KR20070063816A - Phase change ram device and method of manufacturing the same - Google Patents

Abstract

A phase change memory device and its manufacturing method are provided to reduce remarkably a write current necessary for a phase change by using a plug type phase change layer. A first interlayer dielectric(31) is formed on a semiconductor substrate(30) with a lower pattern. A contact plug(34) is formed in the first interlayer dielectric. A lower electrode(35) is formed on the first interlayer dielectric including the contact plug. A second interlayer dielectric(36) is formed on the first interlayer dielectric to cover the lower electrode. A phase change layer(38) is formed in the second interlayer dielectric to contact an edge portion of the lower electrode. The phase change layer is formed like a plug type structure. An upper electrode(39) is formed on the second interlayer dielectric.

Description

Phase change RAM device and method of manufacturing the same

1 is a cross-sectional view showing a conventional phase change memory element.

2 is a graph for explaining the amount of reset current according to the contact size in the phase change memory device.

3A to 3G are cross-sectional views of processes for describing a method of manufacturing a phase change memory device according to an embodiment of the present invention.

4 is a cross-sectional view illustrating a method of manufacturing a phase change memory device according to another embodiment of the present invention.

5 is a cross-sectional view for explaining a method of manufacturing a phase change memory device according to still another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

30 semiconductor substrate 31 first interlayer insulating film

32: nitride film 33: first contact hole

34: contact plug 35: lower electrode

36: second interlayer insulating film 37: second contact hole

38 phase change film 39 upper electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change memory element, and more particularly, to a phase change memory element capable of lowering a write current and a manufacturing method thereof.

The memory device is a volatile random access memory (RAM) device that loses input information when the power is cut off, and a read only memory (ROM) device that maintains the storage state of the input information even when the power is cut off. It is largely divided. The volatile RAM devices may include DRAM and SRAM, and the nonvolatile ROM devices may include flash memory devices such as EEPROM (Elecrtically Erasable and Programmable ROM). have.

However, although the DRAM has a very good memory device as is well known, high charge storage capability is required, and for this purpose, it is difficult to achieve high integration since the electrode surface area must be increased. In addition, the flash memory device requires a high operating voltage compared to a power supply voltage in connection with a structure in which two gates are stacked, and thus requires a separate boost circuit to form a voltage required for write and erase operations. Therefore, there is a difficulty in high integration.

Accordingly, many studies are being conducted to develop new memory devices having characteristics of the nonvolatile memory device and having a simple structure. For example, recently, a phase change RAM device has been developed. Was proposed.

The phase change memory device utilizes a difference in resistance between crystalline and amorphous phases due to the phase change of the phase conversion film interposed between the electrodes from the crystal state to the amorphous state through the current flow between the lower electrode and the upper electrode. It is a storage element for determining stored information. In other words, the phase-conversion memory device uses a chalcogenide film as a phase conversion film. The chalcogenide film is a compound film composed of germanium (Ge), stevidium (Sb), and tellurium (Te). The phase change occurs between the amorphous state and the crystalline state due to the applied current, that is, Joule heat, and at this time, the resistivity of the phase change film having a crystalline state in which the resistivity of the phase change film having the amorphous state is crystalline. From the higher, the current flowing through the phase change film in the read mode is sensed to determine whether the information stored in the phase change memory cell is logic '1' or logic '0'.

On the other hand, in such a phase change memory device, a current flow of 1 kV or more is required for the phase change of the phase change film. Therefore, the contact area between the phase change film and the electrode must be made small to reduce the current required for the phase change of the phase change film.

1 is a cross-sectional view showing a conventional phase change memory device.

As shown, gates 3 are formed on the active region of the semiconductor substrate 1 defined by the isolation layer 2, and source / drain regions 4a are formed in the substrate surface on both sides of the gate 3. , 4b) is formed. A first insulating layer 5 is formed on the entire surface of the substrate to cover the gates 3, and a region to which a phase change cell is to be formed and a line to which a ground voltage is applied (hereinafter referred to as a "Vss line"). The first tungsten plug 6a and the second tungsten plug 6b are formed in the first insulating film portions of the region where the "

The second oxide film 7 is formed on the first oxide film 5 including the first and second tungsten plugs 6a and 6b, and the first conversion film forming region is formed in the phase conversion cell formation region according to a damascene process. A metal pad 8 having a dot shape is formed to contact the tungsten plug 6a, and a bar shape is formed to contact the second tungsten plug 6b in a region to which a ground voltage is to be applied. The ground line 9 is formed.

Subsequently, a third oxide film 10 is formed on the second oxide film 7 including the metal pad 8 and the ground line 9, and the third oxide film 10 in the region where the phase change cell is to be formed. A bottom electrode contact 11 in the form of a plug is formed in the portion to contact the metal pad 8. In addition, the phase conversion film 12 and the upper electrode 13 are sequentially stacked on the lower electrode contact 11 and the portion of the third oxide layer adjacent thereto, and as a result, the lower electrode of the plug shape, that is, And a phase change cell including a lower electrode contact 11, a phase change film 12 and an upper electrode 13 formed thereon in turn.

In addition, a fourth oxide film 14 is formed on the third oxide film 10 to cover the phase change cell, and the metal wiring 15 is disposed on the fourth oxide film 14 to contact the upper electrode 13. Formed.

However, according to the conventional phase change memory device as described above, a lower electrode having a size of 100 nm or less is formed on a metal pad, and a phase change film and an upper electrode are formed thereon. Therefore, since the contact size of the lower electrode is not uniformly formed in the whole wafer, the contact interface between the lower electrode and the phase conversion film is not constant, so that the write current distribution necessary for the phase change of the phase conversion film is widely formed.

In addition, since the size of the bottom electrode contact is small, it is difficult to fill the inside of the contact, and it is difficult to stably form the recess (recess) of the bottom electrode contact caused during the etch back process.

Accordingly, an object of the present invention is to provide a phase change memory device and a method for manufacturing the same, which can be made to solve the conventional problems as described above, and can make the current required for the phase change of the phase change film uniform.

Another object of the present invention is to provide a phase change memory device and a method of manufacturing the same, which can overcome process difficulties.

In order to achieve the above object, the present invention is a semiconductor substrate provided with a lower pattern and the first interlayer insulating film is formed to cover the lower pattern; A contact plug formed in the first interlayer insulating film; A lower electrode formed in the form of a pattern on the first interlayer insulating film including the contact plug; A second interlayer insulating film formed on the first interlayer insulating film to cover the lower electrode; A phase conversion film formed in the form of a plug in contact with the edge of the lower electrode in the second interlayer insulating film; And an upper electrode formed on the second interlayer insulating film including the phase change film.

In addition, the present invention includes a semiconductor substrate having a lower pattern and a first interlayer insulating film formed to cover the lower pattern; A contact plug formed in the first interlayer insulating film; A lower electrode formed in the form of a pattern on the first interlayer insulating film including the contact plug; A second interlayer insulating film formed on the first interlayer insulating film to cover the lower electrode; A phase conversion film formed in the second interlayer insulating film in a plug shape in contact with an edge of the lower electrode and formed in a pad shape on a portion of the second interlayer insulating film adjacent thereto; And an upper electrode formed on the phase conversion film.

In addition, the present invention includes a semiconductor substrate provided with a lower pattern and a first interlayer insulating film formed to cover the lower pattern; A contact plug formed in the first interlayer insulating film; A lower electrode formed in the form of a pattern on the first interlayer insulating film including the contact plug; A second interlayer insulating film formed on the first interlayer insulating film to cover the lower electrode; A contact hole formed to expose a side surface of a lower electrode in the second interlayer insulating film; A phase change film formed on the surface of the contact hole and a portion of the second interlayer insulating film adjacent to the contact hole; And an upper electrode formed in a shape to fill a contact hole on the phase conversion film.

The phase change memory devices of the present invention further include a nitride film formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film.

In addition, in order to achieve the above object, the present invention provides a semiconductor substrate comprising a lower substrate is formed and a first interlayer insulating film formed to cover the lower pattern; Forming a lower electrode on the first interlayer insulating layer in a pattern form; Forming a second interlayer insulating film on the first interlayer insulating film to cover the lower electrode; Etching the second interlayer insulating film to form a contact hole exposing an edge of a lower electrode; Forming a phase conversion film in a plug shape in the contact hole; And forming an upper electrode on the second interlayer insulating film including the phase conversion film.

In addition, the present invention includes providing a semiconductor substrate having a lower pattern and a first interlayer insulating film formed to cover the lower pattern; Forming a lower electrode on the first interlayer insulating layer in a pattern form; Forming a second interlayer insulating film on the first interlayer insulating film to cover the lower electrode; Etching the second interlayer insulating film to form a contact hole exposing an edge of a lower electrode; Forming a phase change material film on a second interlayer insulating film to fill the contact hole; Forming a conductive film on the phase change material film; And a pad shape disposed on the second interlayer insulating layer by etching the conductive film to form an upper electrode and etching the phase change material film to form a plug type phase change film contacting the edge of the lower electrode through the contact hole. It provides a method for manufacturing a phase conversion memory device comprising a.

In addition, the present invention provides a method of manufacturing a semiconductor device, comprising: providing a semiconductor substrate on which a lower pattern is formed and a first interlayer insulating film is formed to cover the lower pattern; Forming a lower electrode on the first interlayer insulating layer in a pattern form; Forming a second interlayer insulating film on the first interlayer insulating film to cover the lower electrode; Etching the second interlayer insulating film to form a contact hole exposing an edge of a lower electrode; Forming a phase change material film on the contact hole surface and the second interlayer insulating film with a uniform thickness; Forming a conductive layer on the phase change material layer to fill a contact hole; And etching the conductive layer to form an upper electrode, and etching the phase change material layer to form a phase change layer in contact with the edge of the lower electrode.

The method of the present invention may include forming a contact hole exposing the lower pattern by etching the first interlayer insulating layer before forming the lower electrode; And forming a contact plug in the contact hole, wherein the lower electrode is formed to contact the contact plug. A nitride film is formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, the technical principle of the present invention will be briefly described.

FIG. 2 is a diagram illustrating a reset current amount according to a contact size in a phase conversion memory device. As shown in FIG. 2, a stack for forming a lower electrode in a plug shape and a phase change layer on the lower electrode is shown. Compared to the structure, it can be seen that the amount of phase change current is smaller for the same contact size in the confined structure in which the lower electrode and the upper electrode are respectively formed in the pattern form and the phase conversion film is formed in the form of a plug between the electrodes.

Therefore, the present invention forms a flat lower electrode in the form of a pattern on the first contact plug, omitting the metal pad forming process using the margin process in the prior art, and then, the lower electrode After forming a contact hole exposing the edge of the phase, a phase change film is formed in the contact hole, and then a phase change cell is formed by forming an upper electrode on the phase change film.

In this case, the phase change film forms an interface at the edge of the lower electrode and also forms an interface with the upper electrode, thereby increasing Joule heat. In this case, the self-heater is generated in connection with the formation of the plug of the phase change film. The current can be made small, and a phenomenon in which the phase change occurs in the middle portion of the contact and the interface property is weak can be eliminated.

In addition, since it is not necessary to form a lower electrode contact having a size of 100 nm or less, it is possible to overcome the limitation problem of the exposure process, and also to solve the difficulty of filling the contact and the difficulty of stably forming the recess.

In detail, FIGS. 3A to 3F are plan views according to processes for describing a method of manufacturing a phase change memory device according to an embodiment of the present invention.

Referring to FIG. 3A, a semiconductor substrate 30 on which a lower pattern including a transistor is formed and a first interlayer insulating layer 31 formed of an oxide film is formed to cover the lower pattern. Then, after the nitride film 32 is formed on the first interlayer insulating film 31, the nitride film 32 and the first interlayer insulating film 31 are etched to form a portion of a lower pattern, for example, a source region of a transistor. A first contact hole 33 for exposing is formed.

Referring to FIG. 3B, a conductive film is deposited to bury the first contact hole 33 on the etched nitride film 32, and then chemical mechanical polishing (CMP) to expose the nitride film 32 to contact the lower pattern and the lower pattern. The contact plug 34 is formed.

Referring to FIG. 3C, a conductive film for the lower electrode is deposited on the nitride film 32 including the contact plug 34. Then, the conductive layer is patterned according to a known process to form a flat lower electrode 35 which contacts the contact plug 34 in the form of a pattern.

Here, in forming the lower electrode 35, since the lower electrode is conventionally formed in the form of a contact plug, it is not only difficult to reduce the contact hole size due to the limitation of the exposure process, but also contacts of uniform size throughout the wafer. Although there were difficulties in the process, such as the inability to form holes, the present invention can solve the above-described process problem, since the lower electrode is formed flat in the form of a pattern.

Referring to FIG. 3D, a second interlayer insulating film 36 made of an oxide film is formed on the nitride film 32 to cover the lower electrode 35, and then the surface thereof is CMP to planarize. Then, the second interlayer insulating film 36 having the surface planarized and the nitride film 32 thereunder are etched to form a second contact hole 37 exposing the edge of the lower electrode 35. In this case, the second contact hole 37 is preferably formed to have a size that is easy to fill in the deposition of the subsequent phase change material film.

Referring to FIG. 3E, a phase change material film is deposited to fill the second contact hole 37 on the second interlayer insulating film 36. Then, the CMP of the phase change material layer is exposed so that the second interlayer insulating layer 36 is exposed, and through this, the phase change forming a plug interface in the second contact hole 37 and forming a contact interface with an edge of the lower electrode 35. A film 38 is formed.

Referring to FIG. 3F, a conductive film for the upper electrode is deposited on the second interlayer insulating film 36 including the phase change film 38. Then, the conductive film is patterned according to a known process to form an upper electrode 39 in contact with the phase change film 38 on the second interlayer insulating film 36 including the phase change film 38. As a result, the lower electrode 35 formed in the pattern form, the plug-shaped phase change film 38 formed to contact the edge of the lower electrode 35, and the upper electrode formed on the phase change film 38 ( A phase change cell composed of 39) is formed.

Subsequently, although not shown, a series of known subsequent processes including a metallization process are sequentially performed to complete the manufacture of the phase change memory device according to the present invention.

In the phase change memory device of the present invention as described above, since the phase change film not only forms a contact interface with the edge of the lower electrode but also forms a contact interface with the upper electrode, the Joule heat through the interface with the lower electrode and the upper electrode Phase change of the phase change film occurs due to Joule heat through the interface and self-heat of the plug type phase change film itself. Therefore, the phase change memory device of the present invention can significantly lower the write current required for the phase change of the phase change film as compared with the conventional one.

In addition, in the phase change memory device of the present invention, since the phase change of the phase change film occurs in the middle portion A, rather than the contact interface with the electrode, the volume change caused by the phase change of the phase change film occurs. May occur in the middle portion of the phase change film, and thus, interface characteristics between the phase change film and the electrode, that is, fatigue characteristics may be improved.

Meanwhile, in the above-described embodiment of the present invention, the phase change film is simply formed in a plug shape, but may be formed in other shapes.

4 is a cross-sectional view illustrating a method of manufacturing a phase change memory device according to another exemplary embodiment of the present invention. As shown in FIG. 4, in this embodiment, the phase change film 38 is disposed in the second contact hole. The plug shape may be formed in a shape including a pad shape disposed on the second interlayer insulating layer 36.

In this case, the CMP process for the phase change material film is not necessary. After the phase change material film and the upper electrode conductive film are sequentially deposited on the second interlayer insulating film 36 including the second contact hole 37, the conductive film is deposited. When the film is etched, the phase change material film is etched together to form the upper electrode 39 and simultaneously form the phase change film 38 having a pad shape.

Therefore, in another embodiment of the present invention, compared to the previous embodiment, the CMP process for the phase change material film may be omitted, and thus the process may be simplified.

FIG. 5 is a cross-sectional view illustrating a method of manufacturing a phase change memory device according to still another embodiment of the present invention. As shown in FIG. 5, the second contact hole exposing the edge of the lower electrode 35 is exposed in this embodiment. 37) is formed to have a larger size than the previous embodiments.

In this case, the phase change film 38 is formed in a cylinder shape having a uniform thickness on the surface of the second contact hole 37 rather than filling the second contact hole 37. 39 is formed to fill the second contact hole 37.

In another embodiment of the present invention as described above, the CMP process for the phase change material film may be omitted, and the phase change film and the upper electrode may be formed at the same time as in the other embodiments, thereby simplifying the process. In addition, compared to the previous embodiments, it is possible to improve the difficulty of filling the second contact hole, and further, to increase the Joule heat by increasing the size of the contact interface between the phase change film and the upper electrode. Can be.

Hereinbefore, the present invention has been described with reference to some examples, but the present invention is not limited thereto, and those skilled in the art to which the present invention pertains have many modifications and variations without departing from the spirit of the present invention. It will be appreciated that it can be added.

As described above, the present invention can improve the Joule heat during the phase change of the phase conversion film by forming a phase conversion film in the form of a plug and making the interface between the edge of the lower electrode and the upper electrode, as well as the phase conversion film. Since self-heating of its own can be used, the write current required for the phase change of the phase conversion film can be significantly lowered compared with the conventional method.

In addition, the present invention can allow the phase change of the phase change film to occur in the intermediate portion of the phase change film rather than the contact interface with the electrode, thereby improving the interface characteristics between the phase change film and the electrode.

In addition, the present invention does not need to form a contact hole having a fine size in order to reduce the contact area between the phase change film and the electrode, thereby securing a process margin.

Claims (18)

A semiconductor substrate having a lower pattern and having a first interlayer dielectric layer formed to cover the lower pattern; A contact plug formed in the first interlayer insulating film; A lower electrode formed in the form of a pattern on the first interlayer insulating film including the contact plug; A second interlayer insulating film formed on the first interlayer insulating film to cover the lower electrode; A phase conversion film formed in the form of a plug in contact with the edge of the lower electrode in the second interlayer insulating film; And An upper electrode formed on the second interlayer insulating film including the phase conversion film; Phase change memory device comprising a. The method of claim 1, And a nitride film formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film. A semiconductor substrate having a lower pattern and having a first interlayer dielectric layer formed to cover the lower pattern; A contact plug formed in the first interlayer insulating film; A lower electrode formed in the form of a pattern on the first interlayer insulating film including the contact plug; A second interlayer insulating film formed on the first interlayer insulating film to cover the lower electrode; A phase conversion film formed in the second interlayer insulating film in a plug shape in contact with an edge of the lower electrode and formed in a pad shape on a portion of the second interlayer insulating film adjacent thereto; And An upper electrode formed on the phase conversion film; Phase change memory device comprising a. The method of claim 3, wherein And a nitride film formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film. A semiconductor substrate having a lower pattern and having a first interlayer dielectric layer formed to cover the lower pattern; A contact plug formed in the first interlayer insulating film; A lower electrode formed in the form of a pattern on the first interlayer insulating film including the contact plug; A second interlayer insulating film formed on the first interlayer insulating film to cover the lower electrode; A contact hole formed to expose a side surface of a lower electrode in the second interlayer insulating film; A phase change film formed on the surface of the contact hole and a portion of the second interlayer insulating film adjacent to the contact hole; And An upper electrode formed to fill a contact hole on the phase conversion film; Phase change memory device comprising a. The method of claim 5, And a nitride film formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film. Providing a semiconductor substrate having a lower pattern formed thereon and having a first interlayer dielectric film formed to cover the lower pattern; Forming a lower electrode on the first interlayer insulating layer in a pattern form; Forming a second interlayer insulating film on the first interlayer insulating film to cover the lower electrode; Etching the second interlayer insulating film to form a contact hole exposing an edge of a lower electrode; Forming a phase conversion film in a plug shape in the contact hole; And Forming an upper electrode on a second interlayer insulating film including the phase change film; A method for manufacturing a phase change memory device comprising a. The method of claim 7, wherein Before forming the lower electrode, Etching the first interlayer insulating film to form a contact hole exposing a lower pattern; And forming a contact plug in the contact hole. The method of claim 8, And the lower electrode is formed to contact the contact plug. The method of claim 7, wherein And a nitride film is formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film. Providing a semiconductor substrate having a lower pattern formed thereon and having a first interlayer dielectric film formed to cover the lower pattern; Forming a lower electrode on the first interlayer insulating layer in a pattern form; Forming a second interlayer insulating film on the first interlayer insulating film to cover the lower electrode; Etching the second interlayer insulating film to form a contact hole exposing an edge of a lower electrode; Forming a phase change material film on a second interlayer insulating film to fill the contact hole; Forming a conductive film on the phase change material film; And Forming an upper electrode by etching the conductive layer, and forming a plug type phase change layer contacting the edge of the lower electrode through the contact hole, including a pad shape disposed on the second interlayer insulating layer by etching the phase change material layer. step; A method for manufacturing a phase change memory device comprising a. The method of claim 11, Before forming the lower electrode, Etching the first interlayer insulating film to form a contact hole exposing a lower pattern; And forming a contact plug in the contact hole. The method of claim 12, And the lower electrode is formed to contact the contact plug. The method of claim 11, And a nitride film is formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film. Providing a semiconductor substrate having a lower pattern formed thereon and having a first interlayer dielectric film formed to cover the lower pattern; Forming a lower electrode on the first interlayer insulating layer in a pattern form; Forming a second interlayer insulating film on the first interlayer insulating film to cover the lower electrode; Etching the second interlayer insulating film to form a contact hole exposing an edge of a lower electrode; Forming a phase change material film on the contact hole surface and the second interlayer insulating film with a uniform thickness; Forming a conductive film to fill contact holes on the phase change material film; And Etching the conductive layer to form an upper electrode, and etching a phase change material layer to form a phase change layer in contact with an edge of the lower electrode; A method for manufacturing a phase change memory device comprising a. The method of claim 15, Before forming the lower electrode, Etching the first interlayer insulating film to form a contact hole exposing a lower pattern; And forming a contact plug in the contact hole. The method of claim 16, And the lower electrode is formed to contact the contact plug. The method of claim 15, And a nitride film is formed between the first interlayer insulating film, the lower electrode, and the second interlayer insulating film.

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