KR20050009873A - Method for forming isolation layer of semiconductor device - Google Patents

Abstract

PURPOSE: A method for forming an isolation layer of a semiconductor device is provided to decrease etch damage and stress damage occurring at the lower corner of a trench in etching and filling the trench by forming an ion implantation oxide layer under the trench such that the ion implantation oxide layer functions as an isolation layer. CONSTITUTION: A pad oxide layer and a pad nitride layer are sequentially deposited on a silicon substrate(21). The pad nitride layer and the pad oxide layer are etched to expose a part of the substrate corresponding to a field region. The exposed substrate is etched to form a trench. Oxygen ions are implanted into the lower part of the trench. A heat treatment is performed on the resultant structure to form an ion implantation oxide layer(26) right under the trench. A buried oxide layer is deposited on the front surface of the substrate to bury the trench. A CMP(chemical mechanical polishing) process is performed to expose the pad nitride layer. The pad nitride layer is eliminated.

Description

Method for forming isolation layer of semiconductor device

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 using a shallow trench isolation (STI) process.

With the progress of semiconductor technology, the speed and the high integration of semiconductor devices are progressing rapidly, and with this, the demand for refinement | miniaturization of a pattern and high precision of a pattern dimension is increasing. This requirement applies not only to patterns formed in device regions, but also to device isolation films that occupy a relatively large area. This is because the width of the device isolation region must be reduced in order to increase the width of the device region relatively in the trend that the width of the device region is decreasing.

Here, a conventional device isolation film has been formed by a LOCOS process, and the device isolation film by the LOCOS process, as is well known, has a bird's-beak having a beak shape at its edge portion. Since it is generated, there is a disadvantage of generating a leakage current while increasing the area of the device isolation layer.

Accordingly, a method of forming a device isolation layer using an STI process having a small width and excellent device isolation characteristics instead of the device isolation layer by the LOCOS process has been proposed. Currently, most semiconductor devices having a gate line width of 0.25 μm or less have an STI process. The device isolation film is formed.

1A to 1D are cross-sectional views illustrating a conventional method of forming a device isolation layer using an STI process, which will be described below.

Referring to FIG. 1A, a pad oxide film 12 and a pad nitride film 13 are sequentially formed on a semiconductor substrate 11, and a photoresist pattern (not shown) defining an isolation region on the pad nitride film 13 is formed. Form.

Next, the pad nitride layer 13 and the pad oxide layer 12 are etched using the photoresist pattern (not shown) as an etching barrier to expose the substrate portion corresponding to the field region.

Next, the trench 14 is formed using the exposed substrate region as a pad nitride film and a pad oxide film as an etch barrier.

Referring to FIG. 1B, an oxidation process is performed on the existing result to recover the etch damage applied to the semiconductor substrate 11 in the trench etching process. As a result, a sacrificial oxide film (not shown) of a thin film is formed on the surface of the trench 14. Subsequently, after the sacrificial oxide film (not shown) is removed, the thermal oxidation process 15 is again performed on the substrate product to form the thermal oxide film 15 on the trench surface.

Referring to FIG. 1C, a thick HDP-oxide layer 16 is deposited on the resultant so that the trench 14 is completely buried.

Referring to FIG. 1D, the HDP-oxide film is CMP until the pad nitride film 13 is exposed. Then, the pad nitride film used as the etch barrier during the trench etching is removed, and as a result, the trench type device isolation film 17 is formed.

In general, as the design rule of the isolation region (Isolation) gradually decreases, the depth of the trench is generally formed to 4000 Å in order to satisfy the device insulation characteristics of the trench.

However, the method of forming a device isolation layer using the conventional STI process as described above causes damage due to etching and stress at the corners of the trench bottom when the substrate is deeply etched to satisfy the device insulation characteristics due to the reduced design rule. .

Accordingly, an object of the present invention is to provide a method for forming a device isolation layer of a semiconductor device capable of mitigating damage caused during trench etching in an STI process.

1A to 1D are cross-sectional views of processes for describing a method of forming a device isolation film of a semiconductor device according to the related art.

2A to 2G are cross-sectional views illustrating processes of forming a device isolation film of a semiconductor device in accordance with an embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

21: semiconductor substrate 22: pad oxide film

23: pad nitride film 24: photosensitive film pattern

25: trench 26: ion implantation oxide film

27: buried oxide film 28: device isolation film

In order to achieve the above object, the present invention comprises the steps of depositing a pad oxide film and a pad nitride film on a silicon substrate in sequence; Etching the pad nitride film and the pad oxide film to expose a substrate portion corresponding to a field region; Etching the exposed substrate region to form a trench; Implanting oxygen into the lower portion of the trench; Heat treating the resultant substrate to form an ion implantation oxide layer directly under the trench; Depositing a buried oxide film over the entire surface of the substrate to fill the trench; CMP to expose the pad nitride film; And it provides a device isolation film forming method of a semiconductor device comprising the step of removing the pad nitride film.

Here, the trench is a device isolation film forming method of a semiconductor device, characterized in that to form a depth of 2000 ~ 3500Å. In addition, the ion implantation oxide film is a device isolation film forming method of a semiconductor device, characterized in that formed in a thickness of 1000 ~ 2000Å.

According to the present invention, since the present invention forms an ion implantation oxide film in the lower portion of the trench to serve as an isolation layer, instead of making the trench shallow to half of the desired depth, the etching depth is lowered. Accordingly, the corner of the lower portion of the trench It is possible to prevent damage due to etching and stress occurring in the.

(Example)

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

2A to 2G are cross-sectional views of processes for describing a method of forming a device isolation film according to an embodiment of the present invention.

Referring to FIG. 2A, a pad oxide film 22 and a pad nitride film 23 are sequentially deposited on the silicon substrate 21, and a photoresist pattern 24 defining a device isolation region is formed on the pad nitride film 23. do.

Subsequently, the pad nitride layer 23 and the pad oxide layer 22 are etched with CHF 4 gas or CF 4 gas using the photoresist pattern 24 as an etch barrier to expose the substrate portion corresponding to the field region.

Referring to FIG. 2B, the exposed substrate region is etched using the pad nitride layer 23 as an etch barrier to form a trench 25. In this case, the etching proceeds to dry etching using Cl 2 gas.

Here, if the depth of the trench 24 to be formed is 4000 kPa, it is about 2000-3000 kPa in this invention. This is because subsequent formation of the ion implantation oxide film can replace the predetermined depth of the device isolation film.

Referring to FIG. 2C, oxygen ions are implanted into the trench 25 where the etching is performed.

Referring to FIG. 2D, the photoresist pattern is removed.

Then, an ion implantation oxide film 26 is formed in the trench bottom portion through cleaning and thermal processes.

Here, the ion implantation has a low etching depth, thereby preventing damage that may occur in the lower corner of the trench.

Referring to FIG. 2E, the buried oxide layer 27 is deposited by chemical vapor deposition on the substrate resultant to completely fill the trench 25.

Here, since the trench is shallowly formed in the foregoing process, damage caused when the trench is buried can be reduced.

Referring to FIG. 2F, the buried oxide film 27 is CMP to expose the pad nitride film 23.

Referring to FIG. 2F, the pad nitride layer 23 used as an etch barrier at the time of trench etching is removed, thereby forming the device isolation layer 28 according to the present invention.

Up to now, the device isolation film formed through the above-described process replaces about half of the conventional device isolation film with an ion implantation oxide film, thereby effectively preventing the concentration of stress in the lower corners of the trench due to the etching depth increase during the trench formation process. have.

As described above, the present invention forms an ion implantation oxide film in the lower portion of the trench to act as a device isolation layer instead of shallowing the formation of the trench at half the normal depth, thereby reducing the etching depth, thereby reducing the trench depth during trench etching and filling. Damage caused by etching and stress occurring at the corners can be prevented.

Therefore, not only can the yield be improved and the reliability of the device isolation film itself can be secured, the reliability of the STI process can be secured, and the device characteristics can be improved.

In addition, this invention can be implemented in various changes in the range which does not deviate from the summary.

Claims (3)

Sequentially depositing a pad oxide film and a pad nitride film on a silicon substrate; Etching the pad nitride film and the pad oxide film to expose a substrate portion corresponding to a field region; Etching the exposed substrate region to form a trench; Implanting oxygen into the lower portion of the trench; Heat treating the resultant substrate to form an ion implantation oxide layer directly under the trench; Depositing a buried oxide film over the entire surface of the substrate to fill the trench; CMP to expose the pad nitride film; And And removing the pad nitride film. 2. The method of claim 1, wherein the trench is formed to a depth of 2000 to 3500 Å. The method of claim 1, wherein the ion implantation oxide film is formed to a thickness of 1000 ~ 2000Å.