KR20060122266A - Phase change ram device and method of manufacturing the same - Google Patents

Abstract

A phase change memory device and a method for manufacturing the same are provided to enhance the series resistance between a lower electrode contact and a phase change layer by forming a heater between the lower electrode contact and the phase change layer. An interlayer dielectric(2) is formed on a substrate(1) having a lower pattern. A contact plug(3) is formed in the interlayer dielectric. A lower electrode(4) is formed on the resultant structure to contact the contact plug. An oxide layer(5) is formed on the interlayer dielectric including the lower electrode. A recessed lower electrode contact is formed in the oxide layer to contact the lower electrode. A heater(8) is formed on the recessed lower electrode contact. A phase change layer(9) is formed on the heater. An upper electrode(10) is formed on the phase change layer.

Description

Phase change RAM device and method of manufacturing the same

1A to 1E are cross-sectional views illustrating processes for manufacturing a phase change memory device according to an exemplary embodiment of the present invention.

2A to 2E are cross-sectional views for each process for explaining a method of manufacturing a phase change memory device according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1 semiconductor substrate 2 interlayer insulating film

3: contact plug 4: lower electrode

5: oxide film 6: contact hole

7: bottom electrode contact 8: heater

9: phase change film 10: upper electrode

11: nitride film

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

Generally, a memory device is a volatile random access memory (RAM) device that loses input information when the power is cut off, and a ROM that keeps the input data stored even when the power is cut off. ) Are largely divided into elements. 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 is a very good memory device as is well known, high charge storage capability is required for periodic refresh operation, 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 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 new memory devices having characteristics of non-volatile memory devices and simple structures. For example, a phase change RAM device is proposed. It became.

The phase change memory device utilizes a difference in resistance between crystalline and amorphous particles due to a phase change of the phase conversion film interposed between the electrodes from a crystal state to an amorphous state through a current flow between the lower electrode and the upper electrode. To determine information stored in a cell.

In other words, the phase-conversion memory device uses a chalcogenide film as a phase-conversion film, which is a compound film composed of germanium (Ge), stevidium (Sb), and tellurium (Te). Phase change film), a phase change occurs between an amorphous state and a crystalline state by an applied current, that is, Joule heat, wherein the specific resistance of the phase change film having an amorphous state is crystalline. Since it is higher than the specific resistance of the phase change film having a state, 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 the phase change memory device described above, a current flow of 1 mA or more is required for stable phase change of the phase change film. Thus, a method of reducing the current required for the phase change of the phase change film by reducing the contact area between the phase change film and the lower electrode is implemented.

However, in the conventional phase change memory device, there is a limit in reducing the contact area between the phase change film and the lower electrode, and therefore, it is difficult to reduce the current required for the phase change of the phase change film.

Accordingly, an object of the present invention is to provide a phase change memory device capable of effectively lowering a phase change current and a method of manufacturing the same.

In order to achieve the above object, the present invention, a semiconductor substrate provided with a lower pattern; An interlayer insulating film formed on the semiconductor substrate to cover the lower pattern; A contact plug formed in the interlayer insulating film; A lower electrode formed on the contact plug and an interlayer insulating film portion adjacent thereto; An oxide film formed on the interlayer insulating film including the lower electrode; A lower electrode contact formed in the oxide layer to contact the lower electrode and having a recessed surface; A heater formed on the recessed lower electrode contact; A phase change film formed on the heater; And an upper electrode formed on the phase conversion film.

In addition, the present invention provides a semiconductor substrate having a lower pattern; Forming an interlayer insulating film on the substrate to cover the lower pattern; Forming a contact plug in the interlayer insulating film; Forming a lower electrode on the contact plug and an interlayer insulating film portion adjacent thereto; Forming an oxide film on the interlayer insulating film so as to cover the lower electrode; Etching the oxide layer to form a contact hole exposing a lower electrode; Forming a bottom electrode contact made of a TiN film and recessed in a surface of the contact hole; Heat treating the resultant substrate to form a heater formed of a TiON film on the recessed lower electrode contacts; And sequentially forming a phase conversion film and an upper electrode on a heater of the TiON film.

(Example)

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

1A to 1E are cross-sectional views illustrating processes for manufacturing a phase change memory device according to an exemplary embodiment of the present invention.

Referring to FIG. 1A, an interlayer insulating film 2 is formed on a semiconductor substrate 1 having a predetermined lower pattern (not shown) to cover the lower pattern. Thereafter, the interlayer insulating film 2 is etched to form a hole exposing the lower pattern or the substrate, and then a contact plug 3 is formed by embedding a conductive film, for example, a tungsten film in the hole. Subsequently, a metal film is deposited on the interlayer insulating film 2 including the contact plug 3, and then patterned to form a lower electrode 4 on the contact plug 3 and the portion of the interlayer insulating film adjacent thereto. Form.

Referring to FIG. 1B, an oxide film 5 is formed on the interlayer insulating film 2 to cover the lower electrode 4. Then, the oxide film 5 is etched to form a contact hole 6 exposing the lower electrode 4.

Referring to FIG. 1C, after depositing a metal film, preferably a TiN film, on the oxide film 5 to fill the contact hole 6, the TiN film is planarized by CMP (Chemical Mechanical Polishing). Then, an E-beam etch back is performed on the planarized TiN film to form a lower electrode contact 7 made of a TiN film having a surface recessed in the contact hole 6.

Referring to FIG. 1D, a heater 8 including a TiON film for Joule heating is formed on the oxide film 5 including the recessed lower electrode contact 7 by performing heat treatment on the substrate resultant.

Here, the heat treatment for forming the heater 8 of the TiON film is performed under the condition of flowing N 2 O gas at 40 to 50 sccm for 20 to 30 minutes at a pressure of 400 to 500 mTorr and a temperature of 200 to 300 ° C. In addition, the heater 8 of the TiON film is formed to a thickness of 100 kPa or less, for example, 50 to 100 kPa.

Referring to FIG. 1E, a phase change material layer and an upper electrode material layer are sequentially deposited on the heater 8 of the TiON film. Then, the upper electrode material layer, the phase change material layer, and the heater 8 of the TiON film are etched to form a stacked structure of the phase change film 9 and the upper electrode 10 on the heater 8.

Thereafter, a series of well-known subsequent steps are carried out in order to complete the manufacture of the phase change memory device according to the present invention.

In the above-described phase change memory device of the present invention, the heater made of the TiON film increases the series resistance between the lower electrode contact and the phase change film, so that the difference between the reset and the set resistance is increased so that the sensing window is increased. Therefore, the current required for the phase change of the phase change film can be effectively reduced.

Meanwhile, in the present invention described above, in order to lower the current required for the phase change of the phase change film, it is preferable to reduce the contact area between the lower electrode contact and the phase change film on the premise of interposing a heater between the lower electrode contact and the phase change film. Should be.

However, when the contact hole in which the lower electrode contact is formed is reduced in order to reduce the contact area between the lower electrode contact and the phase conversion film, the contact filling is not made stable, and thus it is difficult to secure desired device characteristics.

Therefore, before the heater is formed, the present invention increases the upper size of the contact hole in the process of forming the lower electrode contact, thereby making the contact filling stable.

2A to 2C are cross-sectional views illustrating processes for manufacturing a phase change memory device according to another exemplary embodiment of the present invention. Here, only the parts different from the previous embodiment will be described schematically. Also, the same parts as in the previous embodiment are denoted by the same reference numerals.

Referring to FIG. 2A, after the oxide film 5 is formed on the interlayer insulating film 2 on which the lower electrode 4 is formed, the nitride film 11 is formed on the oxide film 5. Here, the nitride film 11 is to increase the size of the contact hole in the subsequent to ensure that the contact is buried.

Referring to FIG. 2B, the nitride film 11 and the oxide film 5 are etched to form a contact hole 6 exposing the lower electrode 4.

Referring to FIG. 2C, an isotropic etching process is performed on the etched nitride film 11 to increase the upper size of the contact hole 6.

Referring to FIG. 2D, a TiN film is deposited on the nitride film 11 including the contact hole 6 having a relatively large top size. Then, the TiN film is subjected to the CMP process and planarized, and subsequently, the E-beam etch back process is performed to form the lower electrode contact 7 made of the TiN film having the recessed surface.

Here, when the TiN film is deposited, the contact buried is stable because the upper size of the contact hole 6 is relatively large, and thus, stable device characteristics can be secured in the manufactured phase change memory device.

Referring to FIG. 2E, a heat treatment is performed on the substrate resultant to form the heater 8 of the TiON film, and then the phase conversion film 9 and the upper electrode 10 are sequentially formed on the heater 8.

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 effectively lower the current required for the phase change of the phase conversion film by increasing the series resistance between the lower electrode contact and the phase conversion film by interposing a heater between the lower electrode contact and the phase conversion film. The speed of the phase change memory element can be improved.

In addition, the present invention can improve device characteristics by relatively increasing the size of the upper portion of the contact hole in which the lower electrode contact is to be formed, thereby improving the contact filling property of the lower electrode contact material.

Claims (10)

A semiconductor substrate having a lower pattern; An interlayer insulating film formed on the semiconductor substrate to cover the lower pattern; A contact plug formed in the interlayer insulating film; A lower electrode formed on the contact plug and an interlayer insulating film portion adjacent thereto; An oxide film formed on the interlayer insulating film including the lower electrode; A lower electrode contact formed in the oxide layer to contact the lower electrode and having a recessed surface; A heater formed on the recessed lower electrode contact; A phase change film formed on the heater; And And an upper electrode formed on the phase change film. The phase change memory device according to claim 1, further comprising a nitride film formed on said oxide film. The phase change memory device as claimed in claim 1, wherein the lower electrode contact is made of a TiN film, and the heater is made of a TiON film. The phase change memory device as claimed in claim 1, wherein the heater is formed to a thickness of 50 to 100 microseconds. 4. The phase change memory device as claimed in claim 3, wherein the heater of the TiON film is formed by heat treatment of a lower electrode contact of the TiN film. Providing a semiconductor substrate having a lower pattern; Forming an interlayer insulating film on the substrate to cover the lower pattern; Forming a contact plug in the interlayer insulating film; Forming a lower electrode on the contact plug and an interlayer insulating film portion adjacent thereto; Forming an oxide film on the interlayer insulating film so as to cover the lower electrode; Etching the oxide layer to form a contact hole exposing a lower electrode; Forming a bottom electrode contact made of a TiN film and recessed in a surface of the contact hole; Heat treating the resultant substrate to form a heater formed of a TiON film on the recessed lower electrode contacts; And And sequentially forming a phase conversion film and an upper electrode on the heater of the TiON film. 7. The method of claim 6, further comprising forming a nitride film on the oxide film after forming the oxide film and before forming the contact hole. The method of claim 7, further comprising, after forming the contact hole, increasing the contact hole upper size by isotropically etching the nitride layer. The method of claim 6, wherein the forming of the heater of the TiON film is characterized in that the flow of N 2 O gas at 40 to 50 sccm for 20 to 30 minutes at a pressure of 400 ~ 500mTorr and a temperature of 200 ~ 300 ℃ Method of manufacturing a phase change memory device. The phase change memory device according to claim 6, wherein the heater of the TiON film is formed to have a thickness of 50 to 100 kPa.

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