JPH1050694A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device which enables micromachining, suppression of the bird's beak and reduction in the stress on a substrate. SOLUTION: On an Si substrate 101, a pad oxide film 102 and silicon nitride film 103 are formed, and holes are selectively formed into field oxide film- forming regions. A silicon nitride film 106 is deposited in the opened grooves and dry etched to form side walls 107. Nitrogen ions are implanted to form side walls of the N-contained silicon oxide film and Si substrate region 109. The grooves bottom faces are dry etched to form shallow grooves 110. A thick oxide film 110 is formed as a field oxide film, and finally the silicon nitride film 103 and side walls 107' are etched. As other embodiments, the oxide film 106 may be a polysilicon oxide or an amorphous Si film.

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 an element isolation forming step.

[0002]

2. Description of the Related Art In a method of manufacturing a semiconductor device, in particular, as to a device isolation forming step, an oxidation preventing film (silicon nitride film) selectively formed on a pad oxide film as a known method.
Is used as a mask to obtain a field oxide film (thick silicon oxide film) as an element isolation film.

Then, for flattening, Japanese Patent Laid-Open No.
There is a technique of performing field oxidation after etching a silicon substrate in a region where field oxidation is to be formed as in 19137 to form a concave portion.

In order to suppress a bird's beak, the pad oxide film is removed as in Japanese Patent Application Laid-Open No. Hei 4-230034, and then the exposed portion of the pad oxide film and the region where the field oxide film is to be formed are nitrided, and the substrate is etched. There was technology.

[0005]

However, there is a problem in the conventional element isolation formation process that it is difficult to miniaturize, to suppress bird's beaks, and to reduce stress on the substrate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device which can be miniaturized, suppresses bird's beaks, and can reduce stress on a substrate. is there.

[0007]

According to the present invention, in a step of forming a field oxide film, an antioxidant film is selectively provided on a silicon substrate via a pad oxide film, and a region where the antioxidant film is opened is provided. Removing the pad oxide film, further etching the silicon substrate to form a groove, oxidizing the silicon substrate in the opening to form a silicon oxide film, providing a side wall in the groove, A step of obliquely ion-implanting N (nitrogen), a step of removing a silicon oxide film on the bottom of the groove, and a step of oxidizing using the side wall of the groove and the antioxidant film as a mask. .

In the step of providing a side wall on the oxidation preventing film, the side wall is formed of a silicon oxide film.

Further, in the step of providing a side wall on the oxidation preventing film, the side wall is formed of a polysilicon film or an amorphous silicon film.

[0010]

According to the method of manufacturing a semiconductor device of the present invention, by providing a side wall on a mask layer at the time of field oxidation, it is possible to miniaturize the side wall as compared with a space opened by using photolithography technology. Also, N
By implanting (nitrogen), it becomes possible to prevent O (oxygen), which is an oxidizing agent, from entering during formation of the field oxide film.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail based on examples. 1 and 2 are cross-sectional views of a wafer along a process sequence of a method of manufacturing a semiconductor device of the present invention, and FIGS. 3 and 4 are cross-sectional views of a wafer along a process sequence of a conventional method of manufacturing a semiconductor device. .

In FIG. 1, reference numerals 101, 201, 301 and 401 are silicon substrates. 102, 202, 302, 402
Is a silicon oxide film. 103, 203, 303, 4
03 is a silicon nitride film. 104, 204, 30
Reference numerals 4 and 404 denote resists. 105, 205, 305
Denotes a groove in a region where field oxidation is to be formed. 106 is C
VD silicon oxide film. Reference numeral 206 denotes a CVD polysilicon film or an amorphous silicon film. 107 is a side wall of the silicon oxide film. Reference numeral 207 denotes a side wall of the CVD polysilicon film or the amorphous silicon film. 10
7 'is a side wall of the silicon oxide film into which nitrogen is mixed.
Reference numeral 207 ′ is a sidewall of a CVD polysilicon film or an amorphous silicon film into which nitrogen is mixed. 108, 20
8 is N (nitrogen ion). 109, 208, 405
Is a silicon substrate mixed with nitrogen. Reference numeral 406 denotes a silicon oxide film in which nitrogen is mixed. 110, 210,
Reference numeral 407 denotes a groove formed by etching a portion mixed with nitrogen. 111, 211, 306, and 408 are field oxide films.

First, the prior art will be briefly described. FIG.
As shown in (a), a pad oxide film 302 for stress relaxation is formed on a silicon substrate 301 wafer.

Next, the silicon nitride film 30 is formed by CVD.
After depositing No. 3, a resist 304 is applied, and a region where an element isolation region is to be formed is opened using photolithography technology.

Then, as shown in FIG. 3B, the silicon nitride film 303 and the pad oxide film 302 in the opened regions are dry-etched.

Further, as shown in FIG. 3 (c), the silicon substrate in the opened region is dry-etched to form a shallow groove 305.

Then, as shown in FIG. 3D, a thick oxide film 306 is formed as a field oxide film by performing thermal oxidation using the silicon nitride film 303 as a mask.

Then, after etching the silicon oxide film thinly formed on the silicon nitride film 303, the silicon nitride film 303 is etched with hot phosphoric acid to obtain the structure shown in FIG. This technique aims at flattening which is required to form a more accurate pattern when using a photolithography technique in a later step.

FIG. 4 will be described as another technique. As shown in FIG.
On the wafer 01, a silicon oxide film 402 is formed as a pad film for stress relaxation.

Next, the silicon nitride film 40 is formed by CVD.
After depositing No. 3, a resist 404 is applied, and a region where an element isolation region is to be formed is opened using photolithography.

Then, as shown in FIG. 4B, the silicon nitride film 403 and the pad oxide film 402 in the opened region are selectively dry-etched.

Further, as shown in FIG. 4 (c), the silicon substrate and the exposed silicon oxide film in the open area are nitrided.

Next, as shown in FIG. 4D, a shallow groove 406 is formed in the opened region by dry etching.

Then, as shown in FIG. 4E, a thick oxide film 407 is formed as a field oxide film by performing thermal oxidation using the silicon nitride film 403 as a mask to obtain the structure of FIG. 4F. . This technology is also aimed at suppressing bird's beaks.

Now, embodiments of the present invention will be described. First, FIG. 1 will be described. As shown in FIG. 1A, a silicon substrate 101 is formed to form an element isolation region.
8 pad oxide film to relieve stress
A silicon oxide film 102 having a thickness of several tens of degrees to 300 degrees is grown by thermal oxidation in an oxygen atmosphere at 00 ° C. to 1100 ° C. or in a steam atmosphere.

Next, 800 wafers are formed on the entire surface of the wafer by CVD.
A silicon nitride film 103 having a thickness of {2000} is deposited. Then, after a resist film 104 is applied on the entire surface of the wafer, a region where a field oxide film is to be formed is selectively opened by photolithography.

Next, as shown in FIG. 1B, CH ₄ or CH ₄ is applied by a dry etching method under a pressure of several hundred mTorr.
The silicon nitride film in the resist opening is etched using an O ₂ etching gas.

Further, as shown in FIG. 1 (c), the silicon oxide film is etched by dry etching using a CHF ₃ etching gas under a pressure of several Torr.
By dry etching, C under a pressure of several hundred mTorr
Plasma is generated with an F ₄ etching gas at a flow rate of several tens of cc / min and RF power of 200 to 300 W, and the silicon substrate at the resist opening is etched to form a shallow groove 105.

Then, as shown in FIG.
A silicon oxide film 106 is deposited by the method.

Thereafter, as shown in FIG. 1E, the silicon oxide film is etched by a dry etching method at a pressure of several Torr using an etching gas of CHF ₃ to form a side wall 107 at the end of the silicon nitride film 103. .

Next, as shown in FIG. 1F, N (nitrogen) ions are implanted at a dose of 10 ¹⁴ cm ⁻² to 10 ¹⁵ cm ⁻² or more. Thereby, a side wall 107 'of the silicon oxide film containing N (nitrogen) and a silicon substrate region 109 are formed.

Then, as shown in FIG. 1 (g), the silicon substrate containing nitrogen on the surface parallel to the wafer surface is etched by dry etching at a pressure of several Torr using an etching gas of CHF _3. And shallow groove 1
Form 10.

Then, as shown in FIG. 1H, using the silicon nitride film 103 and the side wall 107 'as a mask,
A thick oxide film 111 is formed as a field oxide film by wet oxidation, dry oxidation, or a combination of wet oxidation and dry oxidation at a temperature of 000 ° C. to 1150 ° C.

Subsequently, as shown in FIG. 1I, a thin silicon oxide film formed on the silicon nitride film before removing the silicon nitride film, the upper portion of the field oxide film and the side wall 10 are formed.
7 'is etched with a solution containing hydrofluoric acid. The amount of etching is such that the side wall 107 'is completely removed. Then, the silicon nitride film 1 is heated with hot phosphoric
03 and the side wall 107 'are etched.

Thereafter, a normal process is performed to form a MIS transistor.

The element isolation region thus formed can open a narrower region than the limit of the photolithography technique only by the width of the side wall, so that miniaturization is possible.

In the field oxide film formation step, N (nitrogen) injected into the side wall suppresses the entry of oxygen as an oxidant, so that the bird's beak is shortened.

Next, FIG. 2 will be described. FIG. 2 (a)
In order to form an element isolation region, a pad oxide film for relaxing stress is formed on a wafer of a silicon substrate 201 by thermal oxidation in an oxygen atmosphere at 800 ° C. to 1100 ° C. or in a steam atmosphere as shown in FIG. Å to 300
A silicon oxide film 202 having a thickness of Å is grown.

Next, the entire surface of the wafer is 800
A silicon nitride film 203 having a thickness of {2000} is deposited. Then, after a resist film 204 is applied over the entire surface of the wafer, a region where a field oxide film is to be formed is selectively opened by photolithography.

Next, as shown in FIG. 2B, CH ₄ or CH ₄ is applied by a dry etching method under a pressure of several hundred mTorr.
The silicon nitride film in the resist opening is etched using an O ₂ etching gas.

Further, as shown in FIG. 2C, the silicon oxide film is etched by dry etching using a CHF ₃ etching gas under a pressure of several Torr.
By dry etching, C under a pressure of several hundred mTorr
Plasma is generated with an F ₄ etching gas at a flow rate of several tens of cc / min and RF power of 200 to 300 W, and the silicon substrate at the resist opening is etched to form a shallow groove 205.

Then, as shown in FIG.
A polysilicon oxide film or an amorphous silicon film 206 is deposited by the method.

Thereafter, as shown in FIG.
Using a mixed gas of Cl ₂ and O ₂ , etching is performed under a pressure of several mTorr to etch the polysilicon oxide film or the amorphous silicon film 206 to form a sidewall 207 at an end of the silicon nitride film 203. Next, FIG.
As shown in (f), N (nitrogen) ions are introduced at 10 ¹⁴ cm ^-2 or ^less .
Implant at a dose of 10 ¹⁵ cm ^-2 or more. Thereby N
The silicon substrate region 209 and the side wall 207 ′ of the polysilicon oxide film or the amorphous silicon film 206 containing (nitrogen) are formed.

Then, as shown in FIG. 2 (g), the silicon substrate containing nitrogen on the surface parallel to the wafer surface is etched by dry etching using a CHF ₃ etching gas under a pressure of several Torr. And shallow groove 2
Form 10.

Then, as shown in FIG. 2H, using the silicon nitride film 203 and the side walls 207 'as a mask,
A thick oxide film 210 is formed as a field oxide film by wet oxidation, dry oxidation, or a combination of wet oxidation and dry oxidation at a temperature of 000 ° C. to 1150 ° C. At this time, the side wall 207 'is also oxidized to become a silicon oxide film.

Subsequently, as shown in FIG. 2I, a thin silicon oxide film formed on the silicon nitride film before removing the silicon nitride film, the upper portion of the field oxide film and the side wall 20 are formed.
7 'is etched with a solution containing hydrofluoric acid. The amount of etching is such that the side wall 207 'is completely removed. Then, the silicon nitride film 2 is heated with hot phosphoric
03 and the side wall 207 'are etched.

Thereafter, a normal process is performed to form a MIS transistor.

In the element isolation region formed in this way, a narrower region than the limit of the photolithography technique can be opened by the side wall width, and miniaturization is possible.

In the field oxide film formation step, N (nitrogen) injected into the side wall suppresses the entry of oxygen as an oxidant, so that the bird's beak is shortened.

Further, since the side wall is a polysilicon oxide film or an amorphous silicon film, the stress between the silicon oxide film formed thereunder and the silicon substrate is reduced.

[0051]

As described above, the present invention has the following effects.

Since the device isolation region formed in this manner oxidizes the region where the silicon substrate is etched, the uppermost part of the field oxide film made of the silicon oxide film which is raised by the oxidation reaction is higher than in the conventional device. Lower to the surface.

Therefore, a flat shape can be obtained. Further, also at the side wall of the silicon nitride film as a mask of the antioxidant film at the time of forming the field oxide film, the layer in which N (nitrogen) is mixed acts as the antioxidant film, so that the bird's beak can be suppressed from growing.

Therefore, according to the above technique, it is possible to obtain a flat wafer shape and to suppress the bird's beak from growing. As an effect thereof, it is possible to prevent a problem when using a photolithography technique in a later step and prevent a device formation region from being narrowed. Further, when a polysilicon oxide film or an amorphous silicon film is used for the side wall, there is an effect that stress applied to the silicon substrate is small.

Accordingly, it is possible to provide a method of manufacturing a semiconductor device which has high accuracy in manufacturing the semiconductor device, and which can be miniaturized with high quality.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a wafer along a process order of a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view of a wafer along a process sequence of a method of manufacturing a semiconductor device according to the present invention.

FIG. 3 is a cross-sectional view of a wafer along a process sequence of a conventional method for manufacturing a semiconductor device.

FIG. 4 is a cross-sectional view of a wafer along a process sequence of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

101, 201, 301, 401 Silicon substrate 102, 202, 302, 402 Silicon oxide film 103, 203, 303, 403 Silicon nitride film 104, 204, 304, 404 Resist 105, 205, 305 Groove 106 in field oxidation planned region CVD silicon oxide film 206 CVD polysilicon film or amorphous silicon film 107 Side wall of silicon oxide film 207 Side wall of CVD polysilicon film or amorphous silicon film 107 ′ Side wall of silicon oxide film mixed with nitrogen 207 ′ CVD mixed with nitrogen Side walls 108, 208 N (nitrogen ions) 109, 208, 405 of polysilicon film or amorphous silicon film Silicon substrate 406 mixed with nitrogen Silicon oxide film 110, 210, 407 mixed with nitrogen 111, 211, 306, 408 Field oxide film formed by etching the portion in which is mixed

Claims (3)

[Claims] A step of selectively providing an antioxidant film on a silicon substrate via a pad oxide film in a step of forming a field oxide film; and a step of removing the pad oxide film in a region where the antioxidant film is opened. Etching a silicon substrate to form a groove; oxidizing the silicon substrate in the opening to form a silicon oxide film; providing a side wall in the groove; A method for manufacturing a semiconductor device, comprising: a step of implanting; a step of removing a silicon oxide film at a bottom portion of the groove; and a step of oxidizing using a side wall of the groove and the antioxidant film as a mask. 2. The method of manufacturing a semiconductor device according to claim 1, wherein in the step of providing a side wall on the oxidation preventing film, the side wall is formed of a silicon oxide film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein in the step of providing a side wall on the oxidation preventing film, the side wall is formed of a polysilicon film or an amorphous silicon film.