KR20070063808A - Phase change memory device and manufacturing method thereof - Google Patents

Abstract

A phase change memory device and its manufacturing method are provided to reduce effectively the current necessary for a phase change by reducing a contact area between a phase changeable layer and an upper electrode using a porous hemi-spherical Al2O3 layer. A lower pattern is formed on a semiconductor substrate(21). A first electrode is formed on the resultant structure to contact the lower pattern. A phase changeable layer(24a) is formed on the first electrode. A porous hemi-spherical Al2O3 layer(25a) is formed on the phase changeable layer. The porous hemi-spherical Al2O3 layer is capable of exposing partially the phase changeable layer to the outside. A second electrode is formed on the resultant structure.

Description

Phase change RAM device and method of manufacturing the same

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

2A to 2E are cross-sectional views illustrating processes for manufacturing a phase change memory device according to an embodiment of the present invention.

3 is a sectional view showing a phase change memory device according to another embodiment of the present invention;

Explanation of symbols on the main parts of the drawings

21 semiconductor substrate 22 interlayer insulating film

23: lower electrode 24: phase change material film

24a: phase change film 25: Al film

25a: Al2O3 film 26: contact film

27 conductive film 27a 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 that can be driven with low current and a method of manufacturing the same.

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

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 requires a higher operating voltage than 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 have been conducted to develop a new memory device having the characteristics of the nonvolatile memory device and having a simple structure. As an example, a phase change memory device (Phase) has recently been developed. Change RAM) has been 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 crystalline state to the amorphous state through the current flow between the lower electrode and the upper electrode. Determine the information stored in

In other words, the phase conversion memory element 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 write and read modes is sensed to determine whether the information stored in the phase change memory cell is logic '1' or logic '0'.

1 is a cross-sectional view illustrating a conventional phase change memory device, which will be described below.

As shown, gates 4 are formed on the semiconductor substrate 1, and a junction region (not shown) is formed in the substrate surface on both sides of the gate 4. An interlayer insulating film 5 is formed on the entire surface of the substrate 1 to cover the gates 4, and in the interlayer insulating film portions of the region where the phase change cell is to be formed and the region where the ground voltage Vss is to be applied. The first tungsten plug 6a and the second tungsten plug 6b are formed, respectively.

The first oxide film 7 is formed on the interlayer insulating film 5 including the first and second tungsten plugs 6a and 6b, and although not shown in detail, the first tungsten film is formed in the region where the phase change cell is to be formed. A dot-type metal pad 8 is formed in contact with the plug 6a, and a bar-type ground line Vss line is in contact with the second tungsten plug 6b in an area to which a ground voltage is to be applied. 9) is formed.

The second oxide film 10 is formed on the first oxide film 7 including the metal pad 8 and the ground line 9, and the metal pad (10) is formed in the second oxide film 10 in the region where the phase change cell is to be formed. A lower electrode 11 in the form of a plug is formed in contact with 8). The phase conversion film 12 and the upper electrode 13 are stacked on the second oxide film 10 in contact with the lower electrode 11 in a pattern form, and thus, the plug-type lower electrode 11 and the upper electrode 13 are stacked thereon. The phase change cell comprised of the laminated phase change film 12 and the upper electrode 13 is comprised. The third oxide film 14 is formed on the second oxide film 10 to cover the phase change cell, and the metal wiring 15 contacting the upper electrode 13 is formed on the third oxide film 14. Formed.

On the other hand, in such a phase-change memory element, high current flow, for example, 1 mA or more is required for stable phase change of the phase-conversion film. Therefore, conventionally, the contact area between the phase-conversion film and the electrode is made as small as possible in both contact surfaces. The current density was to cause Joule heat to increase rapidly. At this time, in order to reduce the current through the transistor and increase the Joule heat efficiency, it is necessary to make the contact area between the phase change film and the lower electrode as small as possible, and thus, increase the current density during the phase change of the phase change film.

However, due to limitations of current exposure techniques and etching techniques, there is a limit in reducing the contact area between the phase change film and the electrodes.

In addition, according to the conventional phase change memory device shown in FIG. 1, although the phase change film 12 is in contact with the upper electrode 13 as well as the lower electrode 11, both contact surfaces are used as the phase change region. Therefore, the portion of the phase change film in contact with the lower electrode 11 is usually used as the phase change region.

Therefore, the phase change of the phase change film 12 depends on the contact resistance with the lower electrode 11. As described above, the contact area between the lower electrode 11 and the phase change film 13 is presently described. Is difficult to form stably, and therefore, the rate of change of contact resistance becomes large, resulting in low reliability.

Accordingly, an object of the present invention is to provide a phase change memory device and a method of manufacturing the same, which can be driven with low current without being affected by the limitations of exposure and etching techniques.

In order to achieve the above object, the present invention, a semiconductor substrate having a lower pattern; A first electrode formed to contact the lower pattern; A phase change film formed on the first electrode; A porous hemispherical Al 2 O 3 film formed to expose a portion thereof on the phase change film; And a second electrode formed on the phase change film including the porous hemispherical Al 2 O 3 film.

Here, the first electrode is formed in a plug shape in an interlayer insulating film formed on the substrate to cover the lower pattern, and the phase change film is formed in a pattern shape disposed on the first electrode and the interlayer insulating film adjacent thereto.

The second electrode may be formed of a single conductive film having a surface planarization, or may be a laminated film of a TiN contact film formed on a phase change film including a porous hemispherical Al2O3 film and planarized, and a conductive film formed on the contact film. Is done.

In addition, in order to achieve the above object, the present invention, forming a first electrode on a semiconductor substrate having a lower pattern; Forming a phase conversion film on the first electrode; Forming a porous hemispherical Al 2 O 3 film exposing a portion thereof on the phase change film; And forming a second electrode on the phase change film including the porous hemispherical Al 2 O 3 film.

The forming of the first electrode may include forming an interlayer insulating film on a semiconductor substrate having a lower pattern; Etching the interlayer insulating layer to form a contact hole exposing a lower pattern; And embedding a conductive film in the contact hole.

The forming of the porous hemispherical Al 2 O 3 film may include forming an Al film on the phase change film; And electrolytic anodic oxidation of the Al film, wherein the Al film is formed to a thickness of 100 to 200 Å.

The electrolyte anodizing of the Al film may include applying a positive voltage to the Al film while immersing an Al film-formed substrate in an electrolyte solution, and placing a negative electrode spaced apart from the substrate in the electrolyte solution to generate a positive oxidation reaction. Do so.

As the electrolyte solution, an acidic solution of any one of oxalic acid, phosphoric acid and sulfuric acid is used, and the negative electrode is made of platinum or carbon.

The second electrode may be formed of a single conductive film having surface planarization, or may be formed of a laminated film of a TiN contact film that is planarized and a conductive film formed on the contact film on a phase change film including a porous hemispherical Al2O3 film. .

(Example)

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

2A through 2E are cross-sectional views illustrating processes of manufacturing a phase change memory device according to an exemplary embodiment of the present invention.

Referring to FIG. 2A, after the semiconductor substrate 21 including a lower pattern (not shown) including a transistor is provided, an interlayer insulating layer 22 is formed on the entire surface of the substrate 21 to cover the lower pattern. Then, a contact hole for exposing a lower pattern is formed in the interlayer insulating film 22 according to a known process, and then a conductive film is embedded in the contact hole to form a plug-type first electrode, that is, the lower electrode 23. Form.

Referring to FIG. 2B, the phase change material layer 24 and the Al layer 25 are sequentially formed on the interlayer insulating layer 22 including the plug-type lower electrode 23. Here, the phase change material film 24 may include at least one of Sb-Te, Ag, In, or Sn doped with at least one of Ge-Sb-Te, Ge-Bi-Te, Al, In, Sn, or Bi. This doped Bi-Te is applied. The Al film 25 is 200 kPa or less, preferably 100 to 200 kPa thick.

Referring to FIG. 2C, a porous substrate for exposing predetermined portions of the phase change material layer 24 on the phase change material layer 24 by electrolytically anodizing the Al layer with the Al resultant substrate resulted in the electrolyte solution. A hemispherical Al2O3 film 25a is formed.

Here, the electrolyte anodic oxidation of the Al film is performed by applying a positive voltage to the Al film while immersing the substrate product in which the Al film is formed in the electrolyte solution, and negatively formed of platinum or carbon by being spaced apart from the substrate product in the electrolyte solution. The electrode is placed in such a manner that a positive oxidation reaction occurs, wherein an acidic solution such as oxalic acid, phosphoric acid or sulfuric acid is used as the electrolyte solution.

Referring to FIG. 2D, a contact film 26 made of TiN is formed on the phase change material film 24 including the porous hemispherical Al2O3 film 25a. In this case, the contact layer 26 is formed to achieve planarization by easily embedding the porous hemispherical Al2O3 film. Next, a conductive film 27 for a second electrode, that is, an upper electrode, is formed on the contact film 26.

Referring to FIG. 2E, the conductive layer 27 and the contact layer 26 are etched to form the upper electrode 27a formed of the laminated layers of the layers 27 and 26, and then the porous hemispherical Al 2 O 3 layer 25a is formed. And then, the phase change material film is etched to form a phase change film 24a. As a result, a phase change cell composed of the lower electrode 23, the phase change film 24a, and the upper electrode 27a. Configure

Thereafter, 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 according to the present invention manufactured as described above, since the contact area between the phase change film and the upper electrode is reduced by the porous hemispherical Al2O3 film on the phase change film, the phase change of the phase change film is substantially This is achieved at the interface with the upper electrode, and in this case, the contact area is so small that it is possible to significantly lower the current required for the phase change.

Accordingly, the present invention can very easily implement a phase change memory device capable of driving with a low current without being affected by the limitations of exposure and etching techniques.

Meanwhile, in the embodiment of the present invention described above, a contact film is formed on a porous hemispherical Al2O3 film to achieve planarization, and then a conductive film is formed to form an upper electrode as a laminated film of the contact film and the conductive film. As an example, as shown in FIG. 3, a conductive film having surface planarization is formed on the porous hemispherical Al2O3 film 25 without forming a contact film, thereby forming an upper electrode 27a formed of a single film of the conductive film. have.

In addition, although not shown, in the above-described embodiments, the lower electrode is formed in the form of a plug, and the phase conversion film is formed in the form of a pattern. As another embodiment, the lower electrode is formed in the form of a pattern, and the upper The conversion film can be formed in the form of a plug.

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, since the present invention reduces the contact area between the phase change film and the upper electrode by using a porous hemispherical Al2O3 film, it is possible to effectively lower the current required for the phase change of the phase change film.

In addition, since the present invention reduces the contact area between the phase change film and the upper electrode by forming an Al 2 O 3 film, it is possible to easily and reliably implement a phase change memory device that can be driven at a low current without being affected by the limitations of exposure and etching techniques. have.

Claims (15)

A semiconductor substrate having a lower pattern; A first electrode formed to contact the lower pattern; A phase change film formed on the first electrode; A porous hemispherical Al 2 O 3 film formed to expose a portion thereof on the phase change film; And A second electrode formed on the phase change film including the porous hemispherical Al2O3 film; Phase change memory device comprising a. The method of claim 1, The first electrode is formed in a plug shape in an interlayer insulating film formed on a substrate so as to cover a lower pattern, and the phase change film is formed in a pattern form disposed on the first electrode and an interlayer insulating film adjacent thereto. device. The method of claim 1, And the second electrode is made of a single conductive film having surface planarization. The method of claim 1, And the second electrode comprises a contact film formed on a phase change film including a porous hemispherical Al2O3 film for flattening and a laminated film of a conductive film formed on the contact film. The method of claim 4, wherein And the contact film is made of a TiN film. Forming a first electrode on a semiconductor substrate having a lower pattern; Forming a phase conversion film on the first electrode; Forming a porous hemispherical Al 2 O 3 film exposing a portion thereof on the phase change film; And Forming a second electrode on the phase change film including the porous hemispherical Al 2 O 3 film; A method for manufacturing a phase change memory device comprising a. The method of claim 6, The forming of the first electrode may include forming an interlayer insulating film on a semiconductor substrate having a lower pattern; Etching the interlayer insulating layer to form a contact hole exposing a lower pattern; And embedding a conductive layer in the contact hole. The method of claim 6, The forming of the porous hemispherical Al 2 O 3 film may include forming an Al film on the phase change film; And electrolytic anodizing the Al film. The method of claim 8, And the Al film is formed to a thickness of 100 to 200 microseconds. The method of claim 6, Electrolytic anodic oxidation of the Al film may include applying a positive voltage to the Al film and placing a negative electrode spaced apart from the substrate in the electrolyte solution while soaking the substrate product on which the Al film is formed in an electrolyte solution. A method for manufacturing a phase change memory device, characterized in that to perform an oxidation reaction. The method of claim 10, And the electrolyte solution is any one acid solution selected from the group consisting of oxalic acid, phosphoric acid and sulfuric acid. The method of claim 10, And the cathode is made of platinum or carbon. The method of claim 6, And the second electrode is formed of a single conductive film having surface planarization. The method of claim 6, And the second electrode is formed of a laminated film of a contact film to be planarized on a phase change film including a porous hemispherical Al2O3 film and a conductive film formed on the contact film. The method of claim 14, And the contact film is formed of a TiN film.

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