JP2011091329A - Resistance random access memory element, resistance random access memory, and method of controlling the resistance random access memory element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resistance random access memory element achieving small variations in switching characteristics and suitable for high integration, and to provide a method of controlling the resistance random access memory element. <P>SOLUTION: The resistance random access memory element 20 includes: a variable resistance film having a titanium oxide film 2 and a zirconium oxide film 3; a first electrode 1 formed under the titanium oxide film 2; and a second electrode 4 formed on the zirconium oxide film 3. The titanium oxide film 2, a crystal grain of which easily grows larger, can be thinned, and the microcrystalline zirconium oxide film 3 is flat, thereby the surface irregularities of a zirconium oxide/titanium oxide laminated film can be reduced. When the resistance random access memory element is miniaturized, variations in electrical characteristics due to the surface irregularities of the variable resistance film can be reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a resistance change type memory element, a resistance change type nonvolatile memory, and a resistance change type memory element control method, and in particular, a resistance change type in which a resistance change film made of an insulating material is sandwiched between two electrodes. The present invention relates to a memory element, a resistance variable nonvolatile memory having such a resistance variable memory element in a memory cell, and a resistance variable memory element control method.

  Research on non-volatile memories such as flash memories, ferroelectric memories (FeRAM: Ferroelectric Random Access Memory), MRAM (Magnetic RAM), and OUM (Ovonic Unified Memory) has been actively conducted.

  In addition to these conventional nonvolatile memories, Non-Patent Document 1 proposes a variable resistance nonvolatile memory (ReRAM: Resistance RAM). The resistance change nonvolatile memory described in Non-Patent Document 1 can write information and read information nondestructively by setting the resistance value of the resistance change film of the memory cell by applying a voltage pulse.

  FIG. 7 is a cross-sectional view schematically showing the structure of the resistance change type memory element 120. In the resistance change memory element 120, a resistance change film 117 is formed on the lower electrode 101, and an upper electrode 104 is formed on the resistance change film 117. The resistance change type memory element 120 has an advantage that it has a smaller cell area and can be multi-valued than a conventional nonvolatile memory.

In Non-Patent Document 1, PCMO (Pr _0.7 Ca _0.3 MnO ₃ ) or YBCO (YBa ₂ Cu ₃ O _y ) is used as the resistance change film 117.

Other proposals have been made for variable resistance nonvolatile memories (Non-Patent Document 2 and Non-Patent Document 3). In Non-Patent Document 2, polycrystalline NiO _x (x = 1 to 1.5) of about 50 nm is used as the resistance change film 117. In addition, it is described that when a positive voltage is applied to the upper electrode 104, the state changes to a low resistance state or a high resistance state.

In Non-Patent Document 3, 80 nm microcrystalline TiO ₂ is used for the resistance change film 117. Two control methods are described. The first control method is a method of reducing the resistance by applying a negative (or positive) voltage to the upper electrode 104 and increasing the resistance by applying a positive (or negative) voltage (bipolar operation). On the other hand, the second control method is a method (unipolar operation) in which the resistance is reduced and the resistance is increased only by applying a positive (negative) voltage.

The switching mechanism of ReRAM using TiO ₂ as the resistance change film 117 is considered as follows. According to Non-Patent Document 4, first, a filament is formed in TiO ₂ by first high voltage application (referred to as “forming”), and a switching operation occurs due to a change in the resistance of the filament.

  Switching from a low resistance state to a high resistance state (reset) occurs when either a positive or negative voltage is applied to the upper electrode 104, and when a positive voltage is applied to the upper electrode 104, the upper part of the filament. When the vicinity of the electrode 104 is increased in resistance and a negative voltage is applied to the upper electrode 104, the vicinity of the lower electrode 101 of the filament is increased in resistance (Non-Patent Document 5). Therefore, a candidate for the switching mechanism of ReRAM is anodic oxidation of the filament.

W.W.Zhuang et.al., 2002 IEDM, paper number 7.5, Dec. 2002 G.-S. Park et.al., APL, Vol. 91, pp.222103, 2007 C. Yoshida et.al., APL, Vol. 91, pp.223510, 2007 K. Kinoshita et.al., JJAP, Vol. 45, No. 37. L911, 2006 K. Kinoshita et.al., APL, Vol. 89, pp.103589, 2006

  The analysis according to the invention is given below.

  As in Non-Patent Documents 1 to 3, when the resistance change memory element 120 is miniaturized while using a polycrystalline or microcrystalline material for the resistance change film 117, the size of the crystal grains is larger than the element size. It cannot be ignored. In particular, there is a problem that variation in electrical characteristics between elements increases due to unevenness of the surface of the resistance change film 117 due to crystal grains.

  Unevenness can be suppressed by reducing the thickness of the resistance change film 117. However, when the resistance change film 117 is thinned, the leakage current is greatly increased and the switching operation cannot be obtained. Therefore, a thick variable resistance film 117 of 50 nm or more is used.

  The characteristics of the resistance change film 117 are easily affected by process damage during device formation. In particular, the upper portion of the resistance change film 117 is easily damaged when the upper electrode 104 is deposited. When the resistance change film 117 is damaged, the yield of the resistance change memory element 120 is lowered.

  Therefore, it is a problem to realize a resistance change type memory element that has a small variation in switching characteristics and is suitable for high integration. An object of the present invention is to provide a resistance change type memory element and a control method therefor that solve such a problem.

The resistance change type memory element according to the first aspect of the present invention provides:
A resistance change film having a titanium oxide film and a zirconium oxide film;
A first electrode formed on the titanium oxide film;
And a second electrode formed on the zirconium oxide film.

The resistance change type memory element control method according to the second aspect of the present invention includes:
A resistance change type memory element control method in which a resistance change film having a titanium oxide film and a zirconium oxide film is provided between a first electrode and a second electrode,
Applying a forming voltage between the first electrode and the second electrode to reduce a resistance value between the first electrode and the second electrode.

The resistance change type memory element control method according to the third aspect of the present invention includes:
A resistance change type comprising a resistance change film having a titanium oxide film and a zirconium oxide film, a first electrode formed on the titanium oxide film, and a second electrode formed on the zirconium oxide film A method for controlling a memory element, comprising:
Applying a positive reset voltage to the second electrode to increase a resistance value between the first electrode and the second electrode;
Applying a positive set voltage higher than the reset voltage to the second electrode to reduce a resistance value between the first electrode and the second electrode.

  According to the resistance change type memory element and the control method thereof according to the present invention, it is possible to realize a resistance change type memory element suitable for high integration with small variation in switching characteristics.

1 is a cross-sectional view schematically showing a configuration of a resistance change memory element according to a first embodiment of the present invention. It is sectional drawing which shows typically the structure of the resistance change memory element which concerns on the 2nd Embodiment of this invention. It is a figure which shows the measurement result of the XPS spectrum of the zirconium oxide film | membrane in the resistance change memory element which concerns on the 2nd Embodiment of this invention. It is a figure which shows the switching characteristic of the resistance change memory element which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the memory cell of the resistance variable nonvolatile memory which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the memory cell of the resistance variable nonvolatile memory which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows typically the structure of the conventional resistance change type memory element.

  The resistance change type memory element of the first development form is preferably the resistance change type memory element according to the first aspect.

  In the resistance change type memory element according to the second development form, the zirconium oxide film may be formed on the titanium oxide film.

  In the resistance change memory element according to the third development mode, the resistance change film may further include a film made of an oxide of zirconium and titanium between the zirconium oxide film and the titanium oxide film. .

  In the resistance change type memory element according to the fourth development mode, it is preferable that the titanium oxide film is thinner than the zirconium oxide film.

  In the resistance change type memory element of the fifth development form, the oxygen concentration of the titanium oxide film has a maximum value at the interface between zirconium oxide and titanium oxide, and decreases toward the first electrode. preferable.

  In the resistance change type memory element according to a sixth development, the titanium oxide film preferably contains nitrogen.

  In the resistance change memory element according to the seventh development mode, it is preferable that the concentration of nitrogen contained in the titanium oxide film increases toward the first electrode.

  In the resistance-change memory element according to the eighth development, it is preferable that the first electrode is made of titanium nitride.

  In the resistance change type memory element according to the ninth development mode, the concentration of nitrogen contained in the titanium oxide film increases from the interface between the zirconium oxide film and the titanium oxide film toward the first electrode. Is preferred.

  In the resistance change memory element according to the tenth development, it is preferable that the first electrode includes at least one of ruthenium, platinum, tantalum, tungsten, titanium, and nickel.

  In the resistance change memory element according to the eleventh development, it is preferable that the zirconium oxide film contains a metal other than zirconium.

  In the resistance change memory element according to the twelfth development mode, the zirconium oxide film may contain aluminum.

  The resistance change nonvolatile memory according to the thirteenth embodiment preferably includes the resistance change memory element in each memory cell.

  It is preferable that the variable resistance nonvolatile memory according to the fourteenth embodiment further includes a transistor for controlling the variable resistance memory element in each memory cell.

  The resistance change type memory element control method according to the fifteenth embodiment is preferably the resistance change type memory element control method according to the second aspect.

  The resistance change type memory element control method according to the sixteenth embodiment is preferably the resistance change type memory element control method according to the third aspect.

  According to the resistance change type memory element and the control method thereof according to the present invention, it is possible to realize a resistance change type memory element suitable for high integration with small variation in switching characteristics.

(Embodiment 1)
A resistance-change memory element according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the configuration of the resistance change memory element 20 according to the present embodiment. Referring to FIG. 1, the resistance change memory element 20 includes a lower electrode 1, a titanium oxide film 2, a zirconium oxide film 3, and an upper electrode 4.

  The resistance change type memory element 20 of this embodiment has an MIM structure (Metal / Insulator / Metal) in which an insulating film (resistance change film) is sandwiched between an upper electrode 4 and a lower electrode 1. The insulating film has a laminated structure of the zirconium oxide film 3 and the titanium oxide film 2. The titanium oxide film 2 having large crystal grains that are easy to grow can be thinned, and the microcrystalline zirconium oxide film 3 is flat, so that unevenness on the surface of the zirconium oxide / titanium oxide laminated film can be reduced.

  According to the resistance change type memory element 20 of this embodiment, when the resistance change type memory element is miniaturized, it is possible to reduce variation in electrical characteristics between elements due to the unevenness of the resistance change film surface.

  In the resistance change type memory element 20 of the present embodiment, it is necessary to apply a predetermined voltage between the upper and lower electrodes to form a low resistance switching path in the zirconium oxide film 3. As described above, since the zirconium oxide film 3 is a homogeneous microcrystalline film, a switching path with little variation between elements can be formed.

  In the resistance change type memory element 20 of the present embodiment, a positive voltage (reset voltage) is applied to the upper electrode 4 on the side in contact with the zirconium oxide film 3 so that the resistance value between the upper electrode 4 and the lower electrode 1 is increased. The resistance value between the upper electrode 4 and the lower electrode 1 is lowered by applying a positive voltage (set voltage) higher than the reset voltage to the upper electrode 4 on the side in contact with the zirconium oxide film 3. At this time, both high resistance and low resistance switching can be performed with only one polarity (for example, positive) voltage, and the circuit scale can be reduced. Therefore, the resistance change type memory element 20 of this embodiment is suitable for high integration.

  As described above, according to the resistance change type memory element 20 of the present embodiment, a resistance change type memory element that is advantageous for high integration, has little variation, and has stable electric characteristics can be realized.

(Embodiment 2)
A resistance change type memory element according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view schematically showing the configuration of the resistance change memory element 30 according to this embodiment. Referring to FIG. 2, the resistance change memory element 30 includes a lower electrode 21, a titanium oxide film 22, a zirconium oxide film 23, and an upper electrode 24. The resistance change type memory element of this embodiment has an MIM structure (Metal / Insulator / Metal) in which two insulating films (resistance change films) are sandwiched between a lower electrode 21 and an upper electrode 24. The first insulating film is a titanium oxide film 22, and the second insulating film is a zirconium oxide film 23.

  The titanium oxide film 22 is preferably formed between the lower electrode 21 and the zirconium oxide film 23. However, the titanium oxide film 22 may be formed between the upper electrode 24 and the zirconium oxide film 3. In the present embodiment, it is assumed that the titanium oxide film 22 is formed between the lower electrode 21 and the zirconium oxide film 23.

  The titanium oxide film 22 is preferably thinner than the zirconium oxide film 23. Here, as an example, the thickness of the zirconium oxide film 23 is 12 nm, and the thickness of the titanium oxide film 22 is 3 nm.

  Further, it is desirable to form an intermediate layer made of an oxide of titanium and zirconium between the titanium oxide film 22 and the zirconium oxide film 23. As will be described later, switching to higher resistance occurs mainly at the interface between zirconium oxide and titanium oxide. Zirconium oxide has the property of being further stabilized by adding a metal having a lower valence than zirconium. Therefore, by forming an intermediate layer containing titanium that can have a lower valence than zirconium, a high resistance state can be obtained. Reliability is improved. Even if aluminum is added to the zirconium oxide film 23, the same effect can be obtained.

  Furthermore, it is preferable that the oxygen concentration of the titanium oxide film 22 has a maximum value at the interface between zirconium oxide and titanium oxide, and the oxygen concentration decreases toward the lower electrode 21. By using such a structure, oxygen ions can easily move from the vicinity of several electrodes when a switching voltage is applied, and switching endurance resistance is improved.

  Even if the zirconium oxide film 23 is a single layer, it functions as a resistance change memory element. However, in this case, the yield is 50% or less. On the other hand, since the titanium oxide film 22 used in this embodiment is too thin, the single layer does not function as a resistance change memory element.

  The inventors of the present invention have found based on experiments that it functions as a high-resistance variable resistance memory element only when the zirconium oxide film 23 and the thin titanium oxide film 22 are stacked.

  The lower electrode 21 may basically have conductivity. The lower electrode 21 is, for example, Au, Ni, Co, Pt, Ru, Ir, Ti, Cu, Ta, iridium-tantalum alloy (Ir-Ta), tin-added indium oxide (ITO), an alloy thereof, or These oxides, nitrides, fluorides, carbides or silicides can be used. The lower electrode 21 may be a laminate of these materials. Here, as an example, Ru is used for the lower electrode 21.

  The upper electrode 24 may basically have conductivity. The upper electrode 24 is made of, for example, Au, Ni, Co, Pt, Ru, Ir, Ti, Cu, Ta, iridium-tantalum alloy (Ir-Ta), tin-doped indium oxide (ITO), an alloy thereof, or These oxides, nitrides, fluorides, carbides or silicides can be used. Further, the upper electrode 24 may be a laminate of these materials. Here, as an example, Pt is used for the upper electrode 24.

  In the MIM structure included in the resistance change memory element 30, adjacent layers may be stacked in at least some of these regions.

  In the resistance change memory element 30, a voltage is applied between the upper and lower electrodes to form a low-resistance conduction path between the upper and lower electrodes.

  After performing an operation of forming a low-resistance conductive path between the upper and lower electrodes (forming), a predetermined positive voltage is applied to the upper electrode 24 in contact with the zirconium oxide film 23 (reset voltage), so that the low resistance state is reached. By switching to the high resistance state and applying a positive voltage (set voltage) higher than the reset voltage to the upper electrode 24 in contact with the zirconium oxide film 23, the resistance value is switched from the high resistance state to the low resistance state. Can be held.

  Hereinafter, based on the experimental results, it is shown that the stable function of the resistance change memory element is exhibited by laminating the zirconium oxide film 23 and the titanium oxide film 22.

  For comparison, three types of samples (Sample 1 to Sample 3) as shown in Table 1 were prepared. Sample 3 is the resistance change type memory element 30 of the present embodiment.

  The variable resistance film of Sample 1 is a 17 nm titanium oxide single layer. The resistance change film of Sample 2 is a 12 nm zirconium oxide single layer. The resistance change film of Sample 3 has a laminated structure of 3 mm titanium oxide and 12 nm zirconium oxide.

  First, Ru of 20 nm was continuously formed on a semiconductor substrate using a DC sputtering apparatus at room temperature to form the lower electrode 21.

  Subsequently, titanium was deposited by a DC sputtering apparatus, and titanium was plasma-oxidized to form a 3 nm titanium oxide film 22 (Sample 3). Since the titanium oxide film of Sample 1 was thick, it was formed by reactive sputtering. For sample 2, the titanium oxide film 22 was not formed.

  Next, a zirconium oxide film 23 was formed using an ALD (Atomic Layer Deposition) apparatus. ZDEAZ (tetrakisdiethylaminozirconium) was used as a raw material, and ZDEAZ and oxygen were alternately supplied at a substrate temperature of 140 ° C. For sample 1, the zirconium oxide film 23 was not formed.

  The composition of the deposited zirconium oxide film 23 was evaluated using XPS (X-ray Photoemission Spectroscopy). FIG. 3 shows XPS spectra of O1s orbitals (525 to 535 eV) and Zr3d orbitals (174 to 194 eV). Here, Al (kα) rays were used as the X-ray source.

  The composition ratio (O / Zr) of the zirconium oxide film 23 obtained from the peak area of the XPS spectrum is 2, and it can be seen that a substantially stoichiometric zirconium oxide film 23 is formed.

  After the zirconium oxide film was formed, Pt was formed using an electron gun vapor deposition method to form the upper electrode 24. At this time, a pattern of the upper electrode 24 was formed using a stencil mask.

  The initial leakage current and switching characteristics between the upper and lower electrodes of Samples 1 to 3 prepared as described above were evaluated. The evaluated electrode shape is 25 μm square.

  After applying a positive bias to the lower electrode 1 to lower the resistance of the insulating film (hereinafter referred to as “forming”), the switching characteristics were evaluated. By the forming process, a current path (switching path) is formed in the insulating film of the MIM, and a switching phenomenon occurs in the current path. In the case of Sample 3 having a laminated structure (resistance change type memory element 30 of the present embodiment), the resistance value in the low resistance state is lower than the resistance value in the initial state, and therefore switching in the zirconium oxide / titanium oxide laminated film is performed. It was found that a path was formed from the titanium oxide film 2 through the zirconium oxide.

As a result of evaluating the switching characteristics, Sample 1 having a TiO ₂ single layer film had a very large initial leakage current even in the case of a thick film of 17 nm, and did not show the switching characteristics. On the other hand, Sample 2 having a single layer of zirconium oxide had a small initial leakage current and showed switching characteristics, but only a yield of 50% was obtained. However, in the sample 3 having the laminated film of the zirconium oxide film 23 and the titanium oxide film 22, although the thickness of the titanium oxide film 22 is as thin as 3 nm, the initial leakage current is small and a yield of 80% or more is obtained. It was.

  FIG. 4 is a diagram showing switching characteristics of the resistance change type memory element 30 (sample 3) of the present embodiment.

  Switching from the low resistance state to the high resistance state was performed by applying a positive bias (reset voltage) to the upper electrode 24 side in contact with the zirconium oxide film 23. The switching mechanism to the high resistance state is that oxygen ions (O−) diffuse in the direction of the upper electrode 24 in contact with the zirconium oxide film 23 by the electric field in the zirconium oxide / titanium oxide laminated film, and at the zirconium oxide / titanium oxide interface. It is thought that the oxidation reaction of the switching path occurs.

  As described above, the phenomenon of resistance change occurs at the zirconium oxide / titanium oxide interface along the switching path. Therefore, when the thin titanium oxide film 22 is provided in the lower part and the thick zirconium oxide film 23 is provided in the upper part, the interface of the laminated film becomes less susceptible to sputtering damage during the formation of the upper electrode 24, and the yield is improved. To do.

  From the above experimental results, it was shown that the function of the resistance change memory element is exhibited at a high yield by using a laminated film of the zirconium oxide film 23 and the titanium oxide film 22 as the insulating film having the MIM structure.

  According to the resistance change film of the resistance change type memory element 30 of the present embodiment, the titanium oxide film 22 in which crystal grains easily grow can be thinned, and the microcrystalline zirconium oxide film 23 is flat. Unevenness on the surface of the titanium laminated film can be reduced.

  Therefore, according to the resistance change type memory element 30 of this embodiment, even when the element is miniaturized, it is possible to suppress variations in electrical characteristics between elements due to the unevenness of the surface of the resistance change film.

  In the resistance change memory element 30, it is necessary to apply a predetermined voltage between the upper and lower electrodes (forming voltage) and form a switching path so as to penetrate the zirconium oxide film 23 and the titanium oxide film 22. There is. However, according to the resistance change type memory element 30 of this embodiment, since the zirconium oxide film 23 is a homogeneous microcrystal, a switching path with little variation between elements can be formed. Further, according to the resistance change type memory element 30 of the present embodiment, the zirconium oxide film 23 functions as a process damage mitigating layer, so that the yield of the element can be improved.

(Embodiment 3)
A variable resistance nonvolatile memory (ReRAM) according to a third embodiment of the present invention will be described with reference to the drawings. The ReRAM of this embodiment is a 1T1R (one transistor and one resistance) type ReRAM, and includes the memory cell 50 shown in FIG. FIG. 5 is a diagram showing the structure of the memory cell 50. Referring to FIG. 5, a memory cell 50 includes a semiconductor substrate 15, a gate insulating film 16, a gate electrode 5, a source (or drain) 6, a drain (or source) 7, vias 8 to 10, wiring layers 11, 12, and A resistance-change memory element 20 is included. The resistance change memory element 20 includes a lower electrode 1, a titanium oxide film 2, a zirconium oxide film 3, and an upper electrode 4.

  Referring to FIG. 5, a control transistor including a gate insulating film 16, a gate electrode 5, a source (or drain) 6, and a drain (or source) 7 is formed on a semiconductor substrate 15. A via 8 is formed so as to be connected to the drain 7. Further, an MIM structure is formed in which a lower electrode 1, an insulating film composed of a titanium oxide film 2 and a zirconium oxide film 3, and an upper electrode 4 are sequentially stacked so as to be connected to the via 8. A via 10 is formed on the upper electrode 4, and a second wiring layer 12 (wiring patterned in the wiring layer) is formed so as to be connected to the via 10. On the other hand, a via 9 is formed so as to connect to the source 6. A first wiring layer 11 (wiring patterned in the wiring layer) is formed so as to be connected to the via 9.

  The control transistor may be an n-type field effect transistor (n-type FET) or a p-type field effect transistor (p-type FET). In the present embodiment, as an example, an n-type FET is used as a control transistor.

  For example, an oxide film can be used as the gate insulating film 16. However, the gate insulating film 16 may be a hafnium oxide film, a zirconium oxide film, alumina, or a silicate, nitride, or laminated film thereof.

  In this embodiment, polysilicon to which phosphorus is added is used as the gate electrode 5. However, the gate electrode 5 may be a metal gate or a silicide gate.

  The lower electrode 1 may basically have conductivity. The lower electrode 1 is made of, for example, Au, Ni, Co, Pt, Ru, Ir, Ti, Cu, Ta, iridium-tantalum alloy (Ir-Ta), tin-doped indium oxide (ITO), an alloy thereof, or These oxides, nitrides, fluorides, carbides or silicides can be used. The lower electrode 1 may be a laminate of these materials. In the present embodiment, TiN is used for the lower electrode 1 as an example.

  The upper electrode 4 may basically have conductivity. The upper electrode 4 is made of, for example, Au, Ni, Co, Pt, Ru, Ir, Ti, Cu, Ta, iridium-tantalum alloy (Ir-Ta), tin-doped indium oxide (ITO), an alloy thereof, or These oxides, nitrides, fluorides, carbides or silicides can be used. Further, the upper electrode 4 may be a laminate of these materials. In the present embodiment, Ru is used for the upper electrode 4 as an example.

  Both the titanium oxide 2 and the zirconium oxide 3 that are insulating films (resistance change films) may be provided on the upper side. However, since the portion where the resistance changes is the titanium oxide / zirconium oxide interface, it is preferable to provide the thin titanium oxide 2 on the lower side in order to reduce the influence of sputtering damage during the formation of the upper electrode 4.

  In the present embodiment, a structure in which 3 nm of titanium oxide is deposited by plasma-oxidizing TiN as the lower electrode 1 and 12 nm of zirconium oxide is continuously deposited is used. Since the lower electrode 1 is directly oxidized to form the titanium oxide film 2, the titanium oxide film 2 contains nitrogen. Further, the oxygen concentration of the titanium oxide film 2 reaches a maximum value at the interface between zirconium oxide and titanium oxide and decreases toward the lower electrode 1. On the other hand, the nitrogen concentration of the titanium oxide film 2 increases toward the lower electrode 1.

  Conversely, since the oxygen concentration decreases toward the electrode, the oxygen defect concentration increases toward the electrode. Therefore, when a positive voltage is applied to the upper electrode 4, oxygen ions easily move in the direction of the zirconium oxide / titanium oxide interface. Therefore, the endurance tolerance of switching is improved. Further, nitrogen in the titanium oxide has an effect of improving the thermal stability of the oxygen profile of the titanium oxide film 2.

  Next, a method for controlling the ReRAM according to the present embodiment will be described. First, in order to perform forming, a positive voltage is applied to the wiring layer 11 and the gate electrode 5 to reduce the resistance of the insulating film (resistance change film). At this time, the voltage applied to the gate electrode 5 is adjusted so that the current is limited by the control transistor so that the insulating film (resistance change film) has a desired resistance value. Note that a positive voltage may be applied to the wiring layer 12 instead of the first wiring layer 11 during forming.

  When switching from the low resistance state to the high resistance state, a positive voltage is applied to the wiring layer 12 and the gate electrode 5 (reset voltage).

  At the time of switching from the high resistance state to the low resistance state, a positive voltage is applied to the wiring layer 12 and the gate electrode 5 (set voltage). At this time, a higher voltage is applied to the wiring layer 12 than when switching to the high resistance state. Further, the voltage applied to the gate electrode 5 is adjusted so that the current is limited by the control transistor so that the resistance change film has a desired resistance value.

(Embodiment 4)
A variable resistance nonvolatile memory (ReRAM) manufacturing method according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a diagram for explaining the method of manufacturing the ReRAM. Here, a manufacturing method of the memory cell 50 (FIG. 4) of the 1T1R type ReRAM according to the third embodiment will be described.

  First, as shown in FIG. 6A, a gate insulating film 16 and phosphorus-added polysilicon 5 are deposited on a semiconductor substrate 15 and patterned using an exposure process and a dry etching process to form a gate electrode 5. .

Next, as shown in FIG. 6B, using the gate electrode 5 as a mask, phosphorus implantation with a dose of 2E + 15 cm ⁻² is performed to form a source (or drain) 6 and a drain (or source) 7 region.

  Next, as shown in FIG. 6C, a first interlayer insulating film 13 is deposited on the entire surface of the semiconductor substrate 15, and the surface is planarized by using a CMP (Chemical Mechanical Polishing) method. In the present embodiment, an oxide film is used as the first interlayer insulating film 13.

  Next, as shown in FIG. 6D, vias are opened in the first interlayer insulating film 13 using an exposure process and a dry etching process, and TiN and W are deposited. The surface is flattened using the CMP method, and TiN and W other than the via portion are removed to form the via 8.

  Next, as shown in FIG. 6E, 20 nm of TiN is deposited, and the surface of TiN is plasma-oxidized to form a 3 nm of titanium oxide film 2. Thereafter, a 12 nm zirconium oxide film 3 and a 20 nm Ru (upper electrode 4) are sequentially deposited, and the lower electrode 1 and the insulating film (resistance change film) (that is, the titanium oxide film 2 and the An MIM structure composed of the zirconium oxide film 3) and the upper electrode 4 is formed. DC sputtering is used to deposit TiN and Ru. The ALD method was used for the deposition of the zirconium oxide film 3. ZDEAZ (tetrakisdiethylaminozirconium) was used as a raw material for zirconium oxide, and ZDEAZ and oxygen were alternately supplied at a substrate temperature of 140 ° C. to form the zirconium oxide film 3.

  Next, as shown in FIG. 6F, an interlayer insulating film 14 is deposited on the entire surface of the semiconductor substrate 15, and the surface is planarized by using a CMP method. In this embodiment, an oxide film is used as the interlayer insulating film 14.

  Next, as shown in FIG. 6G, vias are opened in the interlayer insulating film 14 and the interlayer insulating film 13 using an exposure process and a dry etching process, and TiN and W are deposited. The surface is planarized using CMP, and TiN and W other than the via portion are removed to form vias 9 and 10.

  TiN and Al are sequentially deposited on the interlayer insulating film 14 to form a metal interconnect layer, and patterning is performed using an exposure process and a dry etching process, thereby forming wiring layers 11 and 12. .

  According to the present embodiment, the MIM element (resistance change memory element 20) of the resistance change nonvolatile memory (ReRAM) is connected to the drain 7 of the control transistor. Therefore, when the forming voltage is applied and when switching from high resistance to low resistance, the current can be controlled by the gate electrode 5 of the transistor, and a switching operation with little variation can be realized. In addition, since the lower electrode 1 is directly oxidized to form the titanium oxide film 2, the number of process steps is reduced, and the manufacturing cost of the ReRAM can be reduced.

  Each disclosure of the above non-patent document is incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiment can be changed and adjusted based on the basic technical concept. Various combinations and selections of various disclosed elements are possible within the scope of the claims of the present invention. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

1, 21, 101 Lower electrode 2, 22 Titanium oxide film 3, 23 Zirconium oxide film 4, 24, 104 Upper electrode 5 Gate electrode 6 Source 7 Drain 8-10 Via 11, 11 Wiring layer 13, 14 Interlayer insulating film 15 Semiconductor Substrate 16 Gate insulating film 20, 30, 120 Resistance change memory element 50 Memory cell 117 Resistance change film

Claims (16)

A resistance change film having a titanium oxide film and a zirconium oxide film;
A first electrode formed on the titanium oxide film;
A resistance change memory element, comprising: a second electrode formed on the zirconium oxide film.   The resistance variable memory element according to claim 1, wherein the zirconium oxide film is formed on the titanium oxide film.   The resistance variable memory element according to claim 1, wherein the resistance change film further includes a film made of an oxide of zirconium and titanium between the zirconium oxide film and the titanium oxide film.   4. The resistance change type memory element according to claim 1, wherein a thickness of the titanium oxide film is smaller than a thickness of the zirconium oxide film. 5.   5. The oxygen concentration of the titanium oxide film has a maximum value at an interface between zirconium oxide and titanium oxide, and decreases toward the first electrode. 6. The resistance change type memory element according to item.   The resistance change memory element according to claim 1, wherein the titanium oxide film contains nitrogen.   The resistance change type memory element according to claim 6, wherein the concentration of nitrogen contained in the titanium oxide film increases toward the first electrode.   The resistance change type memory device according to claim 1, wherein the first electrode is made of titanium nitride.   9. The resistance change according to claim 8, wherein a concentration of nitrogen contained in the titanium oxide film increases from an interface between the zirconium oxide film and the titanium oxide film toward the first electrode. Type memory device.   8. The variable resistance memory element according to claim 1, wherein the first electrode includes at least one of ruthenium, platinum, tantalum, tungsten, titanium, and nickel. 9. .   The resistance change type memory element according to claim 1, wherein the zirconium oxide film contains a metal other than zirconium.   The resistance change type memory device according to claim 11, wherein the zirconium oxide film contains aluminum.   A variable resistance nonvolatile memory comprising the variable resistance memory element according to any one of claims 1 to 12 in each memory cell.   14. The variable resistance nonvolatile memory according to claim 13, further comprising a transistor for controlling the variable resistance memory element in each memory cell. A resistance change type memory element control method in which a resistance change film having a titanium oxide film and a zirconium oxide film is provided between a first electrode and a second electrode,
Including a step of applying a forming voltage between the first electrode and the second electrode to reduce a resistance value between the first electrode and the second electrode. Resistance variable memory element control method. A resistance change type comprising a resistance change film having a titanium oxide film and a zirconium oxide film, a first electrode formed on the titanium oxide film, and a second electrode formed on the zirconium oxide film A method for controlling a memory element, comprising:
Applying a positive reset voltage to the second electrode to increase a resistance value between the first electrode and the second electrode;
Applying a positive set voltage higher than the reset voltage to the second electrode to reduce a resistance value between the first electrode and the second electrode. , A resistance change type memory element control method.

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