KR100237013B1 - Method of forming an element field oxide film in a semiconductor device - Google Patents

Abstract

The present invention relates to a method of forming a field oxide film of a semiconductor device, each of which forms trenches in silicon substrates on both sides of a device isolation region in order to prevent generation of bird's beak generated during a local oxide of silicon (LOCOS) process. Afterwards, a nitride film is embedded in the trench to prevent side penetration of the oxidant during the oxidation process. Therefore, the present invention relates to a method of forming a field oxide film of a semiconductor device in which the generation of buzz big due to lateral penetration of the oxidant is prevented, thereby reducing the size of the active region, and thus improving the integration of the device in an easy manner.

Description

Field oxide film formation method of a semiconductor device

The present invention relates to a method of forming a field oxide film of a semiconductor device, and more particularly to a method of forming a field oxide film of a semiconductor device to prevent the size of the active region from being reduced.

In general, in the manufacturing process of a semiconductor device, a field oxide film is formed in a device isolation region in order to electrically separate a device and a device, or a peripheral region and a memory cell region. The field oxide film may be formed by various methods such as a LOCOS process or a trench method. Then, a method of forming a field oxide film of a conventional semiconductor device using a LOCOS process will be described with reference to FIGS. 1A and 1B. As follows.

Conventionally, as shown in FIG. 1A, the pad oxide film 2 and the nitride film 3 are sequentially formed on the silicon substrate 1, and the nitride film 3 is exposed to expose the silicon substrate 1 in an isolation region. And the pad oxide film 2 is sequentially patterned. Then, the silicon substrate 1 of the exposed portion is oxidized by the oxidation process using the patterned nitride film 3 as an oxidation prevention layer to form the field oxide film 4 as shown in FIG. 1B. However, the LOCOS process made as described above has the following problems.

First, since the BZBIC (part A) is formed at both sides of the field oxide film 4 due to the side penetration of the oxidant during the oxidation process, the size of the active region is reduced, which makes it difficult to integrate the device. Second, a white ribbon phenomenon occurs in the edge portion of the bird's beak (A portion) to make the thickness of the gate oxide film thinner than other portions, thereby deteriorating the electrical characteristics of the device.

Therefore, in the present invention, a method of forming a field oxide film of a semiconductor device capable of resolving the above-described disadvantages by forming trenches in silicon substrates at both sides of the device isolation region and then embedding a nitride film in the trench to prevent side penetration of the oxidant during the oxidation process. The purpose is to provide.

The present invention for achieving the above object is to form a trench in each of the silicon substrate on both sides of the device isolation region, and after forming a first oxide film on the entire upper surface so that the trench is embedded from the first oxide film Forming a first nitride film on the substrate; sequentially patterning the first nitride film and the first oxide film to expose the silicon substrate of the device isolation region from the step; and then forming a second nitride film over the entire upper surface of the trench to fill the trench. Forming a portion of the second nitride film and etching the partial thickness of the second nitride film and the first nitride film to expose the silicon substrate between the trenches, and oxidizing the exposed silicon substrate between the trenches. Removing the remaining first and second nitride films after forming the field oxide film; and And embedding a second oxide film in the trench, wherein the first oxide film is removed by dry etching and the second nitride film is removed by wet etching.

1A and 1B are cross-sectional views of a device for explaining a method of forming a field oxide film of a conventional semiconductor device.

2A to 2H are cross-sectional views of a device for explaining a method of forming a field oxide film of a semiconductor device according to the present invention.

* Explanation of symbols for main parts of the drawings

1 and 11: silicon substrate 2: pad oxide film

3: nitride film 4 and 16: field oxide film

12: trench 13: first oxide film

14: first nitride film 15: second nitride film

17: second oxide film

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

2A to 2H are cross-sectional views of devices for describing a method of forming a field oxide film of a semiconductor device according to the present invention, and FIG. 2A is a state in which trenches 12 are formed on silicon substrates 11 at both sides of a region to be separated from each other. As a cross-sectional view, the depth X of the trench 12 is determined in consideration of the thickness of the field oxide film to be formed.

2B is a cross-sectional view of a state in which the first nitride film 14 is formed on the first oxide film 13 after the first oxide film 13 is formed on the entire upper surface such that the trench 12 is buried.

FIG. 2C is a cross-sectional view of the first nitride layer 14 and the first oxide layer 13 sequentially patterned to expose the silicon substrate 11 in the device isolation region. In this case, dry etching is performed to dry the trench ( The first oxide film 13 embedded in 12 is completely removed.

FIG. 2D is a cross-sectional view of the second nitride film 15 formed on the entire upper surface of the trench 12 so as to fill the trench 12, and FIG. 2E illustrates the silicon substrate 11 exposed between the trenches 12. 2 is a cross-sectional view of a part of the entire thickness of the nitride film 15 and the first nitride film 14, wherein oxidation of the silicon substrate 11 occurs when the second and first nitride films 15 and 14 remain. Since this is not done, a slight overetch is performed so that the silicon substrate 11 between the trenches 12 is completely exposed.

FIG. 2F is a cross-sectional view of the field oxide film 16 formed by oxidizing the exposed silicon substrate 11 between the trenches 12, and an oxidant due to the second nitride film 15 embedded in the trench 12. The side penetration of is completely blocked so no buzzvik is produced.

FIG. 2G is a cross-sectional view of a state in which the remaining first nitride film 14 and second nitride film 15 are completely removed, and the second nitride film 15 embedded in the trench 12 by wet etching is completely removed. To be removed.

FIG. 2H illustrates that a portion of the field oxide film 16 and the first oxide film 13 existing on the silicon substrate 11 after the second oxide film 17 is embedded in the trench 12 is removed. It is sectional drawing of the state in which the formation of the oxide film 16 was completed.

As described above, according to the present invention, trenches are formed in silicon substrates on both sides of the device isolation region in order to prevent the generation of buzz big generated during the LOCOS process, and the nitride film is embedded in the trench to prevent side penetration of the oxidant during the oxidation process. do. Therefore, according to the present invention, first, the generation of the buzz big due to the side penetration of the oxidant is prevented to prevent the reduction of the size of the active region, and thus it is possible to improve the integration of the device in an easy way. Second, the occurrence of the white ribbon phenomenon is prevented, so that the electrical characteristics of the device are not degraded. Third, the channel stop ion is not injected by deepening the trench, thereby simplifying the process steps. Can be done. And fourth, the depth of the trench can be arbitrarily adjusted to increase the device isolation effect.

Claims (3)

In the field oxide film forming method of a semiconductor device, Forming trenches in the silicon substrates at both sides of the device isolation region, Forming a first oxide film on the entire upper surface of the trench to fill the trench, and then forming a first nitride film on the first oxide film; Sequentially patterning the first nitride film and the first oxide film to expose the silicon substrate of the device isolation region from the step, and then forming a second nitride film on the entire upper surface of the trench to fill the trench; Etching a portion of thicknesses of the second nitride film and the first nitride film to expose the silicon substrate between the trenches from the step; Oxidizing the exposed silicon substrate between the trenches to form a field oxide film and removing the remaining first and second nitride films after the step; And embedding a second oxide film in the trench from the step. The method of claim 1, The method of claim 1, wherein the first oxide layer is removed by dry etching. The method of claim 1, The second nitride film is a method of forming a field oxide film of a semiconductor device, characterized in that the removal by wet etching.

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