JPH07201842A - Manufacturing for semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to form a gettering region in a scribing line on a face of a wafer while a field oxide film is formed. CONSTITUTION:A field oxide film 5 is formed in a PBLOCOS method. In a gettering region 9, a silicon substrate 1 is selectively oxidized after a polysilicon film 3 for relaxation of stress is removed. Then, the stress to the silicon substrate 1 is enlarged so that a large amount of crystal defects 7 as a gettering source is induced in the silicon substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a gettering technique for eliminating impurities and crystal defects that deteriorate element characteristics from an element region.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, if an alkali metal such as Na or K, a heavy metal such as Fe or Cu, or a crystal defect is present inside the device, deterioration of the device characteristics is caused, so that impurities and crystals of these elements are generated. A process called gettering is performed to remove defects by segregating them outside the element region by high temperature processing.

As the gettering treatment, there are intrinsic gettering utilizing oxygen existing in the substrate and extrinsic gettering in which a strained layer is formed on the back surface of a semiconductor substrate and impurities are trapped therein.

[0004]

However, the intrinsic gettering has a problem that a step for forming oxygen precipitation defects inside the substrate is required and that the wafer is likely to be warped.

Further, in the method of forming the strained layer on the back surface of the semiconductor substrate, since the back surface side of the semiconductor substrate is used as the gettering region, there is a problem that the gettering effect on the front surface side of the substrate is small.

Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor device which can form a gettering region on the front surface side of a semiconductor substrate without increasing the number of steps so much.

[0007]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor device according to the present invention provides an element region including an element isolation region and an element formation region surrounded by the element isolation region, and A step of forming a polycrystalline silicon film on a semiconductor substrate having a portion near the element region; a step of forming a silicon nitride film on the polycrystalline silicon film; and a step of forming the silicon nitride film on the element region. The first opening is locally formed by etching to form the first opening on the element isolation region, and the silicon nitride film on a portion near the element area is locally etched to form a second opening at a predetermined position. And further locally etching the polycrystalline silicon film through the second opening to form a third opening continuous with the second opening of the silicon nitride film into the polycrystalline silicon film. Forming the film and oxidizing the polycrystalline silicon film and the semiconductor substrate through the first opening of the silicon nitride film in the device region, and at the same time, in the vicinity of the device region, the silicon nitride film The method includes the step of oxidizing the surface of the semiconductor substrate through the second opening and the third opening of the polycrystalline silicon film, and the step of removing the silicon nitride film and the polycrystalline silicon film, respectively.

In one aspect of the present invention, after forming a silicon oxide film on the semiconductor substrate, the polycrystalline silicon film is formed.

According to one aspect of the present invention, a polycrystalline silicon film is formed on a semiconductor substrate having an element region including an element isolation region and an element formation region surrounded by the element isolation region and a portion near the element region. And the step of removing the polycrystalline silicon film on a portion in the vicinity of the element region, the step of forming a silicon nitride film on the entire surface, the silicon nitride film is locally etched, and the element isolation is performed. Forming a first opening on the region and forming a second opening at a predetermined position on the vicinity of the device region; and through the first opening of the silicon nitride film in the device region. The polycrystalline silicon film and the semiconductor substrate are respectively oxidized, and at the same time, the semiconductor substrate is passed through the second opening of the silicon nitride film in the vicinity of the element region. And a step of oxidizing the surface, and removing the silicon nitride film and the polycrystalline silicon film, respectively.

[0010]

In the present invention, a so-called poly-silicon buffered LOCOS (PBL) in which a polycrystalline silicon film for stress relaxation is interposed between the semiconductor substrate and the silicon nitride film.
When the OCOS) method is carried out, the polycrystalline silicon film in the vicinity of the element region is locally or entirely removed and the semiconductor substrate in that part is selectively oxidized, so that the semiconductor substrate is applied in the vicinity of the element region. The stress is increased, a large amount of crystal defects are induced in that portion, and a gettering region is formed. As a result, a device isolation region and a gettering region can be simultaneously formed on the surface of the semiconductor substrate, and a special process for forming the gettering region is unnecessary, which is almost the same as the conventional PBLOCOS method. Can be realized in numbers.

Further, since the gettering region is formed in the vicinity of the element region on the front surface side of the semiconductor substrate, the gettering effect against the contamination from the front surface side of the substrate is great.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings with reference to the embodiments.

FIG. 1 is a schematic cross-sectional view showing a method of forming an element isolation region and a gettering region according to the first embodiment of the present invention in the order of steps. In each figure, a portion of an element region 8 including an element isolation region and an element formation region surrounded by the element isolation region is shown on the left side, and a portion 9 near the element region, for example, a scribe line portion is shown on the right side.

First, as shown in FIG. 1A, a silicon oxide film 2 having a thickness of 200 to 400 Å is formed on a silicon substrate 1 by thermal oxidation in an oxidizing atmosphere of water vapor or oxygen.

Next, by a chemical vapor deposition method, 500 to 1
A polycrystalline silicon film 3 having a thickness of 000Å is formed on the entire surface.

Next, by chemical vapor deposition method, 1500 Å
A silicon nitride film 4 having a thickness of 1 is formed on the entire surface.

Next, as shown in FIG. 1B, an opening 10 is formed in the silicon nitride film 4 in the element region 8 by a photoetching technique, and an opening 11 is formed in the silicon nitride film 4 in the portion 9 near the element region. To form. Further, after covering the entire element region 8 with photoresist, etching is performed in the portion 9 near the element region using the silicon nitride film 4 as a mask to form an opening continuous with the opening 11 in the polycrystalline silicon film 3.

Next, as shown in FIG. 1C, thermal oxidation is performed using the silicon nitride film 4 as an oxidation resistant film, and in the element region 8, the polycrystalline silicon film 3 and the silicon substrate 1 are selectively oxidized. In addition to forming the silicon oxide film 5, the surface portion of the silicon substrate 1 is selectively oxidized in the element region vicinity portion 9 to form the silicon oxide film 6. The thermal oxidation is performed under the condition that a desired field oxide film thickness can be obtained. In this embodiment,
Pyrooxidation is performed at a temperature of 900 to 1000 ° C. for 90 minutes.

At this time, in the element region 8, PBLOCOS
Although a silicon oxide film 5 which is a field oxide film is formed by the method, the silicon substrate 1 in the opening portion of the polycrystalline silicon film 3 is thermally oxidized in the portion 9 in the vicinity of the element region. Therefore, when the silicon oxide film 6 is expanded in volume. The stress applied to the silicon substrate 1 increases, and a relatively large amount of crystal defects 7 are induced in the silicon substrate 1. Since these crystal defects 7 can trap impurities such as heavy metals, they can be used as a gettering source.

Next, as shown in FIG. 1D, the silicon nitride film 4, the polycrystalline silicon film 3 and the silicon oxide film 2 are removed. If necessary, the silicon oxide film 6 on the crystal defects 7 may be entirely removed.

Through the above steps, the field oxide film 5 and the gettering region in the vicinity of the element region can be simultaneously formed as in the PBLOCOS method.

FIG. 2 is a schematic sectional view showing a method of forming an element isolation region and a gettering region according to a second embodiment of the present invention in the order of steps. In each figure, a portion of an element region 8 including an element isolation region and an element formation region surrounded by the element isolation region is shown on the left side, and a portion 9 near the element region, for example, a scribe line portion is shown on the right side.

First, as shown in FIG. 2A, a silicon oxide film 2 having a thickness of 200 to 400 Å is formed on the silicon substrate 1 by thermal oxidation in an oxidizing atmosphere of water vapor, oxygen or the like.

Next, by a chemical vapor deposition method, 500 to 1
A polycrystalline silicon film 3 having a thickness of 000Å is formed on the entire surface.

Next, the portion of the element region 8 is masked with a resist, and the polycrystalline silicon film 3 in the portion 9 in the vicinity of the element region is removed by etching.

Next, as shown in FIG. 2B, a silicon nitride film 4 having a thickness of 1500 Å is formed on the entire surface by chemical vapor deposition.

Next, as shown in FIG. 2C, openings 10 and 11 are formed in the silicon nitride film 4 in the element region 8 and the element region vicinity portion 9 by a photoetching technique.

Next, as shown in FIG. 2D, thermal oxidation is performed using the silicon nitride film 4 as an oxidation resistant film, and in the element region 8, the polycrystalline silicon film 3 and the silicon substrate 1 below the opening 10 are removed. The silicon oxide film 5 is selectively oxidized to form the silicon oxide film 5, and the silicon oxide film 6 is formed by selectively oxidizing the surface portion of the silicon substrate 1 below the opening 11 in the element region vicinity portion 9. The thermal oxidation is performed under the condition that a desired field oxide film thickness can be obtained. In the present embodiment, the temperature is 900-
90 minutes at 1000 ° C.

At this time, in the element region 8, PBLOCOS
A silicon oxide film 5 which is a field oxide film is formed by the method, but since the polycrystalline silicon film 3 for stress relaxation does not exist in the portion 9 near the element region, the silicon substrate 1 is expanded when the silicon oxide film 6 is expanded in volume. The stress applied to the substrate becomes large, and a relatively large amount of crystal defects 7 are induced in the silicon substrate 1. Since these crystal defects 7 can trap impurities such as heavy metals, they can be used as a gettering source.

Next, as shown in FIG. 2E, the silicon nitride film 4, the polycrystalline silicon film 3 and the silicon oxide film 2 are removed. If necessary, the silicon oxide film 6 on the crystal defects 7 may be entirely removed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and the above-mentioned embodiments are based on the technical idea of the present invention and various effective modifications and It can be applied. For example, the gettering region is a region that is effective as a gettering source in the vicinity of the device region of the device, and it suffices to select a region that does not adversely affect the electrical characteristics of the device, and other than the scribe line, for example, in the peripheral portion of the chip. It can also be formed. Further, the silicon oxide film 2 is originally provided to relieve stress on the silicon substrate 1 in the PBLOCOS method. Therefore, in the portion 9 near the element region, the silicon oxide film 2 should be removed or previously formed. Alternatively, the polycrystalline silicon film 3 or the silicon nitride film 4 may be directly formed on the silicon substrate 1.

[0032]

According to the present invention, the gettering region can be formed near the device region on the front surface side of the semiconductor substrate at the same time as forming the device isolation insulating film by the PBLOCSO method. Therefore, an effective gettering region can be formed without increasing the number of manufacturing steps of the conventional semiconductor device.

Further, since the gettering region is formed on the surface side of the semiconductor substrate, the gettering region can be formed in the vicinity of the element region, and the gettering effect against the contamination from the surface can be enhanced. .

As a result, the performance and reliability of the semiconductor device can be improved, and the manufacturing yield and throughput can be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a method of forming an element isolation region and a gettering region according to a first embodiment of the present invention in the order of steps.

FIG. 2 is a schematic cross-sectional view showing a method of forming an element isolation region and a gettering region according to a second embodiment of the present invention in the order of steps.

[Explanation of symbols]

 1 Silicon Substrate 2 Silicon Oxide Film 3 Polycrystalline Silicon Film 4 Silicon Nitride Film 5 Silicon Oxide Film (Field Oxide Film) 6 Silicon Oxide Film (Gettering Region) 7 Crystal Defects 8 Element Region 9 Element Area Neighboring Area 10, 11 Opening

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/301 H01L 21/78 L

Claims (3)

[Claims] 1. A step of forming a polycrystalline silicon film on a semiconductor substrate having an element region including an element isolation region and an element formation region surrounded by the element isolation region, and a portion in the vicinity of the element region, Forming a silicon nitride film on the polycrystalline silicon film, locally etching the silicon nitride film on the device region to form a first opening on the device isolation region, and The silicon nitride film above the portion near the element region is locally etched to form a second
Is formed, and the polycrystalline silicon film is locally etched through the second opening to form a third opening continuous with the second opening of the silicon nitride film in the polycrystalline silicon film. And oxidizing the polycrystalline silicon film and the semiconductor substrate through the first opening of the silicon nitride film in the element region, and at the same time, in the vicinity of the element region, the first portion of the silicon nitride film And a step of oxidizing the surface of the semiconductor substrate through the second opening and the third opening of the polycrystalline silicon film, and a step of removing the silicon nitride film and the polycrystalline silicon film, respectively. Manufacturing method of semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the polycrystalline silicon film is formed after forming a silicon oxide film on the semiconductor substrate. 3. A step of forming a polycrystalline silicon film on a semiconductor substrate having an element region including an element isolation region and an element formation region surrounded by the element isolation region, and a portion near the element region, A step of removing the polycrystalline silicon film on a portion near the element region, a step of forming a silicon nitride film on the entire surface, and a step of locally etching the silicon nitride film to form a first layer on the element isolation region. Forming the first opening and forming a second opening at a predetermined position on the vicinity of the element region, and the polycrystalline silicon film through the first opening of the silicon nitride film in the element region. And simultaneously oxidizing the semiconductor substrate, and simultaneously oxidizing the surface of the semiconductor substrate through the second opening of the silicon nitride film in the vicinity of the element region. Degree and method of manufacturing a semiconductor device characterized by a step of removing each said silicon nitride film and the polycrystalline silicon film.