KR100548520B1 - method for forming an isolation in a semiconductor device - Google Patents

Abstract

A device isolation film formation method of a semiconductor device is disclosed. After etching the substrate partially exposed by the pad oxide film pattern and the pad nitride film pattern to form a trench in the substrate, an oxide film and a polysilicon film are formed on the surface of the pad nitride film pattern and the sidewalls and bottom of the trench. The polysilicon layer and the oxide layer are polished in sequence until the surface of the pad nitride layer pattern is exposed, and then the exposed pad nitride layer pattern and the pad oxide layer pattern are sequentially removed. As a result, a structure is obtained in which the oxide film and the polysilicon film are filled in the trench. Then, the resultant having the structure is heat-treated to oxidize the polysilicon film of the structure. Here, in the case of the polysilicon film subjected to the oxidation, volume expansion proceeds outward in the trench. Therefore, the force applied to the trench can be balanced.

Description

Method for forming an isolation in a semiconductor device

1 and 2 are cross-sectional views illustrating an element isolation film of a semiconductor device formed by a conventional method.

3A to 3F are cross-sectional views illustrating a method of forming an isolation layer in a semiconductor device according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a device isolation film of a semiconductor device, and more particularly, to a method of forming a device isolation film of a semiconductor device having a shallow trench isolation (STI) structure.

Conventional device isolation structures can be formed by performing thermal field oxidation processes such as silicon partial oxidation (LOCOS). According to the silicon partial oxidation method, bird's beak frequently occurs at the end of the field oxide film while oxygen penetrates to the side of the oxide film from the lower part of the nitride film used as the anti-oxidation mask during selective oxidation. As described above, when a buzz beak occurs, the width of the active area is reduced because the length of the field oxide film is extended to the active area by the buzz beak.

Therefore, in recent years in the manufacture of semiconductor devices, a shallow trench element isolation structure is in the spotlight as an element isolation film. An example of an isolation layer having the shallow trench isolation structure is disclosed in US Pat. No. 6,140,208 (issued to Agahi, et al.).

Referring to FIG. 1, the trench isolation structure, that is, the trench isolation layer has a structure in which an oxide film 14 is filled in the trench 12 formed in the substrate 10. However, pressure is applied to the trench 12 as in the direction of the arrow in FIG. 1, and the pressure applied in this way concentrates on the lower portion of the trench 12. Specifically, since the Argen particles B injected into the substrate when the source / drain electrodes are formed are subsequently activated and inserted into the lattice of the substrate 10 to further expand the substrate 10 in the direction of the arrow. The expansion is under pressure in the lower portion A of the trench 12. In addition, shrinkage occurs when the oxide film 14 filled in the trench 12 is heat-treated. In this way, the generated shrinkage progresses in the direction of the arrow, and as a result, pressure is applied to the lower portion A of the trench 12.

Accordingly, as shown in FIG. 2, dislocation C is generated under the trench 12, resulting in deterioration of the trench isolation layer. As described above, deterioration of the trench isolation layer acts as a cause of an increase in leakage current, thereby lowering electrical reliability of the semiconductor device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of forming a trench isolation layer of a semiconductor device for relieving pressure applied to a trench.

According to another aspect of the present invention, there is provided a method of forming a trench isolation layer, including forming a pad oxide layer pattern and a pad nitride layer pattern on a substrate to expose a portion of the substrate; Etching the exposed substrate to form a trench; Forming an oxide film on a surface of the pad nitride film pattern and on sidewalls and a bottom of the trench; Forming a polysilicon film to a thickness of 100 to 2,000 kPa to fill the trench on the oxide film; Polishing the polysilicon film and the oxide film in sequence until the surface of the pad nitride film pattern is exposed such that the polysilicon film remains only in the trench; Removing the exposed pad nitride layer pattern and the pad oxide layer pattern in order to form a structure in which the oxide layer and the polysilicon layer are filled in the trench; And oxidizing the polysilicon film remaining in the trench by a thermal oxidation method.

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Here, when the thickness of the polysilicon film is less than 100 GPa, it is not preferable because the trench may not be sufficiently filled. In addition, when the thickness of the polysilicon film exceeds 2,000 kPa, it is not preferable because it becomes thicker than the single film structure filled in the conventional trench. That is, it is not preferable when the thickness of the conventional single film formed for filling the trench and the thickness of the oxide film and the polysilicon film formed for filling the trench of the present invention are significantly different. Therefore, the polysilicon film is preferably formed to have a thickness of 100 to 2,000 kPa.

When the heat treatment is performed at a temperature of less than 700 ° C., the oxidation of the polysilicon film does not proceed easily. However, when the heat treatment is performed at a temperature condition exceeding 1,100 ° C., the polysilicon may be used. It is not preferable because it does not easily control the oxidation of the film. Therefore, the heat treatment is preferably carried out at a temperature of 700 to 1,100 ℃. As described above, when the heat treatment is performed at the temperature of 700 to 1,100 ° C, the polysilicon film is oxidized in the range of about 50 to 500 kPa.

As described above, according to the present invention, an oxidized polysilicon film is applied as one of the thin films to be filled in the trench in the structure of the trench isolation film. Here, in the case of the polysilicon film subjected to the oxidation, volume expansion proceeds outward in the trench. Therefore, when the source / drain electrodes are formed, the Argen particles injected into the substrate are subsequently activated while being inserted into the lattice of the substrate to inflate the substrate and the direction of the volume expansion becomes opposite to each other. . As such, the forces applied to the trenches cancel each other out so that the balance of the forces can be maintained. Therefore, since little pressure is applied to the lower portion of the trench, defects such as dislocation are hardly generated.

(Example)

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

3A to 3F are cross-sectional views illustrating a method of forming an isolation layer in a semiconductor device according to an embodiment of the present invention.

Referring to FIG. 3A, the pad oxide layer 32 and the pad nitride layer 34 are sequentially formed on the substrate 30. Subsequently, after forming a photoresist film on the pad nitride film 34, a photolithography process is performed to form the photoresist film as a photoresist pattern 35 exposing the photoresist film as a part of the pad nitride film 34.

Referring to FIG. 3B, the exposed pad nitride layer 34 is removed by etching using the photoresist pattern 35 as an etching mask. In addition, the exposed pad oxide layer 32 is removed by removing the pad nitride layer 34. Then, the photoresist pattern 35 is removed using an oxygen plasma. Accordingly, the pad nitride film pattern 34a and the pad oxide film pattern 32a are formed on the substrate 30 to expose a portion of the substrate 30. Subsequently, etching is performed using the pad nitride film pattern 34a as an etching mask to remove the substrate 30 having a portion exposed. As a result, a trench 37 is formed in the substrate 30.

Referring to FIG. 3C, an oxide film 38 is continuously formed on the surface of the pad nitride film pattern 34a and the sidewalls and the bottom of the trench 37. At this time, the oxide film 38 mainly selects the plasma enhanced oxide film (PE-OX) because the peeling characteristics should be considered. Subsequently, a polysilicon film 40 is formed on the resultant in which the oxide film 38 is formed. At this time, the polysilicon film 40 is formed to be sufficiently filled in the trench 37 and is formed to have a thickness of about 500 GPa from the surface of the oxide film 38.

3D and 3E, the polysilicon film 40 and the oxide film 38 are polished sequentially. And, the polishing is mainly accomplished by chemical mechanical polishing. In this case, the polishing is performed until the surface of the pad nitride film pattern 34a is exposed. Accordingly, the polysilicon film 40a and the oxide film 38a remain in the trench 37 by removing the polysilicon film 40 and the oxide film 38 formed on the pad nitride film pattern 34a by the polishing.

Subsequently, the pad nitride film pattern 34a and the pad oxide film pattern 32a formed on the substrate 30 are sequentially removed. Accordingly, a structure in which the oxide film 38a and the polysilicon film 40a are filled in the trench 37 is formed in the substrate 30. In other words, an isolation layer having a trench isolation structure is formed on the substrate 30.

Referring to FIG. 3F, the resultant structure in which the oxide film 38a and the polysilicon film 40a are filled in the trench 37, that is, the device isolation layer is heat-treated. At this time, the heat treatment is carried out at a temperature of about 800 ℃. As described above, the polysilicon film 40a of the device isolation film is oxidized by performing the heat treatment. That is, the polysilicon film 42 which has been oxidized is obtained by performing the above heat treatment. At this time, the oxidation is in the range of about 200 kPa. Accordingly, a structure in which the oxide film 38a is oxidized with the polysilicon film 42 which is oxidized is formed in the trench 37 as a device isolation film having trench device isolation.

In the polysilicon film 42 obtained by performing the oxidation, the volume expansion proceeds in the outward direction of the trench 37 as in the direction of the arrow. Therefore, since the oxide film 38a formed in the trench 37 contracts, the pressure is applied to the trench 37 to be opposite to each other, thereby canceling the force. In addition, when the source / drain electrodes are formed, the Argen particles injected into the substrate 30 are subsequently activated and inserted into the lattice of the substrate 30 to inflate the substrate 30 and the direction of the volume expansion. Because it is the opposite, the offset of force is achieved.

As described above, according to the present invention, by applying the polysilicon film oxidized as the structure of the trench isolation layer, it is possible to maintain the balance of the force applied to the trench. Therefore, since little pressure is applied to the lower portion of the trench, defects such as dislocation are hardly generated. Therefore, there is an effect that the electrical reliability of the semiconductor device can be sufficiently secured.

While the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated that it can be changed.

Claims (3)

Forming a pad oxide layer pattern and a pad nitride layer pattern on the substrate to expose a portion of the substrate; Etching the exposed substrate to form a trench; Forming an oxide film on a surface of the pad nitride film pattern and on sidewalls and a bottom of the trench; Forming a polysilicon film to a thickness of 100 to 2,000 kPa to fill the trench on the oxide film; Polishing the polysilicon film and the oxide film in sequence until the surface of the pad nitride film pattern is exposed such that the polysilicon film remains only in the trench; Removing the exposed pad nitride layer pattern and the pad oxide layer pattern in order to form a structure in which the oxide layer and the polysilicon layer are filled in the trench; And And oxidizing the polysilicon film remaining in the trench by a thermal oxidation method. delete The method of claim 1, wherein the thermal oxidation is performed at a temperature of 700 to 1,100 ° C. 3.

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