, a microcrystalline semiconductor, an amorphous semiconductor, or the like can be used alone or in combination. For example, silicon, germanium, or the like can be used as the semiconductor material. Compound semiconductors such as silicon germanium, silicon carbide, gallium arsenide, oxide semiconductors, and nitride semiconductors may also be used.

Note that transistors in which an oxide semiconductor, which is a kind of metal oxide, is used for a semiconductor layer in which a channel is formed (also referred to as “OS transistors”) are preferably used as the transistors M1 and M2. An oxide semiconductor has a bandgap of 2 eV or more, and thus has a significantly low off-state current. Therefore, power consumption of the memory cell 10 can be reduced. Therefore, the power consumption of the memory device 100 including the memory cells 10 can be reduced.

A memory cell including an OS transistor can also be called an "OS memory." Further, the memory device 100 including the memory cell can also be called an "OS memory".

In addition, the OS transistor operates stably even in a high-temperature environment and has little characteristic variation. For example, the off current hardly increases even in a high temperature environment. Specifically, the off current hardly increases even under an environmental temperature of room temperature or higher and 200° C. or lower. Also, the on-current is less likely to decrease even in a high-temperature environment. Therefore, the OS memory can operate stably even in a high-temperature environment and obtain high reliability.

Further, in the cross-sectional configuration example shown in FIG. 3A, the conductor 242a (the conductor 242a1 and the conductor 242a2) including the region functioning as one of the source electrode and the drain electrode of the transistor M1 is the oxide 230 (the conductor 242a2) functioning as a semiconductor layer. It extends beyond oxide 230a, oxide 230b). Therefore, the conductor 242 also functions as wiring. In FIG. 3A, each part of the upper surface, side surface, and lower surface of the conductor 242a is in electrical contact with the wiring BL[i,s] extending in the Z direction.

Since the wiring BL[i,s] is in direct contact with at least one of the top surface, the side surface, and the bottom surface of the conductor 242a, there is no need to provide a separate electrode for connection, so that the area occupied by the memory array 15 can be reduced. Also, the degree of integration of the memory cells 10 is improved, and the storage capacity of the storage device 100 can be increased. Note that the wiring BL[i,s] is preferably in contact with two or more of the top surface, the side surface, and the bottom surface of the conductor 242a. The contact resistance between the wiring BL[i,s] and the conductor 242a can be reduced when the wiring BL[i,s] is in contact with multiple surfaces of the conductor 242a.

In addition, the conductor 242b (the conductor 242b1 and the conductor 242b2) including the region functioning as the other of the source and the drain of the transistor M1 extends over the oxide 230 (the oxide 230a and the oxide 230b) functioning as a semiconductor layer. extended. In the cross-sectional configuration example shown in FIG. 3A, a conductor 366 is provided in contact with the lower surface of the conductor 242b. In addition, the conductor 242b and the gate of the transistor M2 are electrically connected through the conductor 366. FIG. Conductor 366 functions as a contact plug.

By providing the conductor 366 in a region overlapping with the conductor 242b and electrically connecting it to the underlying conductor, the connection distance between the two can be shortened. Also, the number of wirings required for configuring the memory cell 10 can be reduced. Therefore, the area occupied by the memory cell 10 can be reduced. Therefore, the storage capacity and storage density of the storage device can be increased.

In addition, one of the source and the drain of the transistor M2 is electrically connected to the wiring BL[i, s] in the same manner as the one of the source and the drain of the transistor M1. Specifically, it is electrically connected to the wiring BL[i,s] through a conductor including a region functioning as one of the source electrode and the drain electrode of the transistor M2. At least one of the top surface, the side surface, and the bottom surface of the conductor is preferably in contact with the wiring BL[i,s], similarly to the transistor M1.

In addition, the other of the source and the drain of the transistor M2 may be electrically connected to the wiring SL[i,s] in the same manner as the one of the source and the drain of the transistor M1. Specifically, it may be electrically connected to the wiring SL[i,s] through a conductor including a region functioning as the other of the source electrode and the drain electrode of the transistor M2. At least one of the top surface, side surface, and bottom surface of the conductor is preferably in contact with the wiring SL[i,s].

A cross-sectional configuration of the memory cell 10 will be described in detail in another embodiment.

FIG. 4 shows a cross-sectional configuration example of the memory layer 60 in which the memory layers 60_1 to 60_5 are stacked. FIG. 5 shows a circuit configuration example of FIG. 4 and 5, the memory cells 10[i,j] included in the memory layers 60_1 to 60_5 are indicated as memory cells 10[i,j]_1 to 10[i,j]_5. there is Further, the wiring WWL[j] included in the memory layer 60_5 is indicated as the wiring WWL[j]_5, and the wiring RWL[j] included in the memory layer 60_5 is indicated as the wiring RWL[j]_5. Further, the wiring WWL[j+1] included in the memory layer 60_5 is indicated as the wiring WWL[j+1]_5, and the wiring RWL[j+1] included in the memory layer 60_5 is indicated as the wiring RWL[j+1]_5.

4 and 5 show a configuration example in which five storage layers 60 are stacked, but the number of storage layers 60 stacked is not limited to five. By increasing the number of stacked memory layers 60 , the memory capacity of the memory device 100 can be increased without increasing the area occupied by the memory cells 10 . Therefore, the area occupied by each bit is reduced, and a small storage device with a large storage capacity can be realized.

<Operation Example of Memory Cell 10>
Next, a data write operation example and a data read operation example of the memory cell 10 will be described. In this embodiment mode, normally-off n-channel transistors are used for the transistor M1 and the transistor M2. FIG. 6 is a timing chart for explaining an operation example of the memory cell 10. FIG. 7A, 7B, 8A, and 8B are circuit diagrams for explaining an operation example of the memory cell 10. FIG.

In the drawings and the like, "H" indicating potential H or "L" indicating potential L may be added adjacent to the wiring and the electrode to indicate the potential of the wiring and the electrode. In addition, "H" or "L" may be appended to the wiring and electrode in which the potential change occurs. In addition, when a transistor is in an off state, an “x” symbol may be added over the transistor in some cases.

First, in the period T0, the potential of the wiring WWL is VSS, the potential of the wiring RWL, the wiring BL, and the node ND is L, and the potential of the wiring SL is H (see FIG. 6). In this embodiment and the like, VSS is set to a potential of 2L or lower, which will be described later. It is also assumed that GND is supplied to the back gates of the transistor M1 and the transistor M2.

[Data write operation]
In the period T1, an H potential is supplied to the wirings RWL, WWL, and BL (see FIGS. 6 and 7A). Then, the transistor M1 is turned on, and the H potential is written to the node ND as data indicating "1". More precisely, the node ND is supplied with such an amount of charge that the potential of the node ND becomes H potential.

Further, since the gate, source, and drain of the transistor M2 are all at the same potential (H potential), the transistor M2 is turned off.

[Holding operation]
In the period T2, VSS is supplied to the wiring WWL and the potential L is supplied to the wiring RWL. Then, the transistor M1 is turned off, and the node ND becomes floating. Therefore, data (charge) written to the node ND is held (see FIGS. 6 and 7B).

At this time, since the node ND is in a floating state, the potential of the node ND also changes following the potential change of the wiring RWL. Note that the amount of potential change at the node ND is determined by the capacitance ratio between the capacitance element C and the gate capacitance of the transistor M2. For example, when the capacitance value of the capacitor C is sufficiently larger than the gate capacitance of the transistor M2, the same potential change as that of the wiring RWL occurs at the node ND.

In this embodiment, it is assumed that the capacitance value of the capacitive element C is sufficiently larger than the gate capacitance of the transistor M2. Therefore, when the potential of the wiring RWL changes from the potential H to the potential L, the potential of the node ND also changes from the potential H to the potential L.

Note that when the potential L is supplied to the node ND as data indicating “0” in the period T1, the potential of the node ND in the period T2 is a potential lower than the potential L by the potential difference between the potential H and the potential L (“potential 2L”). In order to prevent the transistor M1 from being turned on when the potential of the node ND becomes 2L, VSS supplied to the gate of the transistor M1 needs to be 2L or lower.

As described above, the OS transistor has extremely low off-state current. By using an OS transistor as the transistor M1, data written to the node ND can be held for a long time. Therefore, there is no need to refresh the node ND, and the power consumption of the memory cell 10 can be reduced. Therefore, power consumption of the storage device 100 can be reduced.

In addition, an OS transistor has a higher drain breakdown voltage than a transistor using silicon for a semiconductor layer in which a channel is formed (also referred to as a Si transistor). Therefore, by using an OS transistor as the transistor M1, the range of the potential held in the node ND can be widened. Therefore, multilevel data or analog data can be held in the node ND.

[Read operation]
In the period T3, the potential H is precharged (H (Pre)) to the wiring BL. That is, the wiring BL is brought into a floating state while it is kept at the potential H (see FIGS. 6 and 8A).

Next, in the period T4, the potential H is supplied to the wiring RWL and the potential L is supplied to the wiring SL (see FIGS. 6 and 8B). When the potential of the wiring RWL changes from the potential L to the potential H, the potential of the node ND also changes from the potential L to the potential H. When the potential of the node ND becomes the potential H and the potential of the wiring SL becomes the potential L, the transistor M2 is turned on. When the transistor M2 is turned on, the wiring BL and the wiring SL are brought into electrical continuity, and the potential of the wiring BL changes from the H potential to the L potential.

On the other hand, when the L potential is written to the node ND as data indicating "0", the transistor M2 is not turned on even if the L potential is supplied to the wiring SL. Therefore, data written to the memory cell 10 can be read by detecting a change in the potential of the wiring BL when the L potential is supplied to the wiring SL.

Since the memory cell 10 using the OS transistor writes electric charges to the node ND via the OS transistor, it does not require the high voltage required in the conventional flash memory, and high-speed write operation can be realized. In addition, since no charge is injected into or extracted from the floating gate or charge trapping layer, the memory cell 10 using the OS transistor can write and read data substantially unlimited times. Unlike a flash memory, the memory cell 10 using an OS transistor does not exhibit instability due to an increase in electron trapping centers even after repeated rewrite operations. The memory cell 10 using the OS transistor has less deterioration and higher reliability than the conventional flash memory.

The memory cell 10 using an OS transistor does not involve structural changes at the atomic level, unlike magnetic memories or resistance change memories. Therefore, the memory cell 10 using the OS transistor has better rewrite endurance than the magnetic memory and the resistance change memory.

Further, in the memory device 100 of one embodiment of the present invention, the memory cell 10 and the driver circuit layer 50 are electrically connected through the wiring BL having a region extending in the Z direction. Therefore, the routing distance of the wiring BL is short, and wiring resistance and parasitic capacitance are small. In the memory device 100 of one embodiment of the present invention, the wiring resistance and parasitic capacitance of the wiring BL are low, so that the data writing speed and data reading speed are high.

The structure described in this embodiment can be combined as appropriate with any of the structures described in other embodiments.

(Embodiment 2)
In this embodiment, a configuration example of a semiconductor device that can be applied to the memory cell 10 of one embodiment of the present invention will be described with reference to drawings. The semiconductor device described in this embodiment includes a transistor and a capacitor.

<Structure example of semiconductor device>
A structural example of a semiconductor device including a transistor and a capacitor is described with reference to FIGS. 9A to 9D are a top view and cross-sectional views of a semiconductor device including a transistor 200a, a transistor 200b, a capacitor 150a, and a capacitor 150b.

The transistor 200a or the transistor 200b can be used as the transistor M1 and the transistor M2 described in the above embodiment. Further, the capacitor 150a and the capacitor 150b can be used as the capacitor C described in the above embodiment.

FIG. 9A is a plan view of the semiconductor device. 9B to 9D are cross-sectional views of the semiconductor device. Here, FIG. 9B is a cross-sectional view of a portion indicated by a dashed-dotted line A1-A2 in FIG. 9A, a cross-sectional view of the transistor 200a and the transistor 200b in the channel length direction, and a cross-sectional view of the capacitor 150a and the capacitor 150b. But also. FIG. 9C is a cross-sectional view of the portion indicated by the dashed-dotted line A3-A4 in FIG. 9A, and is a cross-sectional view of the transistor 200a in the channel width direction. FIG. 9D is a cross-sectional view of the portion indicated by the dashed-dotted line A5-A6 in FIG. 9A, and is a cross-sectional view of the transistor 200a and the capacitor 150a in the channel width direction. In addition, in the plan view of FIG. 9A, description of some components is omitted for clarity of the drawing.

The X direction shown in FIG. 9A is parallel to the channel length direction of the transistor 200a and the channel length direction of the transistor 200b.

A semiconductor device of one embodiment of the present invention includes an insulator 214 over a substrate (not illustrated), transistors 200a, 200b, capacitors 150a, and 150b over the insulator 214, and transistors 200a and 200b. An insulator 280 on the provided insulator 275, an insulator 282 on the capacitive element 150a, the capacitive element 150b, and the insulator 280, an insulator 285 on the insulator 282, and a conductor 240 (conductor 240a and conductors 240b). The insulator 214, the insulator 280, the insulator 282, and the insulator 285 function as interlayer films. As shown in FIG. 9B, at least part of each of the transistor 200a, the transistor 200b, the capacitor 150a, and the capacitor 150b is buried in the insulator 280 and arranged.

Here, the transistor 200a and the transistor 200b each have an oxide 230 functioning as a semiconductor layer, a conductor 260 functioning as a first gate (also referred to as a top gate) electrode, and a second gate (also referred to as a back gate). It has a conductor 205 functioning as an electrode, a conductor 242a functioning as one of a source electrode and a drain electrode, and a conductor 242b functioning as the other of the source electrode and the drain electrode. It also has an insulator 253 and an insulator 254 that function as a first gate insulator. It also has an insulator 222 and an insulator 224 that act as a second gate insulator. Note that the gate insulator is sometimes called a gate insulating layer or a gate insulating film.

Note that since the transistor 200a and the transistor 200b have the same structure, the transistor 200a and the transistor 200b are hereinafter referred to as the transistor 200 when common items for the transistor 200a and the transistor 200b are described. sometimes.

The first gate electrode and first gate insulating film are arranged in openings 258 formed in insulator 280 and insulator 275 . That is, conductor 260 , insulator 254 , and insulator 253 are positioned within opening 258 .

Each of the capacitive element 150a and the capacitive element 150b includes a conductor 242b functioning as a lower electrode, insulators 275, 153, and 154 functioning as dielectrics, and a conductor 160 functioning as an upper electrode. have In other words, the capacitive element 150a and the capacitive element 150b each constitute an MIM (Metal-Insulator-Metal) capacitance.

Note that since the capacitive element 150a and the capacitive element 150b have the same configuration, hereinafter, when describing items common to the capacitive element 150a and the capacitive element 150b, the symbols added to the reference numerals are omitted, and the capacitive element 150b may be described as

A portion of the top electrode and dielectric of capacitive element 150 is disposed within opening 158 formed in insulator 280 . That is, conductor 160 , insulator 154 , and insulator 153 are positioned within opening 158 .

In addition, the semiconductor device of one embodiment of the present invention includes conductors 240 (the conductors 240a and 240b). The conductor 240 has a region in contact with the conductor 242a. The conductor 240 has a region in contact with the conductor 242a and is electrically connected to the transistor 200 to function as a plug.

In addition, the semiconductor device of one embodiment of the present invention includes the insulator 210 and the conductor 209 between the substrate (not shown) and the insulator 214 . The conductor 209 is arranged to be embedded in the insulator 210 . Conductor 209 has a region in contact with conductor 240 .

In addition, the semiconductor device of one embodiment of the present invention may include an insulator 212 between the insulator 210 and the conductor 209 and the insulator 214 .

A semiconductor device including the transistor 200 and the capacitor 150 described in this embodiment can be used as a memory cell of a memory device. At this time, the conductor 240 may be electrically connected to the sense amplifier. Here, as shown in FIG. 9A, at least part of the capacitor 150 overlaps with the oxide 230 included in the transistor 200 . Therefore, since the capacitive element 150 can be provided without greatly increasing the occupied area in plan view, the semiconductor device according to this embodiment can be miniaturized or highly integrated.

In addition, the semiconductor device described in this embodiment has a line-symmetrical structure with the dashed-dotted line A7-A8 shown in FIG. 9A as an axis of symmetry. The conductor 242a serves also as one of the source electrode and the drain electrode of the transistor 200a and one of the source electrode and the drain electrode of the transistor 200b. Thus, by connecting two transistors, two capacitive elements, and plugs in the above configuration, a semiconductor device that can be miniaturized or highly integrated can be provided.

[Transistor 200]
9A to 9D, the transistor 200 includes an insulator 216 over an insulator 214, conductors 205 (a conductor 205a and a conductor 205b) embedded in the insulator 216, Insulator 222 over insulator 216 and over conductor 205, insulator 224 over insulator 222, oxide 230a over insulator 224, oxide 230b over oxide 230a, and oxide 230b Conductor 242a (conductor 242a1 and conductor 242a2) and conductor 242b (conductor 242b1 and conductor 242b2), insulator 253 over oxide 230b, insulator 254 over insulator 253, and insulator 254 Conductor 260 (conductor 260a and conductor 260b) that overlies and overlaps part of oxide 230b, insulator 222, insulator 224, oxide 230a, oxide 230b, and conductors and an insulator 275 disposed on 242a and on conductor 242b.

Note that in this specification and the like, the oxide 230a and the oxide 230b are collectively referred to as the oxide 230 in some cases. In addition, the conductor 242a and the conductor 242b are collectively referred to as the conductor 242 in some cases.

Insulator 280 and insulator 275 are provided with openings 258 down to oxide 230b. That is, it can be said that the opening 258 has a region that overlaps with the oxide 230b. In addition, it can be said that the insulator 275 has an opening that overlaps with the opening of the insulator 280 . Also, an insulator 253 , an insulator 254 and a conductor 260 are arranged in the opening 258 . That is, the conductor 260 has a region overlapping with the oxide 230b with the insulators 253 and 254 interposed therebetween. A conductor 260 , an insulator 253 , and an insulator 254 are provided between the conductor 242 a and the conductor 242 b in the channel length direction of the transistor 200 . The insulator 254 has a region in contact with the side surface of the conductor 260 and a region in contact with the bottom surface of the conductor 260 . Note that the top surface of the insulator 222 is exposed in a region of the opening 258 that does not overlap with the oxide 230, as shown in FIG. 9C.

Oxide 230 preferably includes oxide 230a overlying insulator 224 and oxide 230b overlying oxide 230a. By providing the oxide 230a under the oxide 230b, diffusion of impurities from a structure formed below the oxide 230a to the oxide 230b can be suppressed.

Note that although the transistor 200 has a structure in which the oxide 230 has two layers of the oxide 230a and the oxide 230b stacked, the present invention is not limited to this. For example, a single layer of the oxide 230b or a layered structure of three or more layers may be provided, or each of the oxides 230a and 230b may have a layered structure.

Conductor 260 functions as a first gate electrode, and conductor 205 functions as a second gate electrode. Insulators 253 and 254 function as first gate insulators, and insulators 222 and 224 function as second gate insulators. In addition, the conductor 242a functions as one of the source electrode and the drain electrode, and the conductor 242b functions as the other of the source electrode and the drain electrode. At least part of the region of the oxide 230 overlapping with the conductor 260 functions as a channel formation region.

Here, FIG. 11A shows an enlarged view of the vicinity of the channel formation region in FIG. 9B. As shown in FIG. 11A, in a cross-sectional view of the transistor 200 in the channel length direction, the distance L2 between the conductors 242a and 242b is preferably smaller than the width of the opening 258. As shown in FIG. Here, the width of the opening 258 is the distance L1 between the interface of the insulator 280 and the insulator 253 on the conductor 242a side and the interface of the insulator 280 and the insulator 253 on the conductor 242b side shown in FIG. 11A. handle. Although details will be described later, channel etching of the conductors 242a and 242b is performed after the opening 258 is formed in this embodiment mode. With such a configuration, the distance L2 between the conductor 242a and the conductor 242b can be relatively easily adjusted to a very fine structure (for example, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less). , or 10 nm or less, and 1 nm or more, or 5 nm or more). In addition, since the conductor 260 has a region with a distance L1 that is longer than the distance L2, it is possible to suppress a decrease in the conductivity of the conductor 260 located in the region with the distance L1 and allow the conductor 260 to function as a wiring. can.

11A and 9C, the insulator 224, the oxide 230, the conductor 242, and the insulator 275 are placed in the opening having the insulator 222 as the bottom surface and the insulator 280 as the side surface. It can also be regarded as a shape in which part of the containing structure protrudes. Further, in the structure including the insulator 224, the oxide 230, the conductor 242, and the insulator 275, the region of the oxide 230 between the conductors 242a and 242b can be considered exposed.

As shown in FIGS. 11A and 9C, insulator 253 is provided in contact with the bottom and inner walls of opening 258 . Thus, insulator 253 has a top surface of insulator 222, side surfaces of insulator 224, side surfaces of oxide 230a, top and side surfaces of oxide 230b, side surfaces of conductors 242a and 242b, side surfaces of insulator 275, and insulating surfaces. It contacts at least a portion of each of the side surfaces of body 280 and the bottom surface of insulator 254 . An insulator 254 and a conductor 260 are stacked over the insulator 253 . Therefore, an insulator 253 , an insulator 254 and a conductor 260 are provided to cover the conductor 242 and the insulator 275 partially protruding into the opening 258 .

A channel forming region is formed in the region of distance L2 in oxide 230b. Therefore, the channel formation region of the transistor 200 has a very fine structure. As a result, the ON current of the transistor 200 is increased, and the frequency characteristics can be improved.

Note that the shape of the opening 258 is not limited to the shape shown in FIG. 11A. As shown in FIG. 11B, opening 258 may have a shape with equal distance L1 and distance L2. At this time, the side surface of the conductor 242a and the side surface of the insulator 275 approximately match the side surface of the insulator 280, as shown in FIG. 11B. Also, the side surface of the conductor 242b and the side surface of the insulator 275 approximately match the side surface of the insulator 280. As shown in FIG. With such a structure, manufacturing steps of a semiconductor device can be simplified and productivity can be improved. In addition, when a plurality of transistors 200 are provided, the area can be reduced and the density can be increased.

Note that FIG. 11B shows a configuration in which the side walls of the opening 258 are substantially perpendicular to the upper surface of the insulator 222, but the present invention is not limited to this. As shown in FIG. 11C, the sidewalls of opening 258 may be tapered. By tapering the side wall of the opening 258, coverage with the insulator 253 or the like is improved in subsequent steps, and defects such as voids can be reduced.

Note that in this specification and the like, a tapered shape refers to a shape in which at least part of a side surface of a structure is inclined with respect to a substrate surface. For example, it is preferable to have a region where the angle formed by the inclined side surface of the structure and the substrate surface (bottom surface) (hereinafter sometimes referred to as taper angle) is less than 90°. The side surfaces and the substrate surface (bottom surface) of the structure are not necessarily completely flat, and may be substantially planar with a fine curvature or substantially planar with fine unevenness.

As shown in FIG. 11A, the oxide 230b includes a region 230bc functioning as a channel formation region of the transistor 200, and regions 230ba and 230bb functioning as a source region or a drain region and provided to sandwich the region 230bc. have. At least a portion of the region 230bc overlaps the conductor 260 . In other words, the region 230bc is provided in a region between the conductors 242a and 242b. The region 230ba is provided so as to overlap with the conductor 242a, and the region 230bb is provided so as to overlap with the conductor 242b.

The region 230bc functioning as a channel forming region is a high-resistance region with a lower carrier concentration because it has less oxygen vacancies or a lower impurity concentration than the regions 230ba and 230bb. Thus, region 230bc can be said to be i-type (intrinsic) or substantially i-type.

Further, the region 230ba and the region 230bb functioning as a source region or a drain region have a large amount of oxygen vacancies or a high concentration of impurities such as hydrogen, nitrogen, and metal elements, so that the carrier concentration is increased and the resistance is lowered. area. That is, the regions 230ba and 230bb are n-type regions having a higher carrier concentration and a lower resistance than the region 230bc.

Here, as shown in FIG. 11A, the opposing sides of conductor 242a and conductor 242b are preferably substantially perpendicular to the top surface of oxide 230b. With such a configuration, the side end portion of the region 230ba formed under the conductor 242a on the side of the region 230bc is prevented from excessively receding from the side end portion of the conductor 242a on the side of the region 230bc. can. Similarly, it is possible to prevent the side end portion of the region 230bb formed under the conductor 242b on the side of the region 230bc from excessively receding from the side end portion of the conductor 242b on the side of the region 230bc. This can reduce the formation of so-called Loff regions between the regions 230ba and 230bc and between the regions 230bb and 230bc. Here, the side end portion of the region 230ba on the side of the region 230bc recedes means that the side end portion of the region 230ba is located closer to the conductor 240 than the side surface of the conductor 242a on the side of the region 230bc. In addition, the fact that the side end portion of the region 230bb on the side of the region 230bc recedes means that the side end portion of the region 230bb is positioned closer to the conductor 160 than the side surface of the conductor 242b on the side of the region 230bc.

As described above, the frequency characteristics of the transistor 200 can be improved, and the operation speed of the semiconductor device according to one embodiment of the present invention can be improved. For example, when the semiconductor device according to one embodiment of the present invention is used as a memory cell of a memory device, writing speed and reading speed can be improved.

Note that the carrier concentration of the region 230bc functioning as a channel formation region is preferably 1×10 ¹⁸ cm ⁻³ or less, more preferably less than 1×10 ¹⁷ cm ⁻³ , and 1×10 ¹⁶ cm ^{−3 .} It is more preferably less than ³ , more preferably less than 1×10 ¹³ cm ⁻³ , even more preferably less than 1×10 ¹² cm ⁻³ . Also, the lower limit of the carrier concentration of the region 230bc functioning as a channel formation region is not particularly limited, but can be set to 1×10 ⁻⁹ cm ⁻³ , for example.

Further, between the region 230bc and the region 230ba or between the region 230bc and the region 230bb, the carrier concentration is equal to or lower than the carrier concentration of the regions 230ba and 230bb and equal to or lower than the carrier concentration of the region 230bc. A region may be formed that is higher than . That is, the region functions as a junction region between the regions 230bc and 230ba or between the regions 230bc and 230bb. The bonding region may have a hydrogen concentration equal to or lower than that of the regions 230ba and 230bb and equal to or higher than that of the region 230bc. In addition, the bonding region may have oxygen vacancies equal to or less than those of the regions 230ba and 230bb and equal to or greater than those of the region 230bc.

Although FIG. 11A shows an example in which the regions 230ba, 230bb, and 230bc are formed in the oxide 230b, the present invention is not limited to this. For example, each of the above regions may be formed up to oxide 230a as well as oxide 230b.

Also, in the oxide 230, it may be difficult to clearly detect boundaries between regions. The concentrations of metal elements and impurity elements such as hydrogen and nitrogen detected in each region are not limited to stepwise changes for each region, and may change continuously within each region. In other words, the closer the region is to the channel formation region, the lower the concentrations of the metal elements and the impurity elements such as hydrogen and nitrogen.

In the transistor 200, a metal oxide functioning as a semiconductor (hereinafter also referred to as an oxide semiconductor) is preferably used for the oxide 230 (the oxide 230a and the oxide 230b) including a channel formation region.

Further, the bandgap of the metal oxide functioning as a semiconductor is preferably 2 eV or more, more preferably 2.5 eV or more. The off-state current of the transistor can be reduced by using a metal oxide with a large bandgap.

Metal oxides such as indium oxide, gallium oxide, and zinc oxide are preferably used as the oxide 230, for example. Moreover, as the oxide 230, it is preferable to use, for example, a metal oxide containing two or three elements selected from indium, the element M, and zinc. Element M includes gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium. One or more selected from In particular, the element M is preferably one or more selected from aluminum, gallium, yttrium, and tin. Note that a metal oxide containing indium, the element M, and zinc is sometimes referred to as an In-M-Zn oxide.

The oxide 230 preferably has a laminated structure of multiple oxide layers with different chemical compositions. For example, in the metal oxide used for the oxide 230a, the atomic ratio of the element M to the main component metal element is the same as the atomic ratio of the element M to the main component metal element in the metal oxide used for the oxide 230b. Larger is preferable. Moreover, in the metal oxide used for the oxide 230a, the atomic ratio of the element M to In is preferably higher than the atomic ratio of the element M to In in the metal oxide used for the oxide 230b. With this structure, diffusion of impurities and oxygen from structures formed below the oxide 230a to the oxide 230b can be suppressed.

In addition, the atomic ratio of In to the element M in the metal oxide used for the oxide 230b is preferably higher than the atomic ratio of In to the element M in the metal oxide used for the oxide 230a. With such a structure, the transistor 200 can have high on-state current and high frequency characteristics.

In addition, since the oxide 230a and the oxide 230b have a common element other than oxygen as a main component, the defect level density at the interface between the oxide 230a and the oxide 230b can be reduced. The defect level density at the interface between oxide 230a and oxide 230b can be reduced. Therefore, the influence of interface scattering on carrier conduction is reduced, and the transistor 200 can obtain a large on-current and high frequency characteristics.

Specifically, as the oxide 230a, In:M:Zn=1:3:4 [atomic ratio] or a composition in the vicinity thereof, or In:M:Zn=1:1:0.5 [atomic ratio ] or a metal oxide having a composition in the vicinity thereof may be used. In addition, the oxide 230b has a composition of In:M:Zn=1:1:1 [atomic ratio] or its vicinity, In:M:Zn=1:1:1.2 [atomic ratio] or its vicinity composition, In:M:Zn=1:1:2 [atomic ratio] or a composition in the vicinity thereof, or In:M:Zn=4:2:3 [atomic ratio] or a composition in the vicinity thereof. You can use things. It should be noted that the neighboring composition includes a range of ±30% of the desired atomic number ratio. Moreover, as the element M, it is preferable to use gallium. In the case where a single layer of the oxide 230b is provided as the oxide 230, a metal oxide that can be used for the oxide 230a may be used as the oxide 230b.

When the metal oxide is deposited by a sputtering method, the above atomic ratio is not limited to the atomic ratio of the deposited metal oxide, and the atomic ratio of the sputtering target used for the deposition of the metal oxide. may be

The oxide 230b preferably has crystallinity. In particular, CAAC-OS (c-axis aligned crystal oxide semiconductor) is preferably used as the oxide 230b.

CAAC-OS is a metal oxide that has a dense structure with high crystallinity and few impurities and defects (eg, oxygen vacancies). In particular, after the metal oxide is formed, heat treatment is performed at a temperature at which the metal oxide is not polycrystallized (for example, 400° C. or more and 600° C. or less), so that the CAAC-OS has a dense structure with higher crystallinity. can be By increasing the density of the CAAC-OS in this manner, diffusion of impurities or oxygen in the CAAC-OS can be further reduced.

In addition, since it is difficult to confirm a clear crystal grain boundary in CAAC-OS, it can be said that a decrease in electron mobility due to a crystal grain boundary is unlikely to occur. Therefore, metal oxides with CAAC-OS have stable physical properties. Therefore, a metal oxide including CAAC-OS is heat resistant and highly reliable.

Further, by using a crystalline oxide such as CAAC-OS as the oxide 230b, extraction of oxygen from the oxide 230b by the source electrode or the drain electrode can be suppressed. Accordingly, extraction of oxygen from the oxide 230b can be reduced even if heat treatment is performed, so that the transistor 200 is stable against high temperatures (so-called thermal budget) in the manufacturing process.

In a transistor including an oxide semiconductor, if impurities and oxygen vacancies are present in a region where a channel is formed in the oxide semiconductor, electrical characteristics are likely to vary, and reliability may be degraded. In addition, hydrogen in the vicinity of oxygen vacancies may form defects in which hydrogen enters oxygen vacancies (hereinafter sometimes referred to as V _OH ) to generate electrons serving as carriers. Therefore, if oxygen vacancies are included in the region where the channel is formed in the oxide semiconductor, the transistor has normally-on characteristics (a channel exists even if no voltage is applied to the gate electrode, and current flows through the transistor). flow characteristics). Therefore, impurities, oxygen vacancies, and _VOH are preferably reduced as much as possible in a region where a channel is formed in the oxide semiconductor. In other words, the region in which the channel is formed in the oxide semiconductor preferably has a reduced carrier concentration and is i-type (intrinsic) or substantially i-type.

In contrast, an insulator containing oxygen that is released by heating (hereinafter sometimes referred to as excess oxygen) is provided in the vicinity of the oxide semiconductor, and heat treatment is performed so that the oxide semiconductor is converted from the insulator. Oxygen can be supplied and oxygen vacancies and _VOH can be reduced. However, when an excessive amount of oxygen is supplied to the source region or the drain region, the on-state current or the field-effect mobility of the transistor 200 might decrease. Furthermore, variations in the amount of oxygen supplied to the source region or the drain region within the substrate surface cause variations in the characteristics of the semiconductor device having transistors. In addition, when oxygen supplied from the insulator to the oxide semiconductor diffuses into a conductor such as a gate electrode, a source electrode, or a drain electrode, the conductor is oxidized and the conductivity is impaired. It may adversely affect the electrical characteristics and reliability of the transistor.

Therefore, in the oxide semiconductor, the region 230bc functioning as a channel formation region preferably has a reduced carrier concentration and is i-type or substantially i-type. Region 230bb has a high carrier concentration and is preferably n-type. In other words, oxygen vacancies and V _OH in the oxide semiconductor region 230bc are preferably reduced. Also, it is preferable not to supply an excessive amount of oxygen to the regions 230ba and 230bb, and to prevent an excessive decrease in the amount of _VOH in the regions 230ba and 230bb. In addition, it is preferable to employ a structure in which a decrease in conductivity of the conductor 260, the conductor 242a, and the conductor 242b is suppressed. For example, it is preferable to employ a structure in which oxidation of the conductor 260, the conductor 242a, and the conductor 242b is suppressed. Note that hydrogen in the oxide semiconductor can form V _OH ; therefore, the concentration of hydrogen needs to be reduced in order to reduce the amount of V _OH .

Therefore, in this embodiment, the semiconductor device is configured such that the hydrogen concentration in the region 230bc is reduced, the oxidation of the conductors 242a, 242b, and 260 is suppressed, and the regions 230ba and 230bb are The configuration is such that the decrease in the hydrogen concentration is suppressed.

In order to reduce the hydrogen concentration in the region 230bc, the insulator 253 preferably has a function of trapping hydrogen and fixing hydrogen. As shown in FIG. 9C, insulator 253 has a region that contacts region 230bc of oxide 230b. With this structure, the concentration of hydrogen in the region 230bc of the oxide 230b can be reduced. Therefore, the _VOH in the region 230bc can be reduced and the region 230bc can be i-type or substantially i-type.

A metal oxide having an amorphous structure is given as an insulator having a function of trapping and fixing hydrogen. For example, it is preferable to use metal oxides such as magnesium oxide, or oxides containing one or both of aluminum and hafnium. Oxygen atoms in metal oxides having such an amorphous structure have dangling bonds, and the dangling bonds sometimes have the property of capturing or fixing hydrogen. That is, it can be said that a metal oxide having an amorphous structure has a high ability to capture or fix hydrogen.

The insulator 253 and the insulator 153 included in the capacitor 150 are formed using the same insulating film. That is, the insulator 253 and the insulator 153 have the same material. Also, the insulator 153 functions as a dielectric of the capacitor 150 . Therefore, insulator 153 preferably uses a high dielectric constant (high-k) material. At this time, insulator 253 includes a high-k material. An example of a high-k material is an oxide containing one or both of aluminum and hafnium. By using a high-k material for the insulator 253, the gate potential applied during transistor operation can be reduced while maintaining the physical thickness of the gate insulator. Also, the equivalent oxide thickness (EOT) of the insulator that functions as the gate insulator can be reduced.

For the above reasons, an oxide containing one or both of aluminum and hafnium is preferably used as the insulator 253, and an oxide having an amorphous structure and containing one or both of aluminum and hafnium is more preferably used. It is more preferable to use hafnium oxide having a structure. In this embodiment, hafnium oxide is used as the insulator 253 . In this case, the insulator 253 is an insulator containing at least oxygen and hafnium. Further, the hafnium oxide has an amorphous structure. In this case, insulator 253 has an amorphous structure.

In order to suppress oxidation of the conductors 242a, 242b, and 260, barrier insulators against oxygen are preferably provided near the conductors 242a, 242b, and 260, respectively. In the semiconductor device described in this embodiment, the insulators are the insulators 253, 254, and 275, for example.

Note that in this specification and the like, a barrier insulator refers to an insulator having a barrier property. In this specification and the like, the term "barrier property" refers to a function of suppressing diffusion of a corresponding substance (also referred to as low permeability). Alternatively, the corresponding substance has the function of capturing and fixing (also called gettering).

Barrier insulators against oxygen include oxides containing one or both of aluminum and hafnium, magnesium oxide, gallium oxide, indium gallium zinc oxide, silicon nitride, and silicon oxynitride. Examples of oxides of one or both of aluminum and hafnium include aluminum oxide, hafnium oxide, oxides containing aluminum and hafnium (hafnium aluminate), and oxides containing hafnium and silicon (hafnium silicate). For example, the insulator 253, the insulator 254, and the insulator 275 may each have a single layer or a stacked layer of barrier insulators against oxygen.

The insulator 253 preferably has a barrier property against oxygen. Note that the insulator 253 should be at least less permeable to oxygen than the insulator 280 . The insulator 253 has regions in contact with the side surface of the conductor 242a and the side surface of the conductor 242b. Since the insulator 253 has a barrier property against oxygen, the side surfaces of the conductors 242a and 242b are oxidized and formation of an oxide film on the side surfaces can be suppressed. Accordingly, a decrease in on-state current or a decrease in field-effect mobility of the transistor 200 can be suppressed.

The insulator 253 is provided in contact with top and side surfaces of the oxide 230 b , side surfaces of the oxide 230 a , side surfaces of the insulator 224 , and top surface of the insulator 222 . Since the insulator 253 has a barrier property against oxygen, oxygen can be suppressed from being released from the region 230bc of the oxide 230b when heat treatment or the like is performed. Therefore, formation of oxygen vacancies in the oxides 230a and 230b can be reduced.

Conversely, even if the insulator 280 contains an excessive amount of oxygen, excessive supply of the oxygen to the oxides 230a and 230b can be suppressed. Therefore, it is possible to suppress excessive oxidation of the regions 230ba and 230bb to reduce the on current of the transistor 200 or reduce the field effect mobility.

An oxide containing one or both of aluminum and hafnium can be suitably used as the insulator 253 because it has a barrier property against oxygen.

The insulator 254 preferably has a barrier property against oxygen. Insulator 254 is provided between region 230bc of oxide 230 and conductor 260 and between insulator 280 and conductor 260 . With this structure, diffusion of oxygen contained in the region 230bc of the oxide 230 into the conductor 260 and formation of oxygen vacancies in the region 230bc of the oxide 230 can be suppressed. In addition, oxygen contained in the oxide 230 and oxygen contained in the insulator 280 diffuse into the conductor 260, so that oxidation of the conductor 260 can be suppressed. Note that the insulator 254 should be at least less permeable to oxygen than the insulator 280 . For example, silicon nitride is preferably used as the insulator 254 . In this case, the insulator 254 is an insulator containing at least nitrogen and silicon.

The insulator 275 preferably has a barrier property against oxygen. The insulator 275 is provided between the insulator 280 and the conductors 242a and 242b. With this structure, diffusion of oxygen contained in the insulator 280 to the conductors 242a and 242b can be suppressed. Therefore, the oxygen contained in the insulator 280 can prevent the conductors 242a and 242b from being oxidized to increase the resistivity and reduce the on-current. Note that the insulator 275 may be at least less permeable to oxygen than the insulator 280 . For example, silicon nitride is preferably used as the insulator 275 . In this case, the insulator 275 is an insulator containing at least nitrogen and silicon.

In order to suppress reduction in the hydrogen concentration in the regions 230ba and 230bb, it is preferable to provide a barrier insulator against hydrogen in the vicinity of each of the regions 230ba and 230bb. In the semiconductor device described in this embodiment, the barrier insulator against hydrogen is the insulator 275, for example.

Barrier insulators to hydrogen include oxides such as aluminum oxide, hafnium oxide, tantalum oxide, and nitrides such as silicon nitride. For example, the insulator 275 may be a single layer or a stacked layer of the above barrier insulators against hydrogen.

The insulator 275 preferably has a barrier property against hydrogen. The insulator 275 is arranged in contact with the side surface of the region 230ba of the oxide 230b and the side surface of the region 230bb of the oxide 230b. Also, the insulator 275 is arranged between the insulator 253 and the side surface of the region 230ba of the oxide 230b and the side surface of the region 230bb of the oxide 230b. Since the insulator 275 has a barrier property against hydrogen, the insulator 253 can suppress capture and fixation of hydrogen in the regions 230ba and 230bb. Therefore, the regions 230ba and 230bb can be n-type.

With the above structure, the region 230bc functioning as a channel forming region can be i-type or substantially i-type, and the regions 230ba and 230bb functioning as a source region or a drain region can be n-type. A semiconductor device having electrical characteristics can be provided. Further, with the above structure, even if the semiconductor device is miniaturized or highly integrated, it can have good electrical characteristics. For example, good electrical characteristics can be obtained even if the distance L2 shown in FIG. 11A is 20 nm or less, 15 nm or less, 10 nm or less, or 7 nm or less, and is 2 nm or more, 3 nm or more, or 5 nm or more.

Further, by miniaturizing the transistor 200, high frequency characteristics can be improved. Specifically, the cutoff frequency can be improved. When the gate length is in any of the above ranges, the cutoff frequency of the transistor can be, for example, 50 GHz or higher, or 100 GHz or higher in a room temperature environment.

Insulator 253 functions as part of the gate insulator. As shown in FIG. 9B, the insulator 253 is provided in contact with a portion of the top surface and side surfaces of the insulator 275 and the side surfaces of the insulator 280 .

Insulator 253, along with insulator 254 and conductor 260, must be provided in an opening formed in insulator 280 or the like. In order to miniaturize the transistor 200, the thickness of the insulator 253 is preferably thin. The thickness of the insulator 253 is 0.1 nm or more and 5.0 nm or less, preferably 0.5 nm or more and 5.0 nm or less, more preferably 1.0 nm or more and less than 5.0 nm, further preferably 1.0 nm or more and 3.0 nm or less. Below. In this case, at least part of the insulator 253 may have a region with the thickness as described above.

In order to thin the film thickness of the insulator 253 as described above, it is preferable to form the film using an atomic layer deposition (ALD) method. The ALD method includes a thermal ALD (thermal ALD) method in which a precursor and a reactant react with only thermal energy, a PEALD (plasma enhanced ALD) method using a plasma-excited reactant, and the like. In the PEALD method, film formation can be performed at a lower temperature by using plasma, which is preferable in some cases.

Since the ALD method can deposit atoms one layer at a time, it is possible to form extremely thin films, to form structures with a high aspect ratio, to form films with few defects such as pinholes, and to improve coverage. There are effects such as excellent film formation and low temperature film formation. Therefore, the insulator 253 can be formed with a thin film thickness as described above with good coverage over the side surfaces of the opening formed in the insulator 280 and the like, the side ends of the conductor 242, and the like.

Some precursors used in the ALD method contain carbon and the like. Therefore, a film formed by the ALD method may contain more impurities such as carbon than films formed by other film formation methods. Incidentally, quantification of impurities, secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry), X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy), or Auger electron spectroscopy (AES: Auger Electron Spectroscopy) can be performed using

The insulator 254 functions as part of the gate insulator. The insulator 254 preferably has a barrier property against hydrogen. Accordingly, impurities such as hydrogen contained in the conductor 260 can be prevented from diffusing into the oxide 230b.

In addition, the insulator 254, along with the insulator 253 and the conductor 260, must be provided in an opening formed in the insulator 280 or the like. In order to miniaturize the transistor 200, the thickness of the insulator 254 is preferably thin. The insulator 254 has a thickness of 0.1 nm to 5.0 nm, preferably 0.5 nm to 3.0 nm, more preferably 1.0 nm to 3.0 nm. In this case, at least part of the insulator 254 may have a region with the thickness as described above.

For example, silicon nitride deposited by a PEALD method may be used as the insulator 254 .

Note that when an insulator, such as hafnium oxide, which has a function of suppressing permeation of impurities such as hydrogen and oxygen is used as the insulator 253 , the insulator 253 can also function as the insulator 254 . In such a case, the structure without the insulator 254 can simplify the manufacturing process of the semiconductor device and improve productivity.

An insulator 275 is provided to cover the insulator 224 , the oxides 230 a and 230 b , and the conductor 242 . Specifically, the insulator 275 has regions in contact with the side surfaces of the oxide 230b, the conductor 242a, and the conductor 242b.

Also, the insulator 275 overlaps with the conductor 242 in the opening 258 . With this structure, the physical distance between the conductor 242 and the conductor 260 can be increased, and the parasitic capacitance between the conductor 242 and the conductor 260 can be reduced. Therefore, a semiconductor device having good electrical characteristics can be provided.

As the conductors 242a, 242b, and 260, a conductive material that is difficult to oxidize, a conductive material that has a function of suppressing diffusion (or permeation) of oxygen, or the like is preferably used. Examples of the conductive material include a conductive material containing nitrogen and a conductive material containing oxygen. Accordingly, a decrease in the conductivity of the conductors 242a, 242b, and 260 can be suppressed. When a conductive material containing metal and nitrogen is used for the conductors 242a, 242b, and 260, the conductors 242a, 242b, and 260 are conductive materials containing at least metal and nitrogen. become a body.

One or both of conductor 242 and conductor 260 may have a laminated structure. For example, as shown in FIG. 9B, each of the conductors 242a and 242b may have a two-layer laminated structure. In this case, a conductive material that is difficult to oxidize, a conductive material that has a function of suppressing the diffusion (or permeation) of oxygen, or the like is preferably used for the layers (the conductors 242a1 and 242b1) in contact with the oxide 230b. . Further, for example, as shown in FIG. 9B, when the conductor 260 has a laminated structure of a conductor 260a and a conductor 260b, the conductor 260a is made of a conductive material that is difficult to oxidize or has a function of suppressing the diffusion of oxygen. It is preferable to use a conductive material having

Further, in order to suppress a decrease in conductivity of the conductor 242, a crystalline oxide such as CAAC-OS is preferably used as the oxide 230b. As the oxide, a metal oxide that can be applied to the oxide 230 described above is preferably used. In particular, it is preferable to use a metal oxide containing indium, zinc, and one or more selected from gallium, aluminum, and tin. CAAC-OS is an oxide having crystals, and the c-axis of the crystals is substantially perpendicular to the surface of the oxide or the formation surface. Accordingly, gettering of oxygen from the oxide 230b by the conductor 242a or the conductor 242b can be suppressed. In addition, it is possible to suppress the decrease in conductivity of the conductors 242a and 242b.

In this embodiment, microwave treatment is performed in an oxygen-containing atmosphere with the conductors 242a and 242b covered with the insulator 275 over the oxide 230b and the oxide 230bc exposed. to reduce oxygen vacancies in the region 230bc and _VOH . Here, the microwave treatment refers to treatment using an apparatus having a power supply for generating high-density plasma generated using high frequency waves such as microwaves or RF.

By performing microwave treatment on the sample in the above state in an atmosphere containing oxygen, the generated oxygen plasma can act on the sample. At this time, the region 230bc is also irradiated with microwaves or high frequencies such as RF. By the action of high frequency such as oxygen plasma, microwaves, or RF, _VOH in the region 230bc can be divided into oxygen vacancies and hydrogen, the hydrogen can be removed from the region 230bc, and the oxygen vacancies can be compensated with oxygen. can. Therefore, the hydrogen concentration, oxygen vacancies, and _VOH in the region 230bc are reduced, and the carrier concentration in the region 230bc can be lowered.

Further, when microwave treatment is performed in an atmosphere containing oxygen, microwaves or high frequencies such as RF are shielded by the conductors 242a and 242b. Thus, microwaves or high frequencies such as RF do not affect regions 230ba and 230bb. In addition, since the insulator 275 covering the conductor 242 is provided, oxidation of the conductor 242 by oxygen plasma can be prevented. In addition, since the insulator 275 and the conductor 242 are provided on the regions 230ba and 230bb, even if the microwave treatment is performed in an oxygen-containing atmosphere, the regions 230ba and 230bb have reduced and excessive _VOH . Since a large amount of oxygen is not supplied, it is possible to prevent a decrease in carrier concentration in the regions 230ba and 230bb.

Further, after the insulating film to be the insulator 253 is formed, microwave treatment is preferably performed in an atmosphere containing oxygen. By performing microwave treatment in an atmosphere containing oxygen through the insulator 253 in this manner, oxygen can be efficiently injected into the region 230bc. In addition, by arranging the insulator 253 so as to be in contact with the side surface of the conductor 242 and the surface of the region 230bc, it is possible to suppress the injection of more than a necessary amount of oxygen into the region 230bc and suppress the oxidation of the side surface of the conductor 242. .

The oxygen injected into the region 230bc has various forms such as oxygen atoms, oxygen molecules, and oxygen radicals (also called O radicals, atoms or molecules with unpaired electrons, or ions). Note that the oxygen injected into the region 230bc may be one or more of the forms described above, and oxygen radicals are particularly preferable. In addition, since the film quality of the insulator 253 can be improved, the reliability of the transistor 200 is improved.

In this manner, oxygen vacancies and V _OH can be selectively removed from the oxide semiconductor region 230bc to make the region 230bc i-type or substantially i-type. Furthermore, excessive supply of oxygen to the regions 230ba and 230bb functioning as the source region or the drain region can be suppressed, and the state of the n-type region before the microwave treatment can be maintained. As a result, variations in the electrical characteristics of the transistor 200 can be suppressed, and variations in the electrical characteristics of the transistor 200 within the substrate surface can be suppressed.

With the above structure, a semiconductor device with little variation in transistor characteristics can be provided. In addition, a semiconductor device with favorable frequency characteristics can be provided. In addition, a semiconductor device with high operating speed can be provided. Moreover, a highly reliable semiconductor device can be provided. Moreover, a semiconductor device having favorable electrical characteristics can be provided. Further, a semiconductor device that can be miniaturized or highly integrated can be provided.

As shown in FIG. 9C, in a cross-sectional view of the transistor 200 in the channel width direction, a curved surface may be provided between the side surface of the oxide 230b and the top surface of the oxide 230b. That is, the end of the side surface and the end of the upper surface may be curved (hereinafter also referred to as round shape).

Preferably, the radius of curvature of the curved surface is greater than 0 nm and less than the film thickness of the oxide 230b in the region overlapping the conductor 242, or less than half the length of the region without the curved surface. Specifically, the radius of curvature of the curved surface is greater than 0 nm and less than or equal to 20 nm, preferably greater than or equal to 1 nm and less than or equal to 15 nm, and more preferably greater than or equal to 2 nm and less than or equal to 10 nm. With such a shape, coverage of the oxide 230b with the insulator 253, the insulator 254, and the conductor 260 can be improved.

Further, heat treatment is preferably performed with the surface of the oxide 230 exposed during the manufacturing process of the transistor 200 . The heat treatment may be performed at, for example, 100° C. to 600° C., more preferably 350° C. to 550° C. Note that the heat treatment is performed in a nitrogen gas atmosphere, an inert gas atmosphere, or an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas. For example, heat treatment is preferably performed in an oxygen atmosphere. Accordingly, oxygen can be supplied to the oxide 230 to reduce oxygen vacancies. Moreover, you may perform heat processing in a pressure-reduced state. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas in order to compensate for desorbed oxygen after the heat treatment is performed in a nitrogen gas or inert gas atmosphere. good. Alternatively, after heat treatment in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas, heat treatment may be continuously performed in a nitrogen gas or inert gas atmosphere.

Note that when the oxide 230 is subjected to oxygenation treatment, oxygen vacancies in the oxide 230 can be repaired with supplied oxygen. Furthermore, the supplied oxygen reacts with the hydrogen remaining in the oxide 230, so that the hydrogen can be removed as H ₂ O (dehydrated). This can suppress recombination of hydrogen remaining in the oxide 230 with oxygen vacancies to form _VOH .

In addition, as shown in FIG. 9C and the like, by providing the insulator 253 in contact with the top surface and the side surface of the oxide 230, the indium contained in the oxide 230 and the vicinity of the interface between the oxide 230 and the insulator 253 are dispersed. may be unevenly distributed. As a result, the vicinity of the surface of the oxide 230 has an atomic ratio close to that of indium oxide or an atomic ratio close to that of In—Zn oxide. By increasing the atomic ratio of indium in the vicinity of the surface of the oxide 230, particularly the oxide 230b, the field-effect mobility of the transistor 200 can be improved.

Further, in this embodiment, in addition to the above structure, the semiconductor device preferably has a structure in which entry of hydrogen into the transistor 200 is suppressed. For example, an insulator having a function of suppressing diffusion of hydrogen is preferably provided so as to cover the transistor 200 . In the semiconductor device described in this embodiment, the insulator is the insulator 212, for example.

An insulator having a function of suppressing diffusion of hydrogen is preferably used as the insulator 212 . Accordingly, diffusion of hydrogen into the transistor 200 from below the insulator 212 can be suppressed. Note that an insulator that can be used for the insulator 275 described above may be used as the insulator 212 .

At least one of the insulator 212, the insulator 214, the insulator 282, and the insulator 285 is a barrier that prevents impurities such as water and hydrogen from diffusing from the substrate side or from above the transistor 200 into the transistor 200. It preferably functions as an insulating film. Therefore, at least one of the insulators 212, 214, 282, and 285 includes hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, and nitrogen oxide molecules (N ₂ O, NO, NO ₂ etc.), it is preferable to use an insulating material that has a function of suppressing the diffusion of impurities such as copper atoms (that is, the above-described impurities are less likely to permeate). Alternatively, it is preferable to use an insulating material that has a function of suppressing diffusion of oxygen (for example, at least one of oxygen atoms and oxygen molecules) (through which oxygen hardly permeates).

As the insulator 212, the insulator 214, the insulator 282, and the insulator 285, an insulator having a function of suppressing diffusion of water, impurities such as hydrogen, and oxygen is preferably used; Magnesium, hafnium oxide, gallium oxide, indium gallium zinc oxide, silicon nitride, silicon nitride oxide, or the like can be used. For example, the insulator 212 is preferably made of silicon nitride or the like, which has a higher hydrogen barrier property. Further, for example, the insulators 214, 282, and 285 are preferably made of aluminum oxide, magnesium oxide, or the like, which have high functions of capturing and fixing hydrogen. Thus, impurities such as water and hydrogen can be prevented from diffusing from the substrate side to the transistor 200 side through the insulators 212 and 214 . Alternatively, impurities such as water and hydrogen can be prevented from diffusing toward the transistor 200 from an interlayer insulating film or the like arranged outside the insulator 285 . Alternatively, diffusion of oxygen contained in the insulator 224 or the like to the substrate side through the insulators 212 and 214 can be suppressed. Alternatively, oxygen contained in the insulator 280 or the like can be prevented from diffusing upward from the transistor 200 through the insulator 282 or the like. In this manner, the transistor 200 is preferably surrounded by the insulators 212, 214, 282, and 285 which have a function of suppressing diffusion of water, impurities such as hydrogen, and oxygen.

Here, an oxide having an amorphous structure is preferably used for the insulators 212, 214, 282, and 285. In FIG. For example, it is preferable to use metal oxides such as AlO _x (x is any number greater than 0) or MgO _y (y is any number greater than 0). Oxygen atoms in metal oxides having such an amorphous structure have dangling bonds, and the dangling bonds sometimes have the property of capturing or fixing hydrogen. When such a metal oxide having an amorphous structure is used as a component of the transistor 200 or provided around the transistor 200, hydrogen contained in the transistor 200 or hydrogen existing around the transistor 200 is captured or fixed. be able to. In particular, it is preferable to capture or fix hydrogen contained in the channel formation region of the transistor 200 . By using a metal oxide having an amorphous structure as a component of the transistor 200 or providing it around the transistor 200, the transistor 200 and the semiconductor device with favorable characteristics and high reliability can be manufactured.

Further, although the insulators 212, 214, 282, and 285 preferably have an amorphous structure, they may partially have a polycrystalline region. Alternatively, the insulator 212, the insulator 214, the insulator 282, and the insulator 285 may have a multilayer structure in which an amorphous layer and a polycrystalline layer are stacked. For example, a laminated structure in which a layer of polycrystalline structure is formed on a layer of amorphous structure may be used.

The insulators 212, 214, 282, and 285 may be deposited by a sputtering method, for example. Since the sputtering method does not require molecules containing hydrogen in the deposition gas, the hydrogen concentrations of the insulators 212, 214, 282, and 285 can be reduced. In addition, the film formation method is not limited to the sputtering method, chemical vapor deposition (CVD) method, molecular beam epitaxy (MBE) method, pulsed laser deposition (PLD) method. ) method, ALD method, or the like may be used as appropriate.

Also, it may be preferable to lower the resistivity of the insulator 212 . For example, by setting the resistivity of the insulator 212 to approximately 1×10 ¹³ Ωcm, the insulator 212 can be used as the conductor 205, the conductor 242, the conductor 260, or the Charge-up of the conductor 240 can be alleviated in some cases. The insulator 212 preferably has a resistivity of 1×10 ¹⁰ Ωcm or more and 1×10 ¹⁵ Ωcm or less.

Insulator 216 , insulator 280 , and insulator 285 preferably have lower dielectric constants than insulator 214 . By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance generated between wirings can be reduced. For example, the insulator 216, the insulator 280, and the insulator 285 include silicon oxide, silicon oxynitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and vacancies. Silicon oxide or the like may be used as appropriate.

Conductor 205 is positioned to overlap oxide 230 and conductor 260 . Here, the conductor 205 is preferably embedded in an opening formed in the insulator 216 . Also, part of the conductor 205 is embedded in the insulator 214 in some cases.

The conductor 205 has a conductor 205a and a conductor 205b. The conductor 205a is provided in contact with the bottom and side walls of the opening. The conductor 205b is provided so as to be embedded in a recess formed in the conductor 205a. Here, the height of the top surface of the conductor 205b approximately matches the height of the top surface of the conductor 205a and the height of the top surface of the insulator 216 .

Here, the conductor 205a has a function of suppressing diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (such as N ₂ O, NO, NO ₂ ), and copper atoms. It is preferable to use a conductive material having a Alternatively, a conductive material having a function of suppressing diffusion of oxygen (eg, at least one of oxygen atoms and oxygen molecules) is preferably used.

When a conductive material having a function of reducing diffusion of hydrogen is used for the conductor 205a, impurities such as hydrogen contained in the conductor 205b enter the oxide 230 through the insulators 216, 224, and the like. You can prevent it from spreading. In addition, by using a conductive material having a function of suppressing diffusion of oxygen for the conductor 205a, it is possible to suppress a decrease in conductivity due to oxidation of the conductor 205b. As the conductive material having a function of suppressing diffusion of oxygen, titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like is preferably used, for example. Therefore, the conductor 205a may be a single layer or a laminate of the above conductive materials. For example, the conductor 205a may be titanium nitride.

A conductive material containing tungsten, copper, or aluminum as its main component is preferably used for the conductor 205b. For example, tungsten may be used for the conductor 205b.

Conductor 205 may function as a second gate electrode. In that case, the threshold voltage (Vth) of the transistor 200 can be controlled by changing the potential applied to the conductor 205 independently of the potential applied to the conductor 260 . In particular, by applying a negative potential to the conductor 205, Vth of the transistor 200 can be increased and off-state current can be reduced. Therefore, applying a negative potential to the conductor 205 can make the drain current smaller when the potential applied to the conductor 260 is 0 V than when no potential is applied.

The electric resistivity of the conductor 205 is designed in consideration of the potential applied to the conductor 205, and the film thickness of the conductor 205 is set according to the electric resistivity. Also, the thickness of the insulator 216 is almost the same as that of the conductor 205 . Here, it is preferable to reduce the film thickness of the conductor 205 and the insulator 216 within the range allowed by the design of the conductor 205 . By reducing the thickness of the insulator 216, the absolute amount of impurities such as hydrogen contained in the insulator 216 can be reduced, so that diffusion of the impurities into the oxide 230 can be reduced. .

Note that the conductor 205 is preferably provided larger than a region of the oxide 230 that does not overlap with the conductors 242a and 242b, as shown in FIG. 9A. In particular, as shown in FIG. 9C, the conductor 205 preferably extends also in regions outside the ends of the oxides 230a and 230b in the channel width direction. In other words, the conductor 205 and the conductor 260 preferably overlap with each other with an insulator interposed therebetween on the outside of the side surface of the oxide 230 in the channel width direction. With this structure, the electric field of the conductor 260 functioning as the first gate electrode and the electric field of the conductor 205 functioning as the second gate electrode electrically surround the channel formation region of the oxide 230 . can be done.

In this specification and the like, a transistor structure in which a channel formation region is electrically surrounded by an electric field of at least a first gate electrode is referred to as a surrounded channel (S-channel) structure. Also, the S-channel structure disclosed in this specification and the like has a structure different from the Fin type structure and the planar type structure. On the other hand, the S-channel structure disclosed in this specification etc. can also be regarded as a type of Fin structure. In this specification and the like, a Fin structure indicates a structure in which a gate electrode is arranged so as to cover at least two sides (specifically, two sides, three sides, four sides, etc.) of a channel. By adopting the Fin structure and the S-channel structure, the transistor can have increased resistance to the short channel effect, in other words, a transistor in which the short channel effect is less likely to occur.

When the transistor 200 has the S-channel structure, the channel formation region can be electrically surrounded. Since the S-channel structure is a structure that electrically surrounds the channel forming region, it is substantially equivalent to a GAA (Gate All Around) structure or a LGAA (Lateral Gate All Around) structure. It can also be said. With the transistor 200 having an S-channel structure, a GAA structure, or an LGAA structure, a channel formation region formed at or near the interface between the oxide 230 and the gate insulator is the entire bulk of the oxide 230. can be done. Therefore, since the density of the current flowing through the transistor can be increased, it can be expected that the on-state current of the transistor or the field-effect mobility of the transistor can be increased.

Note that although the transistor 200 illustrated in FIG. 9B has an S-channel structure, the semiconductor device of one embodiment of the present invention is not limited thereto. For example, a transistor structure that can be used in one embodiment of the present invention may be one or more selected from a planar structure, a Fin structure, and a GAA structure.

Further, as shown in FIG. 9C, the conductor 205 is extended to function as wiring. However, without being limited to this, a structure in which a conductor functioning as a wiring is provided under the conductor 205 may be employed. Further, one conductor 205 does not necessarily have to be provided for each transistor. For example, the conductor 205 may be shared by a plurality of transistors.

Note that in the transistor 200, the conductor 205 has a structure in which the conductor 205a and the conductor 205b are stacked; however, the present invention is not limited to this. For example, the conductor 205 may be provided as a single layer or a laminated structure of three or more layers.

Insulator 222 and insulator 224 function as gate insulators.

The insulator 222 preferably has a function of suppressing diffusion of hydrogen (eg, at least one of hydrogen atoms and hydrogen molecules). Further, the insulator 222 preferably has a function of suppressing diffusion of oxygen (eg, at least one of oxygen atoms and oxygen molecules). For example, the insulator 222 preferably has a function of suppressing diffusion of one or both of hydrogen and oxygen more than the insulator 224 does.

The insulator 222 preferably contains an oxide of one or both of aluminum and hafnium, which are insulating materials. As the insulator, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used. Alternatively, it is preferable to use an oxide containing hafnium and zirconium, such as hafnium zirconium oxide. When the insulator 222 is formed using such a material, the insulator 222 releases oxygen from the oxide 230 to the substrate side and diffuses impurities such as hydrogen from the peripheral portion of the transistor 200 to the oxide 230. It functions as a layer that suppresses Therefore, by providing the insulator 222, diffusion of impurities such as hydrogen into the transistor 200 can be suppressed, and generation of oxygen vacancies in the oxide 230 can be suppressed. In addition, the conductor 205 can be prevented from reacting with oxygen contained in the insulator 224 and the oxide 230 .

Alternatively, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to the insulator. Alternatively, these insulators may be nitrided. Alternatively, the insulator 222 may be formed by stacking silicon oxide, silicon oxynitride, or silicon nitride on the above insulator.

Alternatively, the insulator 222 may be a single layer or a stack of insulators containing so-called high-k materials such as aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, and hafnium zirconium oxide. As transistors are miniaturized and highly integrated, thinning of gate insulators may cause problems such as leakage current. By using a high-k material for an insulator that functions as a gate insulator, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness. Also, as the insulator 222, a substance with a high dielectric constant such as lead zirconate titanate (PZT), strontium titanate (SrTiO ₃ ), (Ba, Sr)TiO ₃ (BST) may be used in some cases.

For the insulator 224 in contact with the oxide 230, for example, silicon oxide, silicon oxynitride, or the like may be used as appropriate.

Note that the insulator 222 and the insulator 224 may have a stacked structure of two or more layers. In that case, the layered structure is not limited to a layered structure containing the same material, and may be a layered structure containing different materials. Alternatively, the insulator 224 may be formed in an island shape so as to overlap with the oxide 230a. In this case, the insulator 275 is in contact with the side surface of the insulator 224 and the top surface of the insulator 222 . Note that, in this specification and the like, an island shape indicates a state in which two or more layers using the same material formed in the same step are physically separated.

Conductors 242a and 242b are provided in contact with the top surface of oxide 230b. The conductors 242a and 242b function as the source and drain electrodes of the transistor 200, respectively.

Examples of the conductor 242 (the conductor 242a and the conductor 242b) include nitride containing tantalum, nitride containing titanium, nitride containing molybdenum, nitride containing tungsten, nitride containing tantalum and aluminum, and titanium. and a nitride containing aluminum is preferably used. In one aspect of the present invention, nitrides containing tantalum are particularly preferred. Alternatively, for example, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, or the like may be used. These materials are preferable because they are conductive materials that are difficult to oxidize or materials that maintain conductivity even after absorbing oxygen.

Note that hydrogen contained in the oxide 230b or the like might diffuse into the conductor 242a or the conductor 242b. In particular, when a nitride containing tantalum is used for the conductors 242a and 242b, hydrogen contained in the oxide 230b or the like easily diffuses into the conductor 242a or the conductor 242b, and the diffused hydrogen 242a or the conductor 242b. That is, hydrogen contained in the oxide 230b or the like might be absorbed by the conductor 242a or the conductor 242b.

Moreover, it is preferable that no curved surface is formed between the side surface of the conductor 242 and the upper surface of the conductor 242 . By using the conductor 242 without the curved surface, the cross-sectional area of the conductor 242 in the cross section in the channel width direction as shown in FIG. 9D can be increased. Accordingly, the conductivity of the conductor 242 can be increased, and the on current of the transistor 200 can be increased.

Also, as shown in FIG. 9A, the conductor 242a has an opening in the region between the transistor 200a and the transistor 200b. A conductor 240 is arranged so as to overlap with the opening. With such a structure, the conductor 242a and the conductor 240 have a contact region. Thereby, the conductor 242a and the conductor 240 are electrically connected.

Further, when heat treatment is performed while the conductor 242a (the conductor 242b) and the oxide 230b are in contact with each other, the sheet resistance of the oxide 230b in a region overlapping with the conductor 242a (the conductor 242b) is reduced. Sometimes. Also, the carrier concentration may increase. Therefore, the resistance of the oxide 230b in the region overlapping with the conductor 242a (the conductor 242b) can be reduced in a self-aligning manner.

The conductors 242a and 242b are preferably formed using a conductive film having compressive stress. As a result, a strain expanding in the direction of tension (hereinafter sometimes referred to as tensile strain) can be formed in the regions 230ba and 230bb. By stably forming _VOH by tensile strain, the regions 230ba and 230bb can be made into stable n-type regions. The compressive stress of the conductor 242a is the stress that tends to relax the compressed shape of the conductor 242a, and is the stress that has a vector in the direction from the center to the end of the conductor 242a. The same applies to the compressive stress of the conductor 242b.

The magnitude of the compressive stress of the conductor 242a is, for example, 500 MPa or more, preferably 1000 MPa or more, more preferably 1500 MPa or more, and still more preferably 2000 MPa or more. Note that the magnitude of the stress of the conductor 242a may be determined by measuring the stress of a sample obtained by forming a conductive film used for the conductor 242a over a substrate. The same applies to the magnitude of the compressive stress that the conductor 242b has. Nitride containing tantalum is an example of a conductor having the magnitude of compressive stress described above.

Strains are formed in the regions 230ba and 230bb by the action of the compressive stresses of the conductors 242a and 242b. The strain is a strain (tensile strain) expanded in the direction of tension by the action of the compressive stress of the conductors 242a and 242b. When regions 230ba and 230bb have a CAAC structure, the strain corresponds to stretching of the CAAC structure in a direction perpendicular to the c-axis. As the CAAC structure extends in the direction perpendicular to the c-axis of the CAAC structure, oxygen vacancies are likely to be formed in the strain. In addition, since hydrogen is likely to be incorporated into the strain, _VOH is likely to be formed. Therefore, in the strain, oxygen vacancies and _VOH are likely to be formed, and these tend to have a stable structure. As a result, the regions 230ba and 230bb become stable n-type regions with high carrier concentrations.

Although the strain formed in the oxide 230b has been described above, the present invention is not limited to this. A similar strain may form in oxide 230a.

In the semiconductor devices shown in FIGS. 9A to 9D, the conductor 242 has a two-layer structure. Specifically, the conductor 242a has a conductor 242a1 and a conductor 242a2 on the conductor 242a1. Similarly, conductor 242b has conductor 242b1 and conductor 242b2 above conductor 242b1. At this time, the conductor 242a1 and the conductor 242b1 are arranged on the side in contact with the oxide 230b.

Note that the conductor 242a1 and the conductor 242b1 may be collectively referred to as a lower layer of the conductor 242 below. Further, the conductor 242a2 and the conductor 242b2 may be collectively referred to as an upper layer of the conductor 242 in some cases.

The lower layers of the conductor 242 (the conductor 242a1 and the conductor 242b1) are preferably made of a conductive material that is resistant to oxidation. Accordingly, it is possible to prevent the lower layer of the conductor 242 from being oxidized and the conductivity of the conductor 242 from decreasing. Note that the lower layer of the conductor 242 may have a property of easily absorbing (releasing) hydrogen. As a result, hydrogen in the oxide 230 diffuses into the lower layer of the conductor 242, so that the hydrogen concentration in the oxide 230 can be reduced. Therefore, the transistor 200 can have stable electrical characteristics. In addition, the lower layer of the conductor 242 preferably has a large compressive stress as described above, and preferably has a larger compressive stress than the upper layer of the conductor 242 . Thereby, as described above, the regions 230ba and 230bb in contact with the lower layer of the conductor 242 can be made stable n-type regions with high carrier concentration.

Moreover, the upper layers of the conductor 242 (the conductor 242a2 and the conductor 242b2) preferably have higher conductivity than the lower layers of the conductor 242 (the conductor 242a1 and the conductor 242b1). For example, the thickness of the upper layer of the conductor 242 may be larger than the thickness of the lower layer of the conductor 242 . Note that at least part of the upper layer of the conductor 242 may have a region with higher conductivity than the lower layer of the conductor 242 . Alternatively, the upper layer of the conductor 242 is preferably made of a conductive material with a lower resistivity than the lower layer of the conductor 242 . Thereby, a semiconductor device in which wiring delay is suppressed can be manufactured.

Note that the upper layer of the conductor 242 may have a characteristic of easily absorbing hydrogen. As a result, hydrogen absorbed in the lower layer of the conductor 242 diffuses into the upper layer of the conductor 242, so that the hydrogen concentration in the oxide 230 can be further reduced. Therefore, the transistor 200 can have stable electrical characteristics.

When the conductor 242 has a two-layer laminated structure, one or more selected from constituent elements, chemical compositions, and film formation conditions may be different for the lower layer of the conductor 242 and the upper layer of the conductor 242. .

For example, tantalum nitride or titanium nitride can be used as the lower layers of the conductors 242 (the conductors 242a1 and 242b1), and tungsten can be used as the upper layers of the conductors 242 (the conductors 242a2 and 242b2). In this case, the conductor 242a1 and the conductor 242b1 are conductors containing tantalum or titanium and nitrogen. With such a structure, oxidation of the lower layer of the conductor 242 and reduction in conductivity of the conductor 242 can be suppressed. In addition, with this structure, the conductor 242a2 is surrounded by the insulator 275 having a barrier property against oxygen and the conductor 242a1 having a property that is not easily oxidized, and the insulator 275 having a barrier property against oxygen surrounds the conductor 242b2. , and a conductor 242b1 that is resistant to oxidation. Therefore, it is possible to manufacture a semiconductor device in which oxidation of the conductors 242a2 and 242b2 is suppressed and wiring delay is suppressed.

Alternatively, for example, a nitride containing tantalum (eg, tantalum nitride) may be used as the lower layer of the conductor 242 and a nitride containing titanium (eg, titanium nitride) may be used as the upper layer of the conductor 242 . Since titanium nitride can be more conductive than tantalum nitride, the top layer of conductor 242 can be more conductive than the bottom layer of conductor 242 . Therefore, since the contact resistance with the conductor 240 provided in contact with the top surface of the conductor 242 can be reduced, a semiconductor device in which wiring delay is suppressed can be manufactured.

Although the lower layer of the conductor 242 and the upper layer of the conductor 242 use different conductive materials, the present invention is not limited to this.

The lower layer of the conductor 242 and the upper layer of the conductor 242 may be made of conductive materials having the same constituent elements and different chemical compositions. At this time, the lower layer of the conductor 242 and the upper layer of the conductor 242 can be continuously formed without being exposed to the atmospheric environment. By forming the film without exposure to the atmosphere, impurities or moisture from the atmospheric environment can be prevented from adhering to the surface of the lower layer of the conductor 242, and the vicinity of the interface between the lower layer and the upper layer of the conductor 242 can be prevented. can be kept clean.

In addition, a nitride containing tantalum with a high nitrogen to tantalum atomic ratio is used for the lower layer of the conductor 242 , and a tantalum containing nitride with a low nitrogen to tantalum atomic ratio is used for the upper layer of the conductor 242 . It is preferable to use For example, as the lower layer of the conductor 242, tantalum with an atomic ratio of nitrogen to tantalum of 1.0 to 2.0, preferably 1.1 to 1.8, more preferably 1.2 to 1.5 Use a nitride containing Further, for example, the upper layer of the conductor 242 has an atomic ratio of nitrogen to tantalum of 0.3 to 1.5, preferably 0.5 to 1.3, more preferably 0.6 to 1.0. of tantalum-containing nitride is used.

By increasing the atomic ratio of nitrogen to tantalum in the nitride containing tantalum, oxidation of the nitride containing tantalum can be suppressed. In addition, the oxidation resistance of the nitride containing tantalum can be enhanced. In addition, diffusion of oxygen into the nitride containing tantalum can be suppressed. Therefore, it is preferable to use a nitride containing tantalum, which has a high atomic ratio of nitrogen to tantalum, for the lower layer of the conductor 242 . This can prevent the formation of an oxide layer between the lower layer of the conductor 242 and the oxide 230 or reduce the thickness of the oxide layer.

In addition, in a nitride containing tantalum, by lowering the atomic ratio of nitrogen to tantalum, the resistivity of the nitride can be lowered. Therefore, it is preferable to use a nitride containing tantalum, which has a low atomic ratio of nitrogen to tantalum, for the top layer of the conductor 242 . Accordingly, a semiconductor device in which wiring delay is suppressed can be manufactured.

Note that it may be difficult to clearly detect the boundary between the upper layer and the lower layer in the conductor 242 . When a nitride containing tantalum is used for the conductor 242, the concentrations of tantalum and nitrogen detected in each layer are not limited to stepwise changes in each layer, but are continuously changed in the region between the upper layer and the lower layer ( (also called gradation). That is, the closer the region of the conductor 242 to the oxide 230, the higher the atomic ratio of nitrogen to tantalum. Therefore, the atomic ratio of nitrogen to tantalum in the region below conductor 242 is preferably higher than the atomic ratio of nitrogen to tantalum in the region above conductor 242 .

Note that although the transistor 200 shows the structure in which the conductor 242 is stacked in two layers, the present invention is not limited to this. For example, the conductor 242 may be provided as a single layer or a laminated structure of three or more layers. When the structure has a laminated structure, an ordinal number may be assigned in order of formation for distinction.

Conductor 260 is positioned such that its top surface is approximately level with the top of insulator 254 , the top of insulator 253 , and the top of insulator 280 .

Conductor 260 functions as a first gate electrode of transistor 200 . The conductor 260 preferably has a conductor 260a and a conductor 260b disposed over the conductor 260a. For example, conductor 260a is preferably arranged to wrap the bottom and side surfaces of conductor 260b. In FIGS. 9B and 9C, the conductor 260 has a two-layer structure of conductors 260a and 260b, but may have a single-layer structure or a laminated structure of three or more layers.

For the conductor 260a, a conductive material having a function of suppressing diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules, and copper atoms is preferably used. Alternatively, a conductive material having a function of suppressing diffusion of oxygen (eg, at least one of oxygen atoms and oxygen molecules) is preferably used.

In addition, since the conductor 260a has a function of suppressing the diffusion of oxygen, it is possible to prevent the conductor 260b from being oxidized by oxygen diffused from the insulator 280 and reducing the conductivity. As the conductive material having a function of suppressing diffusion of oxygen, titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like is preferably used, for example.

Further, the conductor 260 is formed so as to fill the opening 258 provided extending in the channel width direction, and the conductor 260 is also provided extending in the channel width direction. Accordingly, when a plurality of transistors 200 are provided, the conductor 260 can also function as a wiring. In this case, the insulator 253 and the insulator 254 are also provided to extend along with the conductor 260 .

In addition, since the conductor 260 also functions as a wiring, a conductor with high conductivity is preferably used. For example, the conductor 260b can use a conductive material whose main component is tungsten, copper, or aluminum. Further, the conductor 260b may have a layered structure, for example, a layered structure of titanium or titanium nitride and any of the above conductive materials.

Further, in the transistor 200, the conductor 260 is formed in a self-aligned manner so as to fill the opening 258 formed in the insulator 280 or the like. By forming the conductor 260 in this manner, the conductor 260 can be reliably placed in the region between the conductors 242a and 242b without being aligned.

In addition, as shown in FIG. 9C, the height of the bottom surface of the region of the conductor 260 where the conductor 260 and the oxide 230b do not overlap with each other is based on the bottom surface of the insulator 222 in the channel width direction of the transistor 200. The height is preferably less than the height of the bottom surface of oxide 230b. The conductor 260 functioning as a gate electrode covers the side surface and top surface of the channel formation region of the oxide 230b with the insulator 253 or the like interposed therebetween. Easier to work on the whole. Therefore, the on current of the transistor 200 can be increased and the frequency characteristics can be improved. With respect to the bottom surface of the insulator 222, the height of the bottom surface of the conductor 260 and the height of the bottom surface of the oxide 230b in a region where the oxides 230a and 230b do not overlap with the conductor 260. The difference is 0 nm or more and 100 nm or less, preferably 3 nm or more and 50 nm or less, more preferably 5 nm or more and 20 nm or less.

The insulator 280 is provided over the insulator 275, and openings are formed in regions where the insulator 253, the insulator 254, and the conductor 260 are provided. Also, the upper surface of the insulator 280 may be flattened.

The insulator 280 functioning as an interlayer film preferably has a low dielectric constant. By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance generated between wirings can be reduced. The insulator 280 is preferably provided using a material similar to that of the insulator 216, for example. In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In particular, a material such as silicon oxide, silicon oxynitride, or silicon oxide having vacancies is preferable because a region containing oxygen released by heating can be easily formed.

The insulator 280 preferably has a reduced concentration of impurities such as water and hydrogen. For example, an oxide containing silicon such as silicon oxide or silicon oxynitride may be used as appropriate for the insulator 280 .

Insulator 282 is arranged to be in contact with at least part of the upper surface of each of conductor 260 , insulator 253 , insulator 254 , and insulator 280 .

The insulator 282 preferably functions as a barrier insulating film that prevents impurities such as water and hydrogen from diffusing into the insulator 280 from above, and preferably has a function of capturing impurities such as hydrogen. Further, the insulator 282 preferably functions as a barrier insulating film that suppresses permeation of oxygen. As the insulator 282, an insulator such as a metal oxide having an amorphous structure such as aluminum oxide may be used. In this case, the insulator 282 is an insulator containing at least oxygen and aluminum. By providing the insulator 282 having a function of capturing impurities such as hydrogen in contact with the insulator 280, impurities such as hydrogen contained in the insulator 280 and the like can be captured. In particular, it is preferable to use aluminum oxide having an amorphous structure as the insulator 282 because hydrogen can be trapped or fixed more effectively in some cases. Accordingly, the transistor 200 and the semiconductor device with favorable characteristics and high reliability can be manufactured.

As the insulator 282, aluminum oxide is preferably deposited by a sputtering method, and more preferably by a pulse DC sputtering method using an aluminum target in an atmosphere containing oxygen gas. By using the pulse DC sputtering method, the film thickness distribution can be made more uniform, and the sputtering rate and film quality can be improved. Here, RF (Radio Frequency) power may be applied to the substrate. The amount of oxygen injected into layers below the insulator 282 can be controlled by the amount of RF power applied to the substrate. For example, the smaller the RF power, the smaller the amount of oxygen injected into a layer below the insulator 282, and the oxygen amount is likely to be saturated even if the thickness of the insulator 282 is thin. Also, the amount of oxygen injected into the layer below the insulator 282 increases as the RF power increases.

RF power is, for example, 0 W/cm ² or more and 1.86 W/cm ² or less. In other words, the amount of oxygen suitable for the characteristics of the transistor can be changed and implanted depending on the RF power when the insulator 282 is formed. Therefore, the amount of oxygen suitable for improving the reliability of the transistor can be implanted.

Also, the RF frequency is preferably 10 MHz or higher. It is typically 13.56 MHz. The higher the RF frequency, the smaller the damage to the substrate.

9A to 9D and the like show a structure in which the insulator 282 is a single layer, the present invention is not limited to this, and a laminated structure of two or more layers may be employed. For example, the insulator 282 may have a laminated structure of two layers.

The upper and lower layers of insulator 282 may be formed of the same material by different methods. For example, when an aluminum target is used as the insulator 282 in an atmosphere containing oxygen gas to form an aluminum oxide film by a pulsed DC sputtering method, the RF power applied to the substrate when forming the lower layer of the insulator 282 and the , the RF power applied to the substrate when depositing the upper layer of the insulator 282 is preferably different, and the RF power applied to the substrate when depositing the lower layer of the insulator 282 is different from the RF power applied to the substrate when depositing the upper layer of the insulator 282. It is more preferably lower than the RF power applied to the substrate during film formation. Specifically, the lower layer of the insulator 282 is deposited with RF power applied to the substrate of 0 W/cm ² or more and 0.62 W/cm ² or less, and the RF power of the upper layer of the insulator 282 applied to the substrate is 1.0 W/cm 2 or more. A film is formed at 86 W/cm ² or less. More specifically, the lower layer of the insulator 282 is deposited with an RF power of 0 W/cm ² applied to the substrate, and the upper layer of the insulator 282 is deposited with an RF power of 0.31 W/cm ² applied to the substrate. do. With such a structure, the insulator 282 can have an amorphous structure and the amount of oxygen supplied to the insulator 280 can be adjusted.

Note that the RF power applied to the substrate when forming the lower layer of the insulator 282 may be higher than the RF power applied to the substrate when forming the upper layer of the insulator 282 . Specifically, the lower layer of the insulator 282 is deposited with RF power applied to the substrate of 1.86 W/cm ² or less, and the upper layer of the insulator 282 is deposited with the RF power applied to the substrate of 0 W/cm ² or more. A film is formed at 62 W/cm ² or less. More specifically, the lower layer of the insulator 282 is deposited with an RF power of 1.86 W/cm ² applied to the substrate, and the upper layer of the insulator 282 is deposited with an RF power of 0.62 W/cm ² applied to the substrate. form a film. With such a structure, the amount of oxygen supplied to the insulator 280 can be increased.

The thickness of the lower layer of the insulator 282 is 1 nm to 20 nm, preferably 1.5 nm to 15 nm, more preferably 2 nm to 10 nm, further preferably 3 nm to 8 nm. With this structure, the lower layer of the insulator 282 can have an amorphous structure regardless of RF power. By forming the lower layer of the insulator 282 to have an amorphous structure, the upper layer of the insulator 282 tends to have an amorphous structure, and the insulator 282 can have an amorphous structure.

Although the lower layer of the insulator 282 and the upper layer of the insulator 282 have a laminated structure including the same material, the present invention is not limited to this. The lower layer of insulator 282 and the upper layer of insulator 282 may be laminated structures comprising different materials.

The above is the description of the transistor 200 .

[Capacitor 150]
12A shows an enlarged view of capacitive element 150 and its vicinity in FIG. 9B, and FIG. 12B shows an enlarged view of capacitive element 150 and its vicinity in FIG. 9D.

The capacitor 150 includes a conductor 242b, an insulator 275, an insulator 153, an insulator 154, and a conductor 160 (a conductor 160a and a conductor 160b). The conductor 242b functions as one of a pair of electrodes (also referred to as a lower electrode) of the capacitor 150, the conductor 160 functions as the other of the pair of electrodes (also referred to as an upper electrode) of the capacitor 150, and the insulator 275, The insulator 153 and the insulator 154 function as dielectrics of the capacitor 150 .

Insulator 153 , insulator 154 , conductor 160 a , and conductor 160 b are arranged in opening 158 provided in insulator 280 . The insulator 153 is provided over the insulator 275, the insulator 154 is provided over the insulator 153, the conductor 160a is provided over the insulator 154, and the conductor 160b is provided over the conductor 160a.

Although the details will be described later, the insulator 153, the insulator 154, the conductor 160a, and the conductor 160b that constitute the capacitor 150 correspond to the insulator 253, the insulator 254, the conductor 260a, and the conductor that constitute the transistor 200. It can be formed using the same material and in the same process as the conductor 260b. Therefore, the insulator 153 preferably contains the same insulating material as the insulator 253, and the description of the insulator 253 can be referred to for details. The insulator 154 preferably contains the same insulating material as the insulator 254, and the description of the insulator 254 can be referred to for details. The conductor 160a preferably contains the same conductive material as the conductor 260a, and the description of the conductor 260a can be referred to for details. The conductor 160b preferably contains the same conductive material as the conductor 260b, and the description of the conductor 260b can be referred to for details.

The insulator 153, the insulator 154, the conductor 160a, and the conductor 160b are formed using the same material and in the same process as the insulator 253, the insulator 254, the conductor 260a, and the conductor 260b, respectively, so that the semiconductor device can be manufactured. , the number of steps can be reduced.

Opening 158 is provided in insulator 280 to reach insulator 275 . That is, it can be said that the opening 158 has a region overlapping with the insulator 275 .

As shown in FIG. 9A , in plan view, a region where the conductor 160 in the opening 158 and the conductor 242 b intersect functions as the capacitive element 150 . This region has an overlapping region with oxide 230 b that functions as transistor 200 . In other words, the capacitor 150 can be provided without excessively increasing the area occupied by the transistor 200 . As a result, miniaturization or high integration of the semiconductor device can be achieved. For example, when the semiconductor device according to one embodiment of the present invention is used as a memory cell of a memory device, memory capacity per unit area can be increased.

The conductor 242b can also serve as the lower electrode of the capacitor 150 and the other of the source and drain electrodes of the transistor 200 . Therefore, part of the manufacturing process of the transistor 200 can be used in the manufacturing process of the capacitor 150, so that the semiconductor device can be manufactured with high productivity.

12A, the end of the conductor 242b on the capacitor 150 side is preferably located outside the end of the oxide 230. In addition, as shown in FIG. In other words, the conductor 242b covers the side surface of the oxide 230 on the capacitor 150 side. Since the conductor 242b functions as one of the pair of electrodes of the capacitor 150, the area over which the pair of electrodes of the capacitor 150 overlap can be increased. Therefore, the capacitance value of the capacitive element 150 can be increased.

12A and 12B, the opening 158 includes insulator 224, oxide 230, conductor 242, and insulator 224, oxide 230, conductor 242, and insulator 222 on the bottom and insulator 280 on the sides. It can also be regarded as a shape in which part of the structure including 275 protrudes. Note that the top surface of the oxide 230b is not exposed in the opening 158 because the top surface of the oxide 230b is covered with the conductor 242b and the insulator 275 unlike the opening 258 .

As shown in FIGS. 12A and 12B, insulator 153 is provided in contact with the bottom and inner walls of opening 158 . Therefore, insulator 153 is in contact with the top surface of insulator 275 and the side surface of insulator 280 . An insulator 154 is provided over the insulator 153 in contact with the top surface of the insulator 153 , and a conductor 160 is provided in contact with the top surface of the insulator 154 . Therefore, insulator 153 , insulator 154 and conductor 160 are provided to cover conductor 242 b and insulator 275 partially protruding into opening 158 .

12A and 12B, the upper surface of the conductor 242b and the side surface of the conductor 242b on the side different from the conductor 242a (A1 the A5 side of the conductor 242b, and the A6 side of the conductor 242b. and an insulator 154 are provided to face each other. Accordingly, since the capacitive element 150 can be formed on the four surfaces of the conductor 242b, the capacitance per unit area of the capacitive element 150 can be increased. Therefore, miniaturization or high integration of the semiconductor device can be achieved.

By optimizing the material used for the insulator that functions as a dielectric, the film thickness of the insulator 280, and the like, the capacitive element 150 may have, for example, the shape shown in FIG. 13A. Specifically, a side surface of the opening 158 on a side different from the conductor 242a (a side surface on the A1 side in the capacitor 150a and a side surface on the A2 side in the capacitor 150b) overlaps with the oxide 230b. may In addition, a conductor 160 is provided to face the upper surface of the conductor 242b, the side surface of the conductor 242b on the A5 side, and the side surface of the conductor 242b on the A6 side with the insulators 153 and 154 interposed therebetween. It may be configured to be At this time, the capacitive element 150 can be formed on the three surfaces of the conductor 242b. Alternatively, capacitive element 150 may have, for example, the shape shown in FIG. 13B. Specifically, opening 158 may be provided in a region that does not overlap oxide 230b.

12A, 13A, and 13B show a configuration in which the sidewalls of opening 158 are substantially perpendicular to the top surface of insulator 222, but the invention is not so limited. The sidewalls of opening 158 may be tapered. Although the details will be described later, the opening 258 and the opening 158 are formed in the same process. For example, as shown in FIG. 11C, if the sidewalls of opening 258 are tapered, the sidewalls of opening 158 are also tapered. By tapering the side wall of the opening 158, coverage with the insulator 153 or the like is improved in subsequent steps, and defects such as voids can be reduced.

Further, the conductor 160 is formed to fill an opening 158 extending in the channel width direction of the transistor 200, and the conductor 160 is also provided extending in the channel width direction of the transistor 200. there is Accordingly, when a plurality of transistors 200 and capacitors 150 are provided, the conductor 160 can also function as a wiring. In this case, the insulators 153 and 154 are also provided to extend along with the conductor 160 .

Insulator 275 , insulator 153 , and insulator 154 function as dielectrics of capacitive element 150 . A region of the insulator 153 that functions as the dielectric of the capacitor 150 is sandwiched between the insulator 275 and the insulator 154 .

Also, the region 230bb of the oxide 230b is a low-resistance region. Therefore, region 230bb of oxide 230b may function as the bottom electrode of capacitive element 150 . At this time, the area where the pair of electrodes of the capacitor 150 overlap can be increased. Therefore, the capacitance value of the capacitive element 150 can be increased.

The above is the description of the capacitor 150 .

The conductor 240 is provided in contact with the inner walls of the openings of the insulator 285, the insulator 282, the insulator 280, the insulator 275, the conductor 242a, the insulator 222, the insulator 216, the insulator 214, and the insulator 212. ing. In addition, the conductor 240 has a region in contact with the top surface of the conductor 209 .

The conductor 240 functions as a plug or wiring for electrically connecting circuit elements such as switches, transistors, capacitors, inductors, resistors, and diodes, wirings, electrodes, or terminals to the transistor 200 .

The conductor 240 preferably has a laminated structure of a conductor 240a and a conductor 240b. For example, as shown in FIG. 9B, the conductor 240 can have a structure in which a conductor 240a is provided in contact with the inner wall of the opening, and a conductor 240b is provided inside. That is, the conductor 240 a is arranged near the insulator 285 , the insulator 282 , the insulator 280 , the insulator 275 , the conductor 242 a , the insulator 222 , the insulator 216 , the insulator 214 , and the insulator 212 .

As the conductor 240a, a conductive material having a function of suppressing permeation of impurities such as water and hydrogen is preferably used. For example, it is preferable to use tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, ruthenium oxide, or the like. In addition, the conductive material having a function of suppressing permeation of impurities such as water and hydrogen may be used in a single layer or stacked layers. In addition, impurities such as water and hydrogen contained in layers above the insulator 282 can be prevented from entering the oxide 230 through the conductor 240 .

In addition, since the conductor 240 also functions as a wiring, a conductor with high conductivity is preferably used. For example, the conductor 240b can use a conductive material containing tungsten, copper, or aluminum as its main component.

Note that although the transistor 200 has a structure in which the conductor 240a and the conductor 240b are stacked as the conductor 240, the present invention is not limited to this. For example, the conductor 240 may be provided as a single layer or a laminated structure of three or more layers. When the structure has a laminated structure, an ordinal number may be assigned in order of formation for distinction. Also, although not shown in FIG. 9B, the height of the top surface of the conductor 240 may be higher than the height of the top surface of the insulator 285 .

FIG. 10 shows an enlarged view of a region where the conductor 240 and the conductor 242a are in contact with each other and its vicinity. As shown in FIG. 10, in the A1-A2 direction, conductor 240 has a region with width W1 and a region with width W2. The width W1 corresponds to, for example, the distance between the interface between the insulator 280 and the conductor 240a on the transistor 200a side and the interface between the insulator 280 and the conductor 240a on the transistor 200b side. Also, the width W2 corresponds to the width of the opening of the conductor 242a.

As shown in FIG. 10, width W1 is preferably greater than width W2. In this configuration, the conductor 240 contacts at least part of the top surface and part of the side surface of the conductor 242a. Therefore, the area of the region where the conductor 240 and the conductor 242a are in contact can be increased. Note that in this specification and the like, the contact between the conductor 240 and the conductor 242a is sometimes called a topside contact. Also, as shown in FIG. 10, the conductor 240 may contact a portion of the lower surface of the conductor 242a. With this structure, the area of the region where the conductor 240 and the conductor 242a are in contact can be further increased.

The conductor 209 functions as part of circuit elements such as switches, transistors, capacitors, inductors, resistors, and diodes, wirings, electrodes, or terminals.

Insulator 210 also functions as an interlayer film. As the insulator 210, an insulator that can be used for the insulators 214, 216, or the like may be used.

<Semiconductor Device Constituent Material>
Constituent materials that can be used for the semiconductor device are described below.

<<Substrate>>
As a substrate for forming the transistor 200, an insulator substrate, a semiconductor substrate, or a conductor substrate may be used, for example. Examples of insulator substrates include glass substrates, quartz substrates, sapphire substrates, stabilized zirconia substrates (yttria stabilized zirconia substrates, etc.), and resin substrates. Semiconductor substrates include, for example, semiconductor substrates made of silicon or germanium, or compound semiconductor substrates containing silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, or gallium oxide. Further, there is a semiconductor substrate having an insulator region inside the semiconductor substrate, such as an SOI (Silicon On Insulator) substrate. Examples of conductive substrates include graphite substrates, metal substrates, alloy substrates, and conductive resin substrates. Alternatively, there are a substrate having a metal nitride, a substrate having a metal oxide, and the like. Furthermore, there are substrates in which an insulator substrate is provided with a conductor or a semiconductor, a substrate in which a semiconductor substrate is provided with a conductor or an insulator, a substrate in which a conductor substrate is provided with a semiconductor or an insulator, and the like. Alternatively, these substrates provided with elements may be used. Elements provided on the substrate include a capacitor element, a resistance element, a switch element, a light emitting element, a memory element, and the like.

<<insulator>>
As insulators, there are insulating oxides, nitrides, oxynitrides, nitride oxides, metal oxides, metal oxynitrides, metal nitride oxides, and the like.

For example, as transistors are miniaturized and highly integrated, thinning of gate insulators may cause problems such as leakage current. By using a high-k material for an insulator functioning as a gate insulator, voltage reduction during transistor operation can be achieved while maintaining a physical film thickness. On the other hand, by using a material with a low dielectric constant for the insulator functioning as an interlayer film, parasitic capacitance generated between wirings can be reduced. Therefore, the material should be selected according to the function of the insulator.

Insulators with a high relative dielectric constant include gallium oxide, hafnium oxide, zirconium oxide, oxides containing aluminum and hafnium, oxynitrides containing aluminum and hafnium, oxides containing silicon and hafnium, and silicon and hafnium. oxynitrides with silicon, or nitrides with silicon and hafnium.

Insulators with a low relative dielectric constant include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and an empty silicon oxide. There are silicon oxide with pores, resin, and the like.

In addition, when a transistor including a metal oxide is surrounded by an insulator having a function of suppressing permeation of impurities such as hydrogen and oxygen, electrical characteristics of the transistor can be stabilized. Examples of insulators having a function of suppressing permeation of impurities such as hydrogen and oxygen include boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, and zirconium. Insulators including lanthanum, neodymium, hafnium, or tantalum may be used in single layers or in stacks. Specifically, as insulators having a function of suppressing permeation of impurities such as hydrogen and oxygen, aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, Metal oxides such as tantalum oxide, and metal nitrides such as aluminum nitride, silicon nitride oxide, and silicon nitride can be used.

An insulator that functions as a gate insulator preferably has a region containing oxygen that is released by heating. For example, by forming a structure in which silicon oxide or silicon oxynitride having a region containing oxygen released by heating is in contact with the oxide 230, oxygen vacancies in the oxide 230 can be compensated.

<<Conductor>>
Conductors include aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum. It is preferable to use a metal element selected from among the above, an alloy containing the above-described metal elements as a component, or an alloy or the like in which the above-described metal elements are combined. For example, tantalum nitride, titanium nitride, tungsten, nitride containing titanium and aluminum, nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxide containing strontium and ruthenium, oxide containing lanthanum and nickel, and the like are used. is preferred. Also, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are difficult to oxidize. It is preferable because it is a conductive material or a material that maintains conductivity even after absorbing oxygen. Alternatively, a semiconductor with high electrical conductivity, typified by polycrystalline silicon containing an impurity element such as phosphorus, or a silicide such as nickel silicide may be used.

Alternatively, a plurality of conductive layers formed using any of the above materials may be stacked and used. For example, a laminated structure in which the material containing the metal element described above and the conductive material containing oxygen are combined may be used. Alternatively, a laminated structure may be employed in which the material containing the metal element described above and the conductive material containing nitrogen are combined. Alternatively, a laminated structure may be employed in which the material containing the metal element described above, the conductive material containing oxygen, and the conductive material containing nitrogen are combined.

Note that in the case where an oxide is used for a channel formation region of a transistor, a stacked-layer structure in which the above-described material containing the metal element and a conductive material containing oxygen are combined is used for a conductor functioning as a gate electrode. is preferred. In this case, a conductive material containing oxygen is preferably provided on the channel formation region side. By providing the conductive material containing oxygen on the channel formation region side, oxygen released from the conductive material is easily supplied to the channel formation region.

In particular, a conductive material containing oxygen and a metal element contained in a metal oxide in which a channel is formed is preferably used as a conductor functioning as a gate electrode. Alternatively, a conductive material containing the metal element and nitrogen described above may be used. For example, a conductive material containing nitrogen such as titanium nitride or tantalum nitride may be used. Further, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, and silicon were added. Indium tin oxide may also be used. Alternatively, indium gallium zinc oxide containing nitrogen may be used. By using such a material, hydrogen contained in the metal oxide in which the channel is formed can be captured in some cases. Alternatively, it may be possible to capture hydrogen mixed from an outer insulator or the like.

<<metal oxide>>
A metal oxide (oxide semiconductor) that functions as a semiconductor is preferably used as the oxide 230 . Metal oxides applicable to the oxide 230 according to the present invention are described below.

The metal oxide preferably contains at least indium or zinc. In particular, it preferably contains indium and zinc. In addition to these, it is preferable that aluminum, gallium, yttrium, tin, and the like are contained. Further, one or more selected from boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, cobalt, etc. may be contained.

Consider here the case where the metal oxide is an In-M-Zn oxide with indium, the element M and zinc. Note that the element M is aluminum, gallium, yttrium, or tin. Other elements applicable to element M include boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and cobalt. However, as the element M, there are cases where a plurality of the above elements may be combined. In particular, the element M is preferably one or more selected from gallium, aluminum, yttrium, and tin.

In particular, an oxide containing indium (In), gallium (Ga), and zinc (Zn) (also referred to as IGZO) is preferably used for a semiconductor layer of a transistor. Alternatively, an oxide containing indium (In), aluminum (Al), and zinc (Zn) (also referred to as IAZO) may be used for the semiconductor layer of the transistor. Alternatively, an oxide (IAGZO or IGAZO) containing indium (In), aluminum (Al), gallium (Ga), and zinc (Zn) may be used as the semiconductor layer.

In this specification and the like, metal oxides containing nitrogen may also be collectively referred to as metal oxides. A metal oxide containing nitrogen may also be referred to as a metal oxynitride.

Hereinafter, an oxide containing indium (In), gallium (Ga), and zinc (Zn) will be described as an example of a metal oxide. Note that an oxide containing indium (In), gallium (Ga), and zinc (Zn) is sometimes called an In--Ga--Zn oxide.

<Classification of crystal structure>
Crystal structures of oxide semiconductors include amorphous (including completely amorphous), CAAC (c-axis-aligned crystalline), nc (nanocrystalline), CAC (cloud-aligned composite), single crystal, and polycrystal. (poly crystal) and the like.

Note that the crystal structure of the film or substrate can be evaluated using an X-ray diffraction (XRD) spectrum. For example, it can be evaluated using an XRD spectrum obtained by GIXD (Grazing-Incidence XRD) measurement. The GIXD method is also called a thin film method or a Seemann-Bohlin method. Moreover, hereinafter, the XRD spectrum obtained by the GIXD measurement may be simply referred to as the XRD spectrum.

For example, in a quartz glass substrate, the peak shape of the XRD spectrum is almost symmetrical. On the other hand, in the In--Ga--Zn oxide film having a crystal structure, the shape of the peak of the XRD spectrum is left-right asymmetric. The asymmetric shape of the peaks in the XRD spectra demonstrates the presence of crystals in the film or substrate. In other words, the film or substrate cannot be said to be in an amorphous state unless the shape of the peaks in the XRD spectrum is symmetrical.

In addition, the crystal structure of the film or substrate can be evaluated by a diffraction pattern (also referred to as a nanobeam electron diffraction pattern) observed by nano beam electron diffraction (NBED). For example, a halo is observed in the diffraction pattern of a quartz glass substrate, and it can be confirmed that the quartz glass is in an amorphous state. Moreover, in the diffraction pattern of the In--Ga--Zn oxide film formed at room temperature, a spot-like pattern is observed instead of a halo. For this reason, it is presumed that it cannot be concluded that the In-Ga-Zn oxide deposited at room temperature is in an intermediate state, neither single crystal nor polycrystal, nor amorphous state, and is in an amorphous state. be done.

<<Structure of Oxide Semiconductor>>
Note that oxide semiconductors may be classified differently from the above when their structures are focused. For example, oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors. Non-single-crystal oxide semiconductors include, for example, the above CAAC-OS and nc-OS. Non-single-crystal oxide semiconductors include polycrystalline oxide semiconductors, amorphous-like oxide semiconductors (a-like OS), amorphous oxide semiconductors, and the like.

Details of the CAAC-OS, nc-OS, and a-like OS described above will now be described.

[CAAC-OS]
A CAAC-OS is an oxide semiconductor that includes a plurality of crystal regions, and the c-axes of the plurality of crystal regions are oriented in a specific direction. Note that the specific direction is the thickness direction of the CAAC-OS film, the normal direction to the formation surface of the CAAC-OS film, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region having periodicity in atomic arrangement. If the atomic arrangement is regarded as a lattice arrangement, the crystalline region is also a region with a uniform lattice arrangement. Furthermore, CAAC-OS has a region where a plurality of crystal regions are connected in the a-b plane direction, and the region may have strain. The strain refers to a portion where the orientation of the lattice arrangement changes between a region with a uniform lattice arrangement and another region with a uniform lattice arrangement in a region where a plurality of crystal regions are connected. That is, CAAC-OS is an oxide semiconductor that is c-axis oriented and has no obvious orientation in the ab plane direction.

Note that each of the plurality of crystal regions is composed of one or a plurality of minute crystals (crystals having a maximum diameter of less than 10 nm). When the crystalline region is composed of one minute crystal, the maximum diameter of the crystalline region is less than 10 nm. Further, when the crystal region is composed of a large number of minute crystals, the maximum diameter of the crystal region may be about several tens of nanometers.

In the In—Ga—Zn oxide, the CAAC-OS includes a layer containing indium (In) and oxygen (hereinafter referred to as an In layer) and a layer containing gallium (Ga), zinc (Zn) and oxygen ( Hereinafter, it tends to have a layered crystal structure (also referred to as a layered structure) in which (Ga, Zn) layers are laminated. Note that indium and gallium can be substituted for each other. Therefore, the (Ga, Zn) layer may contain indium. Also, the In layer may contain gallium. Note that the In layer may contain zinc. The layered structure is observed as a lattice image in, for example, a high-resolution TEM (Transmission Electron Microscope) image.

When structural analysis is performed on the CAAC-OS film using, for example, an XRD device, the out-of-plane XRD measurement using a θ/2θ scan shows that the peak indicating the c-axis orientation is at or near 2θ=31°. detected at Note that the position of the peak indicating the c-axis orientation (value of 2θ) may vary depending on the type and composition of the metal elements forming the CAAC-OS.

Further, for example, a plurality of bright points (spots) are observed in the electron beam diffraction pattern of the CAAC-OS film. A certain spot and another spot are observed at point-symmetrical positions with respect to the spot of the incident electron beam that has passed through the sample (also referred to as a direct spot) as the center of symmetry.

When the crystal region is observed from the above specific direction, the lattice arrangement in the crystal region is basically a hexagonal lattice, but the unit lattice is not always regular hexagon and may be non-regular hexagon. Moreover, the distortion may have a lattice arrangement such as a pentagon or a heptagon. Note that in CAAC-OS, no clear crystal grain boundary can be observed even near the strain. That is, it can be seen that the distortion of the lattice arrangement suppresses the formation of grain boundaries. This is because the CAAC-OS can tolerate strain due to the fact that the arrangement of oxygen atoms is not dense in the ab plane direction and the bond distance between atoms changes due to the substitution of metal atoms. it is conceivable that.

A crystal structure in which clear grain boundaries are confirmed is called a so-called polycrystal. A grain boundary becomes a recombination center, traps carriers, and is highly likely to cause a decrease in on-current of a transistor, a decrease in field-effect mobility, and the like. Therefore, a CAAC-OS in which no clear grain boundaries are observed is one of crystalline oxides having a crystal structure suitable for a semiconductor layer of a transistor. Note that a structure containing Zn is preferable for forming a CAAC-OS. For example, In--Zn oxide and In--Ga--Zn oxide are preferable because they can suppress the generation of grain boundaries more than In oxide.

A CAAC-OS is an oxide semiconductor with high crystallinity and no clear grain boundaries. Therefore, it can be said that the decrease in electron mobility due to grain boundaries is less likely to occur in CAAC-OS. In addition, since the crystallinity of an oxide semiconductor may be deteriorated due to contamination of impurities, generation of defects, or the like, CAAC-OS can be said to be an oxide semiconductor with few impurities and defects (such as oxygen vacancies). Therefore, an oxide semiconductor including CAAC-OS has stable physical properties. Therefore, an oxide semiconductor including CAAC-OS is resistant to heat and has high reliability. CAAC-OS is also stable against high temperatures (so-called thermal budget) in the manufacturing process. Therefore, when a CAAC-OS is used for a transistor including a metal oxide in a channel formation region (sometimes referred to as an OS transistor), the degree of freedom in the manufacturing process can be increased.

[nc-OS]
The nc-OS has periodic atomic arrangement in a minute region (eg, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In other words, the nc-OS has minute crystals. In addition, since the size of the minute crystal is, for example, 1 nm or more and 10 nm or less, particularly 1 nm or more and 3 nm or less, the minute crystal is also called a nanocrystal. In addition, nc-OS does not show regularity in crystal orientation between different nanocrystals. Therefore, no orientation is observed in the entire film. Therefore, an nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor depending on the analysis method. For example, when an nc-OS film is subjected to structural analysis using an XRD apparatus, out-of-plane XRD measurement using θ/2θ scanning does not detect a peak indicating crystallinity. Further, when an nc-OS film is subjected to electron beam diffraction (also referred to as selected area electron beam diffraction) using an electron beam with a probe diameter larger than that of nanocrystals (for example, 50 nm or more), a diffraction pattern like a halo pattern is obtained. Observed. On the other hand, when an nc-OS film is subjected to electron diffraction (also referred to as nanobeam electron diffraction) using an electron beam with a probe diameter close to or smaller than the nanocrystal size (for example, 1 nm or more and 30 nm or less), direct In some cases, an electron beam diffraction pattern is obtained in which a plurality of spots are observed within a ring-shaped area centered on the spot.

[a-like OS]
An a-like OS is an oxide semiconductor having a structure between an nc-OS and an amorphous oxide semiconductor. An a-like OS has void or low density regions. That is, a-like OS has lower crystallinity than nc-OS and CAAC-OS. In addition, the a-like OS has a higher hydrogen concentration in the film than the nc-OS and the CAAC-OS.

<<Structure of Oxide Semiconductor>>
Next, the details of the above CAC-OS will be described. Note that CAC-OS relates to material composition.

[CAC-OS]
A CAC-OS is, for example, one structure of a material in which elements constituting a metal oxide are unevenly distributed with a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or less, or in the vicinity thereof. In the following, in the metal oxide, one or more metal elements are unevenly distributed, and the region having the metal element has a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or less, or a size in the vicinity thereof. The mixed state is also called mosaic or patch.

Furthermore, the CAC-OS is a structure in which the material is separated into a first region and a second region to form a mosaic shape, and the first region is distributed in the film (hereinafter, also referred to as a cloud shape). is called). That is, CAC-OS is a composite metal oxide in which the first region and the second region are mixed.

Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In—Ga—Zn oxide are represented by [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in In—Ga—Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is greater than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region in which [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region in which [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

Specifically, the first region is a region containing indium oxide, indium zinc oxide, or the like as a main component. The second region is a region containing gallium oxide, gallium zinc oxide, or the like as a main component. That is, the first region can be rephrased as a region containing In as a main component. Also, the second region can be rephrased as a region containing Ga as a main component.

In some cases, a clear boundary cannot be observed between the first region and the second region.

In addition, the CAC-OS in the In—Ga—Zn oxide means a region containing Ga as a main component and a region containing In as a main component in a material structure containing In, Ga, Zn, and O. Each region is a mosaic, and refers to a configuration in which these regions exist randomly. Therefore, CAC-OS is presumed to have a structure in which metal elements are unevenly distributed.

A CAC-OS can be formed, for example, by a sputtering method under conditions in which the substrate is not heated. When the CAC-OS is formed by a sputtering method, one or more selected from an inert gas (typically argon), oxygen gas, and nitrogen gas may be used as the film formation gas. good. Further, the flow rate ratio of the oxygen gas to the total flow rate of the film forming gas during film formation is preferably as low as possible. For example, the flow ratio of the oxygen gas to the total flow rate of the film forming gas during film formation is 0% or more and less than 30%, preferably 0% or more and 10% or less.

Further, for example, in the CAC-OS in In-Ga-Zn oxide, an EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) shows that a region containing In as a main component It can be confirmed that the (first region) and the region (second region) containing Ga as the main component are unevenly distributed and have a mixed structure.

Here, the first region is a region with higher conductivity than the second region. That is, when carriers flow through the first region, conductivity as a metal oxide is developed. Therefore, by distributing the first region in the form of a cloud in the metal oxide, a high field effect mobility (μ) can be realized.

On the other hand, the second region is a region with higher insulation than the first region. In other words, the leakage current can be suppressed by distributing the second region in the metal oxide.

Therefore, when the CAC-OS is used for a transistor, the conductivity caused by the first region and the insulation caused by the second region act complementarily to provide a switching function (on/off). functions) can be given to the CAC-OS. In other words, in CAC-OS, a part of the material has a conductive function, a part of the material has an insulating function, and the whole material has a semiconductor function. By separating the conductive and insulating functions, both functions can be maximized. Therefore, by using a CAC-OS for a transistor, high on-state current (I _on ), high field-effect mobility (μ), and favorable switching operation can be achieved.

Further, a transistor using a CAC-OS has high reliability. Therefore, CAC-OS is most suitable for various semiconductor devices including display devices.

Oxide semiconductors have various structures and each has different characteristics. An oxide semiconductor of one embodiment of the present invention includes two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS. may

<Transistor including oxide semiconductor>
Next, the case where the above oxide semiconductor is used for a transistor is described.

By using the above oxide semiconductor for a transistor, a transistor with high field-effect mobility can be realized. Further, a highly reliable transistor can be realized.

An oxide semiconductor with low carrier concentration is preferably used for a transistor. For example, the carrier concentration of the oxide semiconductor is 1×10 ¹⁷ cm ⁻³ or less, preferably 1×10 ¹⁵ cm ⁻³ or less, more preferably 1×10 ¹³ cm ⁻³ or less, more preferably 1×10 ¹¹ cm −3 or less ^{. 3} or less, more preferably less than 1×10 ¹⁰ cm ⁻³ and 1×10 ⁻⁹ cm ⁻³ or more. Note that in the case of lowering the carrier concentration of the oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be lowered to lower the defect level density. In this specification and the like, a low impurity concentration and a low defect level density are referred to as high-purity intrinsic or substantially high-purity intrinsic. Note that an oxide semiconductor with a low carrier concentration is sometimes referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor.

Further, since a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low defect level density, the trap level density may also be low.

In addition, the charge trapped in the trap level of the oxide semiconductor takes a long time to disappear and may behave like a fixed charge. Therefore, a transistor whose channel formation region is formed in an oxide semiconductor with a high trap level density might have unstable electrical characteristics.

Therefore, it is effective to reduce the impurity concentration in the oxide semiconductor in order to stabilize the electrical characteristics of the transistor. In order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in adjacent films. Impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like. Note that the impurities in the oxide semiconductor refer to, for example, substances other than the main components of the oxide semiconductor. For example, an element whose concentration is less than 0.1 atomic percent can be said to be an impurity.

<Impurities>
Here, the influence of each impurity in the oxide semiconductor is described.

When an oxide semiconductor contains silicon or carbon, which is one of Group 14 elements, a defect level is formed in the oxide semiconductor. Therefore, the concentration of silicon or carbon in the oxide semiconductor (concentration obtained by secondary ion mass spectrometry (SIMS)) is 2× ¹⁰ atoms/cm ^or less, preferably 2×10 ¹⁷ atoms/cm ³ or less.

Further, when an oxide semiconductor contains an alkali metal or an alkaline earth metal, a defect level may be formed to generate carriers. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal tends to have normally-on characteristics. Therefore, the concentration of alkali metal or alkaline earth metal in the oxide semiconductor obtained by SIMS is set to 1×10 ¹⁸ atoms/cm ³ or less, preferably 2×10 ¹⁶ atoms/cm ³ or less.

In addition, when an oxide semiconductor contains nitrogen, electrons as carriers are generated, the carrier concentration increases, and the oxide semiconductor tends to be n-type. As a result, a transistor including an oxide semiconductor containing nitrogen as a semiconductor tends to have normally-on characteristics. Alternatively, when an oxide semiconductor contains nitrogen, a trap level may be formed. As a result, the electrical characteristics of the transistor may become unstable. Therefore, the nitrogen concentration in the oxide semiconductor obtained by SIMS is less than 5×10 ¹⁹ atoms/cm ³ , preferably 5×10 ¹⁸ atoms/cm ³ or less, more preferably 1×10 ¹⁸ atoms/cm ³ or less. , more preferably 5×10 ¹⁷ atoms/cm ³ or less.

Further, hydrogen contained in the oxide semiconductor reacts with oxygen that bonds to a metal atom to form water, which may cause oxygen vacancies. When hydrogen enters the oxygen vacancies, electrons, which are carriers, may be generated. In addition, part of hydrogen may bond with oxygen that bonds with a metal atom to generate an electron, which is a carrier. Therefore, a transistor including an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. Therefore, hydrogen in the oxide semiconductor is preferably reduced as much as possible. Specifically, the hydrogen concentration in the oxide semiconductor obtained by SIMS is less than 1×10 ²⁰ atoms/cm ³ , preferably less than 1×10 ¹⁹ atoms/cm ³ , more preferably 5×10 ¹⁸ atoms/cm. Less than ³ , more preferably less than 1×10 ¹⁸ atoms/cm ³ .

By using an oxide semiconductor in which impurities are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be imparted.

<<Other semiconductor materials>>
Semiconductor materials that can be used for oxide 230 are not limited to the metal oxides described above. A semiconductor material having a bandgap (a semiconductor material that is not a zero-gap semiconductor) may be used as the oxide 230 . For example, it is preferable to use a single element semiconductor such as silicon, a compound semiconductor such as gallium arsenide, a layered substance (also referred to as an atomic layer substance, a two-dimensional material, or the like) that functions as a semiconductor, or the like as the semiconductor material. In particular, it is preferable to use a layered substance that functions as a semiconductor as the semiconductor material.

Here, in this specification and the like, a layered substance is a general term for a group of materials having a layered crystal structure. A layered crystal structure is a structure in which layers formed by covalent or ionic bonds are stacked via bonds such as van der Waals forces that are weaker than covalent or ionic bonds. A layered material has high electrical conductivity within a unit layer, that is, high two-dimensional electrical conductivity. By using a material that functions as a semiconductor and has high two-dimensional electrical conductivity for the channel formation region, a transistor with high on-state current can be provided.

Layered materials include graphene, silicene, and chalcogenides. Chalcogenides are compounds that contain chalcogens. Chalcogen is a general term for elements belonging to Group 16, and includes oxygen, sulfur, selenium, tellurium, polonium, and livermorium. Chalcogenides include transition metal chalcogenides and Group 13 chalcogenides.

As the oxide 230, it is preferable to use, for example, a transition metal chalcogenide that functions as a semiconductor. Specific examples of transition metal chalcogenides applicable as the oxide 230 include molybdenum sulfide (typically MoS ₂ ), molybdenum selenide (typically MoSe ₂ ), and molybdenum tellurium (typically MoTe ₂ ). , tungsten sulfide (typically WS ₂ ), tungsten selenide (typically WSe ₂ ), tungsten tellurium (typically WTe ₂ ), hafnium sulfide (typically HfS ₂ ), hafnium selenide (typically typically HfSe ₂ ), zirconium sulfide (typically ZrS ₂ ), zirconium selenide (typically ZrSe ₂ ), and the like. By applying the transition metal chalcogenide described above to the oxide 230, a semiconductor device with a large on-current can be provided.

<Modified Example of Semiconductor Device>
An example of a semiconductor device that is one embodiment of the present invention is described below with reference to FIGS. 14A to 14D.

FIG. 14A shows a top view of a semiconductor device. FIG. 14B is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line of A1-A2 shown in FIG. 14A. Also, FIG. 14C is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A3-A4 in FIG. 14A. FIG. 14D is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A5-A6 in FIG. 14A. The top view of FIG. 14A omits some elements for clarity of illustration.

Note that in the semiconductor devices illustrated in FIGS. 14A to 14D , structures having the same functions as structures constituting the semiconductor devices illustrated in <Structure Example of Semiconductor Device> are denoted by the same reference numerals. Note that in this item as well, the materials described in detail in <Structure Example of Semiconductor Device> can be used as constituent materials of the semiconductor device.

The semiconductor device shown in FIGS. 14A to 14D is a modification of the semiconductor device shown in FIGS. 9A to 9D. The semiconductor devices shown in FIGS. 14A to 14D are different from the semiconductor devices shown in FIGS. 9A to 9D in that insulators 283 and 221 are provided.

The insulator 283 is provided between the insulator 282 and the insulator 285 . An insulator having a function of suppressing diffusion of hydrogen is preferably used as the insulator 283 . Accordingly, diffusion of hydrogen into the transistor 200 from above the insulator 283 can be suppressed. Note that an insulator that can be used for the insulator 275 described above may be used as the insulator 283 . For example, silicon nitride deposited by a sputtering method may be used as the insulator 283 . By forming the insulator 283 by a sputtering method, a silicon nitride film with high density can be formed. Alternatively, as the insulator 283, silicon nitride deposited by a PEALD method or a CVD method may be stacked over silicon nitride deposited by a sputtering method.

By providing the insulator 282 having a function of capturing impurities such as hydrogen in contact with the insulator 280 in a region sandwiched between the insulator 212 and the insulator 283, hydrogen and the like contained in the insulator 280 and the like can be removed. Impurities can be trapped and the amount of hydrogen in the region can be made constant. In particular, it is preferable to use aluminum oxide having an amorphous structure as the insulator 282 because hydrogen can be trapped or fixed more effectively in some cases. Accordingly, the transistor 200 and the semiconductor device with favorable characteristics and high reliability can be manufactured.

Although the transistor 200 illustrated in FIGS. 14A to 14D shows a structure in which the insulator 283 is provided as a single layer, the present invention is not limited to this. For example, the insulator 283 may be provided as a stacked structure of two or more layers.

For example, when the insulator 283 has a two-layer structure, a silicon nitride film is formed as a lower layer of the insulator 283 by a sputtering method, and a silicon nitride film is formed as an upper layer of the insulator 283 by an ALD method. You may The hydrogen concentration in the lower layer of the insulator 282 can be reduced by using a sputtering method that does not require the use of molecules containing hydrogen in the deposition gas. Furthermore, when a pinhole or a discontinuity is formed in a film formed by a sputtering method, a film formed by an ALD method with good coverage is used to block the overlapping portion of the pinhole or discontinuity. be able to.

Note that in the case where the insulator 283 has a two-layer structure, part of the top surface of the upper layer of the insulator 283 may be removed. Also, it may be difficult to clearly detect the boundary between the upper layer and the lower layer of the insulator 283 .

The insulator 221 is provided between the insulator 216 and the conductor 205 and the insulator 222 . The insulator 221 preferably has a function of suppressing diffusion of hydrogen. Accordingly, diffusion of hydrogen into the transistor 200 from below the insulator 221 can be suppressed. Note that the insulator 221 can also function as the insulator 212 . In such a case, the structure without the insulator 212 can simplify the manufacturing process of the semiconductor device and improve productivity.

Note that an insulator that can be used for the above insulator 275 may be used as the insulator 221 . For example, it is preferable to use silicon nitride deposited by an ALD method (especially a PEALD method) as the insulator 221 . By using the ALD method for depositing the insulator 221, the insulator 221 can be deposited with good coverage even when unevenness is formed between the insulator 216 and the conductor 205. FIG. Therefore, formation of a pinhole, a disconnection, or the like in the insulator 222 formed over the insulator 221 can be suppressed.

Further, an insulator having a function of suppressing diffusion of hydrogen may be provided between the insulator 222 and the insulator 224 . Accordingly, diffusion of hydrogen into the transistor 200 from below the insulator can be suppressed.

Alternatively, as shown in FIGS. 14B and 14C, the conductor 205 may have a three-layer laminated structure of a conductor 205a, a conductor 205b, and a conductor 205c. The conductor 205c is provided in contact with the upper surface of the conductor 205b. A structure in which the side surface of the conductor 205c is in contact with the conductor 205a may be employed. Alternatively, the upper surface of the conductor 205c and the uppermost portion of the conductor 205a may be substantially aligned.

As with the conductor 205a, the conductor 205c is preferably made of a conductive material that has a function of reducing diffusion of hydrogen. Thus, the conductor 205b can be wrapped with the conductor 205a and the conductor 205c, so that impurities such as hydrogen contained in the conductor 205b diffuse into the oxide 230 through the insulators 216, 224, and the like. can prevent you from doing it. In addition, by using a conductive material having a function of suppressing diffusion of oxygen for the conductors 205a and 205c, it is possible to suppress oxidation of the conductor 205b and a decrease in conductivity.

An OS transistor such as the transistor 200 has little change in electrical characteristics due to irradiation with radiation, that is, has high resistance to radiation; For example, OS transistors can be suitably used when used in outer space. Specifically, the OS transistor can be used as a transistor included in a semiconductor device provided in a space shuttle, an artificial satellite, a space probe, or the like. Radiation includes, for example, X-rays, neutron beams, and the like. In addition, outer space refers to, for example, an altitude of 100 km or more, but the outer space described in this specification may include the thermosphere, the mesosphere, and the stratosphere.

Alternatively, for example, the OS transistor can be used as a transistor that constitutes a semiconductor device provided in a nuclear power plant, a radioactive waste disposal site, or a working robot in a disposal site. In particular, it can be suitably used for a transistor that constitutes a semiconductor device provided in a remote-controlled robot that is remotely controlled for dismantling nuclear reactor facilities, retrieving nuclear fuel or fuel debris, and conducting field surveys in spaces with a large amount of radioactive materials.

One embodiment of the present invention can provide a novel transistor. Alternatively, a semiconductor device that can be miniaturized or highly integrated can be provided. Alternatively, a semiconductor device with favorable frequency characteristics can be provided. Alternatively, a semiconductor device with high operating speed can be provided. Alternatively, a semiconductor device with little variation in transistor characteristics can be provided. Alternatively, a semiconductor device with favorable electrical characteristics can be provided. Alternatively, a highly reliable semiconductor device can be provided. Alternatively, a semiconductor device with large on-current can be provided. Alternatively, a semiconductor device with high field effect mobility can be provided. Alternatively, a semiconductor device with low power consumption can be provided.

The structure described in this embodiment can be combined as appropriate with any of the structures described in other embodiments.

(Embodiment 3)
FIG. 15 illustrates a cross-sectional structure example of the storage device 100 according to one embodiment of the present invention. The memory device 100 shown in FIG. 15 has multiple layers of memory layers 60 above the drive circuit layer 50 . In order to reduce the repetition of the description, the description of the memory layer 60 in this embodiment is omitted.

In addition, FIG. 15 illustrates the transistor 400 included in the driver circuit layer 50 . Transistor 400 is provided on substrate 311 and includes a conductor 316 functioning as a gate, an insulator 315 functioning as a gate insulator, a semiconductor region 313 comprising part of substrate 311, and a lower region functioning as a source or drain region. It has a resistance region 314a and a low resistance region 314b. Transistor 400 can be either a p-channel transistor or an n-channel transistor. As the substrate 311, for example, a single crystal silicon substrate can be used.

Here, in the transistor 400 shown in FIG. 15, the semiconductor region 313 (part of the substrate 311) in which the channel is formed has a convex shape. A conductor 316 is provided to cover the side and top surfaces of the semiconductor region 313 with an insulator 315 interposed therebetween. Note that the conductor 316 may be made of a material that adjusts the work function. Such a transistor 400 is also called a FIN transistor because it utilizes the projections of the semiconductor substrate. Note that an insulator that functions as a mask for forming the protrusion may be provided in contact with the upper portion of the protrusion. Further, here, the case where a part of the semiconductor substrate is processed to form a convex portion is shown, but a SOI (Silicon Insulator) substrate may be processed to form a semiconductor film having a convex shape.

Note that the transistor 400 illustrated in FIG. 15 is an example, and the structure thereof is not limited, and an appropriate transistor may be used depending on the circuit configuration or driving method.

A wiring layer provided with an interlayer film, a wiring, a plug, and the like may be provided between the structures. Also, the wiring layer can be provided in a plurality of layers depending on the design. Further, in this specification and the like, the wiring and the plug electrically connected to the wiring may be integrated. That is, there are cases where a part of the conductor functions as a wiring and a part of the conductor functions as a plug.

For example, an insulator 320 , an insulator 322 , an insulator 324 , and an insulator 326 are stacked in this order over the transistor 400 as interlayer films. A conductor 328 or the like is embedded in the insulator 320 and the insulator 322 . A conductor 330 or the like is embedded in the insulators 324 and 326 . Note that the conductor 328 and the conductor 330 function as contact plugs or wirings.

In addition, the insulator functioning as an interlayer film may function as a planarization film covering the uneven shape thereunder. For example, the top surface of the insulator 322 may be planarized by planarization treatment using a chemical mechanical polishing (CMP) method or the like in order to improve planarity.

A wiring layer may be provided over the insulator 326 and the conductor 330 . For example, in FIG. 15, an insulator 350 , an insulator 357 , an insulator 352 , and an insulator 354 are stacked in this order over the insulator 326 and the conductor 330 . A conductor 356 is formed over the insulators 350 , 357 , and 352 . Conductors 356 function as contact plugs or traces.

An insulator 354 is provided over the insulator 352 and the conductor 356 . A conductor 358 is embedded in the insulator 354 . Conductors 358 function as contact plugs or traces. For example, the wiring SL and the transistor 400 are electrically connected through the conductors 358, 356, 330, and the like.

This embodiment can be appropriately combined with other embodiments and the like described in this specification.

(Embodiment 4)
In this embodiment mode, an example of an electronic component in which the storage device or the like described in the above embodiment mode is incorporated will be described.

<Electronic parts>
FIG. 16A shows a perspective view of electronic component 700 and a substrate (mounting substrate 704) on which electronic component 700 is mounted. An electronic component 700 illustrated in FIG. 16A includes a memory device 100, which is a type of semiconductor device according to one embodiment of the present invention, in a mold 711. The memory device 100 is a type of semiconductor device according to one embodiment of the present invention. FIG. 16A omits part of the description to show the inside of electronic component 700 . Electronic component 700 has lands 712 outside mold 711 . Land 712 is electrically connected to electrode pad 713 , and electrode pad 713 is electrically connected to storage device 100 via wire 714 . The electronic component 700 is mounted on a printed circuit board 702, for example. A mounting board 704 is completed by combining a plurality of such electronic components and electrically connecting them on the printed board 702 .

As shown in the above embodiment, the memory device 100 has the drive circuit layer 50, the memory layer 60, and the memory array 15. FIG.

FIG. 16B shows a perspective view of electronic component 730 . Electronic component 730 is an example of SiP (System in package) or MCM (Multi Chip Module). An electronic component 730 has an interposer 731 provided on a package substrate 732 (printed circuit board), and a semiconductor device 735 and a plurality of storage devices 100 provided on the interposer 731 .

Electronic component 730 shows an example in which storage device 100 is used as a high bandwidth memory (HBM). For the semiconductor device 735, an integrated circuit (semiconductor device) such as a CPU, GPU, or FPGA can be used.

A ceramic substrate, a plastic substrate, a glass epoxy substrate, or the like can be used for the package substrate 732 . A silicon interposer, a resin interposer, or the like can be used as the interposer 731 .

The interposer 731 has a plurality of wirings and has a function of electrically connecting a plurality of integrated circuits with different terminal pitches. A plurality of wirings are provided in a single layer or multiple layers. The interposer 731 also has a function of electrically connecting the integrated circuit provided over the interposer 731 to electrodes provided over the package substrate 732 . For these reasons, the interposer is sometimes called a "rewiring board" or an "intermediate board". In some cases, through electrodes are provided in the interposer 731 and the integrated circuit and the package substrate 732 are electrically connected using the through electrodes. Also, in a silicon interposer, a TSV (Through Silicon Via) can be used as a through electrode.

A silicon interposer is preferably used as the interposer 731 . Since silicon interposers do not require active elements, they can be manufactured at a lower cost than integrated circuits. On the other hand, since the wiring of the silicon interposer can be formed by a semiconductor process, it is easy to form fine wiring, which is difficult with the resin interposer.

HBM requires many interconnects to achieve a wide memory bandwidth. Therefore, an interposer for mounting an HBM is required to form fine and high-density wiring. Therefore, it is preferable to use a silicon interposer for the interposer that mounts the HBM.

In addition, in SiP, MCM, etc. using a silicon interposer, deterioration of reliability due to a difference in coefficient of expansion between the integrated circuit and the interposer is unlikely to occur. In addition, since the silicon interposer has a highly flat surface, poor connection between the integrated circuit provided on the silicon interposer and the silicon interposer is less likely to occur. In particular, in a 2.5D package (2.5-dimensional packaging) in which a plurality of integrated circuits are arranged side by side on an interposer, it is preferable to use a silicon interposer.

Also, a heat sink (radiating plate) may be provided overlapping with the electronic component 730 . When a heat sink is provided, it is preferable that the heights of the integrated circuits provided over the interposer 731 be uniform. For example, in the electronic component 730 described in this embodiment, it is preferable that the memory device 100 and the semiconductor device 735 have the same height.

Electrodes 733 may be provided on the bottom of the package substrate 732 in order to mount the electronic component 730 on another substrate. FIG. 16B shows an example in which the electrodes 733 are formed from solder balls. BGA (Ball Grid Array) mounting can be achieved by providing solder balls in a matrix on the bottom of the package substrate 732 . Alternatively, the electrodes 733 may be formed of conductive pins. PGA (Pin Grid Array) mounting can be achieved by providing conductive pins in a matrix on the bottom of the package substrate 732 .

The electronic component 730 can be mounted on other boards using various mounting methods, not limited to BGA and PGA. For example, SPGA (Staggered Pin Grid Array), LGA (Land Grid Array), QFP (Quad Flat Package), QFJ (Quad Flat J-leaded package), or QFN (Quad Flat Non-leaded package) Use an implementation method such as be able to.

This embodiment can be appropriately combined with other embodiments and the like described in this specification.

(Embodiment 5)
In this embodiment, application examples of the memory device according to one embodiment of the present invention will be described.

The storage device according to one aspect of the present invention is, for example, storage of various electronic devices (for example, information terminals, computers, smartphones, electronic book terminals, digital still cameras, video cameras, recording/playback devices, navigation systems, game machines, etc.) applicable to equipment. It can also be used for image sensors, IoT (Internet of Things), healthcare-related equipment, and the like. Here, the computer includes a tablet computer, a notebook computer, a desktop computer, and a large computer such as a server system.

An example of an electronic device including a memory device according to one embodiment of the present invention will be described. 17A to 17J and FIGS. 18A to 18E illustrate how the electronic component 700 or the electronic component 730 having the storage device is included in each electronic device.

[mobile phone]
An information terminal 5500 shown in FIG. 17A is a mobile phone (smartphone), which is a type of information terminal. The information terminal 5500 includes a housing 5510 and a display portion 5511. As an input interface, the display portion 5511 is provided with a touch panel, and the housing 5510 is provided with buttons.

By applying the storage device according to one embodiment of the present invention, the information terminal 5500 can hold temporary files generated when an application is executed (for example, a cache when using a web browser).

[Wearable terminal]
Also, FIG. 17B illustrates an information terminal 5900 that is an example of a wearable terminal. An information terminal 5900 includes a housing 5901, a display portion 5902, operation switches 5903 and 5904, a band 5905, and the like.

By using the storage device according to one embodiment of the present invention, the wearable terminal can hold temporary files generated when an application is executed, like the information terminal 5500 described above.

[Information terminal]
A desktop information terminal 5300 is also illustrated in FIG. 17C. A desktop information terminal 5300 includes an information terminal main body 5301 , a display section 5302 , and a keyboard 5303 .

Similar to the information terminal 5500 described above, the desktop information terminal 5300 can hold temporary files generated when an application is executed by applying the storage device according to one embodiment of the present invention.

In the above description, smartphones, wearable terminals, and desktop information terminals are illustrated as examples of electronic devices in FIGS. 17A to 17C. can. Examples of information terminals other than smart phones, wearable terminals, and desktop information terminals include PDAs (Personal Digital Assistants), laptop information terminals, and workstations.

[electric appliances]
FIG. 17D also shows an electric refrigerator-freezer 5800 as an example of an electrical appliance. The electric freezer-refrigerator 5800 has a housing 5801, a refrigerator compartment door 5802, a freezer compartment door 5803, and the like. For example, the electric freezer-refrigerator 5800 is an electric freezer-refrigerator compatible with IoT (Internet of Things).

The storage device according to one embodiment of the present invention can be applied to the electric refrigerator-freezer 5800 . The electric freezer-refrigerator 5800 can transmit and receive information such as foodstuffs stored in the electric freezer-refrigerator 5800 and expiration dates of the foodstuffs to and from an information terminal or the like via the Internet or the like. The electric refrigerator-freezer 5800 can hold a temporary file generated when transmitting the information in the semiconductor device.

In this example, an electric refrigerator/freezer was explained as an electric appliance, but other electric appliances include, for example, a vacuum cleaner, a microwave oven, an electric oven, a rice cooker, a water heater, an IH cooker, a water server, and an air conditioner. Appliances, washing machines, dryers, audiovisual equipment, etc.

[game machine]
FIG. 17E also illustrates a portable game machine 5200, which is an example of a game machine. A portable game machine 5200 includes a housing 5201, a display portion 5202, buttons 5203, and the like.

Furthermore, FIG. 17F illustrates a stationary game machine 7500, which is an example of a game machine. A stationary game machine 7500 has a main body 7520 and a controller 7522 . Note that a controller 7522 can be connected to the main body 7520 wirelessly or by wire. In addition, although not shown in FIG. 17F, the controller 7522 can include a display unit that displays game images, a touch panel, a stick, a rotary knob, or a slide knob that serves as an input interface other than buttons. . Also, the shape of the controller 7522 is not limited to that shown in FIG. 17F, and the shape of the controller 7522 may be changed variously according to the genre of the game. For example, in shooting games such as FPS (First Person Shooter), a button can be used as a trigger and a controller shaped like a gun can be used. Further, for example, in a music game or the like, a controller shaped like a musical instrument, music equipment, or the like can be used. Furthermore, the stationary game machine may have a camera, depth sensor, microphone, etc., instead of using a controller, and may be operated by the game player's gestures or voice.

Also, the video of the game machine described above can be output by a display device such as a television device, a personal computer display, a game display, or a head-mounted display.

By applying the storage device described in the above embodiment to the portable game machine 5200 or the stationary game machine 7500, the portable game machine 5200 with low power consumption or the stationary game machine 7500 with low power consumption can be realized. . In addition, the low power consumption can reduce heat generation from the circuit, so that the influence of the heat generation on the circuit itself, the peripheral circuits, and the module can be reduced.

Furthermore, by applying the storage device described in the above embodiment to the portable game machine 5200 or the stationary game machine 7500, it is possible to hold temporary files required for calculations occurring during game execution.

A portable game machine is shown in FIG. 17E as an example of the game machine. Also, FIG. 17F shows a home-use stationary game machine. Note that the electronic device of one embodiment of the present invention is not limited to this. Examples of electronic devices of one embodiment of the present invention include arcade game machines installed in entertainment facilities (game centers, amusement parks, etc.) and pitching machines for batting practice installed in sports facilities.

[Moving body]
The storage devices described in the above embodiments can be applied to automobiles, which are mobile objects, and to the vicinity of the driver's seat of automobiles.

FIG. 17G shows an automobile 5700, which is an example of a mobile object.

Around the driver's seat of the automobile 5700 is an instrument panel that provides various information by displaying a speedometer, tachometer, mileage, fuel gauge, gear status, air conditioner settings, and the like. Further, a storage device showing such information may be provided around the driver's seat.

In particular, by displaying an image from an imaging device (not shown) provided in the automobile 5700 on the display device, it is possible to compensate for the blind spot in the driver's seat and the view obstructed by the pillars, etc., and improve safety. can be enhanced. That is, by displaying an image from an imaging device provided outside the automobile 5700, blind spots can be compensated for and safety can be enhanced.

Since the semiconductor device described in the above embodiment can temporarily hold information, for example, the storage device can be used as necessary in a system that performs automatic driving of the automobile 5700, road guidance, danger prediction, and the like. It can be used to hold temporary information. The display device may be configured to display temporary information such as road guidance and danger prediction. Also, a configuration may be adopted in which the image of the driving recorder installed in the automobile 5700 is held.

In addition, in the above description, an automobile is described as an example of a mobile object, but the mobile object is not limited to an automobile. Examples of mobile objects include trains, monorails, ships, flying objects (helicopters, unmanned aerial vehicles (drone), airplanes, rockets), and the like.

[camera]
The storage devices described in the above embodiments can be applied to cameras.

FIG. 17H illustrates a digital camera 6240 as an example of an imaging device. The digital camera 6240 has a housing 6241, a display portion 6242, an operation switch 6243, a shutter button 6244, and the like, and a detachable lens 6246 is attached to the digital camera 6240. Note that although the digital camera 6240 has a configuration in which the lens 6246 can be removed from the housing 6241 and replaced, the lens 6246 and the housing 6241 may be integrated. Further, the digital camera 6240 may have a configuration in which a strobe device, a viewfinder, and the like can be attached separately.

By applying the storage device described in the above embodiment to the digital camera 6240, the digital camera 6240 with low power consumption can be realized. In addition, the low power consumption can reduce the heat generated from the circuit, thereby reducing the influence of the heat on the circuit itself, the peripheral circuits, and the module.

[Video camera]
The storage devices described in the above embodiments can be applied to video cameras.

FIG. 17I shows a video camera 6300 as an example of an imaging device. A video camera 6300 includes a first housing 6301, a second housing 6302, a display portion 6303, operation switches 6304, a lens 6305, a connection portion 6306, and the like. The operation switch 6304 and the lens 6305 are provided on the first housing 6301 and the display section 6303 is provided on the second housing 6302 . The first housing 6301 and the second housing 6302 are connected by a connecting portion 6306, and the angle between the first housing 6301 and the second housing 6302 can be changed by the connecting portion 6306. be. The image on the display unit 6303 may be switched according to the angle between the first housing 6301 and the second housing 6302 on the connection unit 6306 .

When recording video captured by the video camera 6300, it is necessary to perform encoding according to the data recording format. By using the semiconductor device described above, the video camera 6300 can temporarily hold files generated during encoding.

[ICD]
The storage device described in the above embodiments can be applied to an implantable cardioverter defibrillator (ICD).

FIG. 17J is a schematic cross-sectional view showing an example of an ICD. The ICD body 5400 has at least a battery 5401, an electronic component 700, a regulator, a control circuit, an antenna 5404, a wire 5402 to the right atrium, and a wire 5403 to the right ventricle.

The ICD body 5400 is surgically placed in the body, and two wires are passed through the subclavian vein 5405 and the superior vena cava 5406 of the human body with one wire tip placed in the right ventricle and the other wire tip placed in the right atrium. be done.

The ICD main body 5400 has a function as a pacemaker, and paces the heart when the heart rate deviates from the prescribed range. In addition, if pacing does not improve the heart rate (fast ventricular tachycardia, ventricular fibrillation, etc.), treatment with electric shocks is performed.

The ICD body 5400 must constantly monitor heart rate in order to properly pace and deliver shocks. Therefore, the ICD main body 5400 has a sensor for detecting heart rate. In addition, the ICD main body 5400 can store the heart rate data obtained by the sensor or the like, the number of pacing treatments, the time, and the like in the electronic component 700 .

Also, power can be received by the antenna 5404 and the power is charged in the battery 5401 . In addition, the ICD main body 5400 has a plurality of batteries, so that safety can be enhanced. Specifically, even if some of the batteries in the ICD main body 5400 become unusable, the rest of the batteries can still function, so the ICD also functions as an auxiliary power source.

In addition to the antenna 5404 capable of receiving electric power, an antenna capable of transmitting physiological signals may be provided. A system may be configured to monitor various cardiac activity.

[Extension device for PC]
The semiconductor devices described in the above embodiments can be applied to computers such as PCs (Personal Computers) and expansion devices for information terminals.

FIG. 18A shows an expansion device 6100 externally attached to a PC, mounted with a portable chip capable of storing information, as an example of the expansion device. The expansion device 6100 can store information by the chip, for example, by connecting to a PC via a USB (Universal Serial Bus) or the like. Although FIG. 18A illustrates the expansion device 6100 in a portable form, the expansion device according to one aspect of the present invention is not limited to this. It may also be an expansion device in a larger form.

Expansion device 6100 has housing 6101 , cap 6102 , USB connector 6103 and substrate 6104 . A substrate 6104 is housed in a housing 6101 . The substrate 6104 is provided with a circuit for driving the semiconductor device or the like described in the above embodiment mode. For example, substrate 6104 has electronic component 700 and controller chip 6106 mounted thereon. A USB connector 6103 functions as an interface for connecting with an external device.

[SD card]
The storage devices described in the above embodiments can be applied to SD cards that can be attached to electronic devices such as information terminals and digital cameras.

FIG. 18B is a schematic diagram of the appearance of the SD card, and FIG. 18C is a schematic diagram of the internal structure of the SD card. SD card 5110 has housing 5111 , connector 5112 and substrate 5113 . A connector 5112 functions as an interface for connecting with an external device. A substrate 5113 is housed in a housing 5111 . A substrate 5113 is provided with a memory device and a circuit for driving the memory device. For example, the electronic component 700 and the controller chip 5115 are attached to the substrate 5113 . Note that the circuit configurations of the electronic component 700 and the controller chip 5115 are not limited to those described above, and the circuit configurations may be changed as appropriate according to circumstances. For example, a write circuit, a row driver, a read circuit, and the like included in the electronic component may be incorporated in the controller chip 5115 instead of the electronic component 700 .

By providing the electronic component 700 also on the back side of the substrate 5113, the capacity of the SD card 5110 can be increased. Alternatively, a wireless chip having a wireless communication function may be provided over the substrate 5113 . As a result, wireless communication can be performed between the external device and the SD card 5110, and data can be read from and written to the electronic component 700. FIG.

[SSD]
The storage devices described in the above embodiments can be applied to SSDs (Solid State Drives) that can be attached to electronic devices such as information terminals.

FIG. 18D is a schematic diagram of the appearance of the SSD, and FIG. 18E is a schematic diagram of the internal structure of the SSD. SSD 5150 has housing 5151 , connector 5152 and substrate 5153 . A connector 5152 functions as an interface for connecting with an external device. A substrate 5153 is housed in a housing 5151 . A substrate 5153 is provided with a memory device and a circuit for driving the memory device. For example, substrate 5153 has electronic component 700 , memory chip 5155 and controller chip 5156 mounted thereon. By providing the electronic component 700 also on the back side of the substrate 5153, the capacity of the SSD 5150 can be increased. The memory chip 5155 incorporates a work memory. For example, the memory chip 5155 may be a DRAM chip. The controller chip 5156 incorporates a processor, an ECC circuit, and the like. Note that the circuit configurations of the electronic component 700, the memory chip 5155, and the controller chip 5115 are not limited to those described above, and the circuit configurations may be changed as appropriate according to circumstances. For example, the controller chip 5156 may also be provided with a memory functioning as a work memory.

[calculator]
A computer 5600 shown in FIG. 19A is an example of a large computer. In the computer 5600 , a rack 5610 stores a plurality of rack-mounted computers 5620 .

Calculator 5620 may, for example, have the configuration of the perspective view shown in FIG. 19B. In FIG. 19B, a computer 5620 has a motherboard 5630, and the motherboard 5630 has a plurality of slots 5631 and a plurality of connection terminals. A PC card 5621 is inserted into the slot 5631 . In addition, the PC card 5621 has a connection terminal 5623, a connection terminal 5624, and a connection terminal 5625, which are connected to the mother board 5630 respectively.

A PC card 5621 shown in FIG. 19C is an example of a processing board including a CPU, GPU, storage device, and the like. The PC card 5621 has a board 5622 . In addition, the board 5622 has a connection terminal 5623 , a connection terminal 5624 , a connection terminal 5625 , a semiconductor device 5626 , a semiconductor device 5627 , a semiconductor device 5628 , and a connection terminal 5629 . Note that FIG. 19C illustrates semiconductor devices other than the semiconductor devices 5626, 5627, and 5628; The description of the semiconductor device 5628 may be referred to.

The connection terminal 5629 has a shape that can be inserted into the slot 5631 of the mother board 5630 , and the connection terminal 5629 functions as an interface for connecting the PC card 5621 and the mother board 5630 . Examples of standards for the connection terminal 5629 include PCIe.

The connection terminals 5623 , 5624 , and 5625 can be interfaces for power supply and signal input to the PC card 5621 , for example. Also, for example, an interface for outputting a signal calculated by the PC card 5621 can be used. Standards for the connection terminals 5623, 5624, and 5625 include, for example, USB (Universal Serial Bus), SATA (Serial ATA), and SCSI (Small Computer System Interface). When video signals are output from the connection terminal 5623, the connection terminal 5624, and the connection terminal 5625, respective standards include HDMI (registered trademark).

The semiconductor device 5626 has terminals (not shown) for inputting and outputting signals. By inserting the terminals into sockets (not shown) provided on the board 5622, the semiconductor device 5626 and the board 5622 are connected. can be electrically connected.

The semiconductor device 5627 has a plurality of terminals, and the terminals are electrically connected to the wiring of the board 5622 by, for example, reflow soldering. be able to. Examples of the semiconductor device 5627 include FPGA (Field Programmable Gate Array), GPU, and CPU. As the semiconductor device 5627, the electronic component 730 can be used, for example.

The semiconductor device 5628 has a plurality of terminals, and the terminals are electrically connected to the wiring of the board 5622 by, for example, reflow soldering. be able to. Examples of the semiconductor device 5628 include a memory device. As the semiconductor device 5628, the electronic component 700 can be used, for example.

Computer 5600 can also function as a parallel computer. By using the computer 5600 as a parallel computer, for example, large-scale calculations required for learning and inference of artificial intelligence can be performed.

By using the memory device of one embodiment of the present invention in the various electronic devices described above, the electronic devices can be made smaller and consume less power. Further, since the memory device of one embodiment of the present invention consumes less power, heat generation from the circuit can be reduced. Therefore, adverse effects on the circuit itself, peripheral circuits, and modules due to the heat generation can be reduced. Further, by using the memory device of one embodiment of the present invention, an electronic device that operates stably even in a high-temperature environment can be realized. Therefore, the reliability of electronic equipment can be improved.

This embodiment can be appropriately combined with other embodiments and the like described in this specification.

10: memory cell, 15: memory array, 100: storage device, 150: capacitive element, 153: insulator, 154: insulator, 158: opening, 160: conductor, 200: transistor

Claims (5)

1. N storage layers (N is an integer equal to or greater than 2);
   a plurality of first wirings extending in a first direction that is a stacking direction of the N memory layers;
   a plurality of second wirings extending in the first direction;
   a plurality of third wirings extending in a second direction intersecting with the first direction;
   a plurality of fourth wirings extending in the second direction;
   each of the N storage layers has a plurality of memory cells arranged in a matrix;
   each of the plurality of memory cells has a first transistor, a second transistor, and a capacitive element;
   a gate of the first transistor electrically connected to one of the plurality of third wirings;
   one of the source and the drain of the first transistor is electrically connected to one of the plurality of first wirings via a first conductor;
   one electrode of the capacitive element is electrically connected to one of the plurality of fourth wirings;
   one electrode of the capacitive element is electrically connected to the other of the source or drain of the first transistor and the gate of the second transistor;
   one of the source and the drain of the second transistor is electrically connected to one of the plurality of first wirings;
   the other of the source and the drain of the second transistor is electrically connected to one of the plurality of second wirings;
   The first conductor has a region in which at least one of a top surface, a side surface, and a bottom surface is in contact with one of the plurality of first wirings.
2. In claim 1,
   one of the source and the drain of the second transistor is electrically connected to one of the plurality of first wirings via a second conductor;
   The second conductor has a region in which at least one of a top surface, a side surface, and a bottom surface is in contact with one of the plurality of second wirings.
3. In claim 1 or claim 2,
   the other of the source and the drain of the second transistor is electrically connected to one of the plurality of second wirings via a third conductor;
   The third conductor has a region in which at least one of a top surface, a side surface, and a bottom surface is in contact with one of the plurality of second wirings.
4. In claim 1 or claim 2,
   A memory device in which the first transistor has a back gate.
5. In claim 1 or claim 2,
   A memory device in which the first transistor includes an oxide semiconductor.

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