JPH07201976A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] A gettering region is formed on the scribe line on the front surface of the wafer at the same time when the field oxide film is formed. [Configuration] When the field oxide film 4 is formed by the LOCOS method, the gettering region 8 has a thickness of 2000 to 500.
By selectively oxidizing the silicon substrate 1 using the silicon nitride film 3 having a large film thickness of 0 Å or more, the silicon substrate 1
The stress applied to is increased to induce a large amount of crystal defects 6 as a gettering source 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 first silicon nitride film that covers the element region and has an opening in the element isolation region, and a film thickness larger than the first silicon nitride film on the semiconductor substrate having a portion near the element region. Through a step of forming a second silicon nitride film covering a portion in the vicinity of the element region and having an opening at a predetermined position, through the opening of the first silicon nitride film and the opening of the second silicon nitride film. The method includes a step of oxidizing the surface portion of the semiconductor substrate, and a step of removing the first and second silicon nitride films.

In one aspect of the present invention, the second silicon nitride film is formed to a thickness of 2000 Å or more.

In one aspect of the present invention, after forming a silicon oxide film on the semiconductor substrate, the first and second silicon nitride films are formed.

According to one aspect of the present invention, a silicon nitride 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. Step and etching the silicon nitride film on the element region to a predetermined thickness, and locally etching the silicon nitride film on a predetermined position in the vicinity of the element region to form a recess. A step of forming, a step of etching the silicon nitride film to form an opening in each of the element isolation region and a portion in the vicinity of the element region at the predetermined position, and a surface portion of the semiconductor substrate through the opening Respectively, and a step of removing the silicon nitride film.

[0011]

According to the present invention, the surface of the semiconductor substrate is selectively oxidized while a relatively large stress is applied to the semiconductor substrate by using a silicon nitride film having a large film thickness, and thereby gettering is performed on the surface side of the semiconductor substrate. Form an area. The selective oxidation of the substrate surface can be performed simultaneously with the formation of the element isolation region by the LOCOS method. Therefore, the element isolation region and the gettering region can be formed at the same time without increasing the number of steps.

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 on the contamination from the front surface side of the substrate is great.

[0013]

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 sectional view showing a method of forming an element isolation region and a gettering region according to an embodiment of the present invention in the order of steps. In each figure, a portion of an element region 7 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 8 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, 2000-
A silicon nitride film 3 having a thickness of 3000Å is formed on the entire surface.

Next, as shown in FIG. 1B, the silicon nitride film 3 in the element region 7 is shaved off by about 500 to 1500 Å by a photoetching technique. At this time, in the portion 8 near the element region, the silicon nitride film 3 at the position of the opening 9 for later forming the silicon oxide film 5 is also etched at the same time and scraped off by about 500 to 1500 Å, and the recess 9 ′ is provided at the position corresponding to the opening 9. To form.

Next, as shown in FIG. 1C, the silicon nitride film 3'in the element region 7 is formed by the photoetching technique.
At the same time as forming the opening 10 in the silicon nitride film 3, the opening 9 is formed in the silicon nitride film 3 in the portion 8 near the element region. At this time, by forming a recess 9 ′ in a position corresponding to the opening 9 of the silicon nitride film 3 in advance, the opening 10 of the silicon nitride film 3 ′ is formed.
The opening 9 and the opening 9 of the silicon nitride film 3 can be formed almost at the same time.

Next, as shown in FIG. 1 (d), the silicon substrate 1 is thermally oxidized by using the silicon nitride films 3 and 3'as oxidation resistant films, respectively, so that the silicon oxide film 5 is formed under the openings 9 and 10. And 4 respectively. Thermal oxidation
It is performed under the condition that a desired field oxide film thickness can be obtained. In this embodiment, the temperature is 900 to 1000 ° C. and is 90 by pyrooxidation.
Minutes.

At this time, in the element region 7, a normal LOCO is formed.
Although the silicon oxide film 4 which is a field oxide film is formed by the S method, the film thickness of the silicon nitride film 3 is larger than that of the silicon nitride film 3'in the portion 8 in the vicinity of the element region, so that the silicon oxide film 5 is formed. The stress applied to the silicon substrate 1 increases due to the volume expansion at the time, and a relatively large amount of crystal defects 6 are induced in the silicon substrate 1. Since these crystal defects 6 can trap impurities such as heavy metals, they can be used as a gettering source. For this purpose, the thickness of the silicon nitride film 3 is preferably 2000 Å or more, more preferably 5000 Å or more.

Next, as shown in FIG. 1E, the silicon nitride films 3, 3'and the silicon oxide film 2 are removed. If necessary, the silicon oxide film 5 on the crystal defects 6 may be entirely removed.

Through the above steps, the field oxide film 4 and the gettering region in the vicinity of the element region can be formed at the same time as in the normal LOCOS method.

The gettering region is a region effective as a gettering source near the device region of the device, and a region which does not adversely affect the electrical characteristics of the device may be selected. It can also be formed in the peripheral portion.

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 silicon oxide film 2 is originally provided to relieve the stress from the silicon nitride film to the silicon substrate 1 in the LOCOS method. Therefore, the silicon oxide film 2 is removed in the element region vicinity portion 8. Alternatively, the silicon nitride film 3 may be directly formed on the silicon substrate 1 without being formed in advance.

[0025]

According to the present invention, the gettering region can be formed in the vicinity of the device region on the front surface side of the semiconductor substrate while forming the device isolation insulating film by the LOCSO 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 an embodiment of the present invention in the order of steps.

[Explanation of Codes] 1 silicon substrate 2 silicon oxide film 3, 3'silicon nitride film 4 silicon oxide film (field oxide film) 5 silicon oxide film (gettering region) 6 crystal defect 7 device region 8 device region vicinity 9, 10 openings

Claims (4)

[Claims] 1. A semiconductor substrate having an element region consisting of an element isolation region and an element formation region surrounded by the element isolation region and a portion near the element region, the element region being covered and the element isolation region being covered. A first silicon nitride film having an opening at a portion and a second silicon nitride film having a larger film thickness than the first silicon nitride film and covering a portion near the element region and having an opening at a predetermined position. A step of forming, a step of oxidizing the surface portion of the semiconductor substrate through the opening of the first silicon nitride film and the opening of the second silicon nitride film, respectively, and the first and second silicon nitride films. And a step of removing the semiconductor device. 2. The second silicon nitride film having a thickness of 2000 Å
The method for manufacturing a semiconductor device according to claim 1, wherein the film thickness is formed as described above. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the first and second silicon nitride films are formed after forming a silicon oxide film on the semiconductor substrate. . 4. A step of forming a silicon nitride 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; Etching the silicon nitride film on the region to a predetermined thickness, and locally forming a recess by locally etching the silicon nitride film on a predetermined position in the vicinity of the element region, A step of etching the silicon nitride film to form an opening in each of the element isolation region and a portion in the vicinity of the element region at the predetermined position; and a step of oxidizing each surface portion of the semiconductor substrate through the opening. And a step of removing the silicon nitride film, the method of manufacturing a semiconductor device.