JPH1187336A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress bird's beak formation and form a field oxide film, by forming an oxidation-resistant film on the surface of a semiconductor substrate for opening an oxide film forming region and generating a crystal defect in the semiconductor substrate especially by implanting impurity ions. SOLUTION: A thin oxide film 2 is formed on the surface of a semiconductor substrate 1 which is composed of silicon single crystal. A nitride film 3 to be an oxidation-resistant film is formed on the oxide film 2. A photoresist film 4 is patterned on the nitride film 3 so as to open an oxide film forming region. The photoresist film 4 is used as the etching mask, the nitride film 3 in the oxide film forming region is removed and the thin oxide film 2 is exposed. Then, argon ions are implanted through the exposed thin oxide film 2. A crystal defect is generated in the semiconductor substrate 1 by the ion implantation. Then, the photoresist film 4 is removed, heat treatment is performed in the atmosphere that contains oxygen and nitrogen, and a field oxide film 5 is formed on the surface of the semiconductor substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a thick oxide film (field oxide film) for element isolation.

[0002]

2. Description of the Related Art When a semiconductor device such as a bipolar transistor or a MOS transistor is formed on a semiconductor substrate made of silicon single crystal, a thick oxide film for element isolation is previously formed by using a selective oxidation method around an element forming region. A film (field oxide film) is formed.

A conventional field oxide film is formed as follows. First, a thin oxide film 2 is formed on the surface of a semiconductor substrate 1 made of silicon single crystal by a thermal oxidation method, and a nitride film 3 is deposited on the thin oxide film 2 over the entire surface. Next, a photoresist film 4 is patterned on the nitride film 3 so as to open a field oxide film formation region (FIG. 4). Using the photoresist film 4 as an etching mask, the nitride film 3 in the opening is removed by etching to expose the thin oxide film 2 (FIG. 5). After removing the photoresist film 4, thermal oxidation is performed using the nitride film 3 as an oxidation-resistant film. As a result, a thick field oxide film 5 is formed at the opening of nitride film 3 (FIG. 6).

[0004]

In such a manufacturing method, an oxide film grows in the horizontal direction (lateral direction) simultaneously with the growth of the oxide film in the vertical direction (depth direction) with respect to the surface of the semiconductor substrate. I do. The oxide film grown in the horizontal direction is called a bird's beak, and has hindered miniaturization.

As a method of reducing bird's beak, for example, a method of increasing the thickness of a nitride film used as an oxidation resistant film has been proposed. However, a nitride film has a large stress at the time of formation, and when the film thickness is increased, the stress applied to the silicon substrate increases, and there is a problem that defects such as dislocations are generated. could not. Therefore, the formation of bird's beak could not be effectively suppressed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a semiconductor device which solves the above problems, suppresses the formation of bird's beaks, and can form a field oxide film.

[0007]

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising forming an oxide film on a predetermined region of a surface of a semiconductor substrate made of silicon single crystal. Forming an oxidation-resistant film that opens the oxide film-forming region; generating crystal defects in the semiconductor substrate in the opening; and heat-treating the semiconductor substrate to form a surface in the opening. Forming an oxide film that has grown thicker in the vertical direction than in the horizontal direction.

In particular, by implanting impurity ions, specifically, silicon and argon, a crystal defect can be easily generated in the semiconductor substrate, and a field oxide film in which the formation of bird's beaks is suppressed is formed. It becomes possible.

[0009]

Embodiments of the present invention will be described below. First, a semiconductor substrate 1 made of a silicon single crystal whose surface has been cleaned is prepared. A heat treatment is performed at about 900 to 1000 ° C. in an atmosphere containing oxygen and hydrogen to form a thin oxide film 2 having a thickness of about 200 Å on the surface of the semiconductor substrate 1.

On the thin oxide film 2, a nitride film 3 serving as an oxidation-resistant film is formed to a thickness of 1000 angstroms by a normal CVD method. A photoresist film 4 is patterned on the nitride film 3 so as to open a region where a field oxide film is to be formed (FIG. 1). Using the photoresist film 4 as an etching mask, the nitride film 3 in the region where the field oxide film is to be formed is removed, exposing the thin oxide film 2.

Here, through the exposed thin oxide film 2,
Acceleration energy 80 KeV, injection amount 1 × 10 16 atom
/ Cm 2, argon ions are implanted (FIG. 2). Due to this ion implantation, crystal defects occur in the portion of the semiconductor substrate 1 indicated by the broken line in FIG.

Thereafter, the photoresist film 4 is removed, and a heat treatment is performed at about 900 to 1000 ° C. for 44 minutes in an atmosphere containing oxygen and nitrogen, so that a thickness of 2000
A field oxide film 5 of about Å is formed (FIG. 3).

For comparison, when an oxide film is formed without performing ion implantation under the above-described conditions for forming a field oxide film 5 having a thickness of 2000 Å, the thickness of the field oxide film becomes 1600 Å.

In this case, comparing the growth rate of the oxide film in the depth direction of the two, the conventional method is 36.4 Å / min, whereas the present invention is 45.5 Å / min. Shows that an oxide film can be formed in a short time. On the other hand, the region where the bird's beak is formed is a portion where no crystal defects occur,
The growth rate is almost the same in both the present invention and the conventional method, and is proportional to the oxidation time. Therefore, when a field oxide film having the same thickness is formed, the bird's beak is less formed in the present invention which ends with a short heat treatment.

If it is possible to generate a crystal defect in the field oxide film forming region of the semiconductor substrate 1, it is possible to variously change the ion implantation conditions according to the thickness of the thin oxide film 2 and the like. It is. However, after a crystal defect is generated only in the vicinity of the surface, when heat treatment is performed for a relatively long time, when ion implantation is performed and when ion implantation is not performed,
In some cases, a large difference in the growth rate of the oxide film disappears. Therefore, when the thickness of the field oxide film to be formed is large, it is necessary to set ion implantation conditions so that crystal defects occur at deep positions.

The above description has been made taking the case where argon ions are implanted as an example, but the present invention is not limited to this.
It has been confirmed that even when silicon ions are implanted, a field oxide film with little bird's beak can be formed. Also in this case, it is needless to say that silicon ions need to be implanted under conditions that cause crystal defects in the semiconductor substrate.

Also, a case has been described where a nitride film formed on a thin oxide film is used as the oxidation resistant film.
The present invention is not limited to this, and various changes can be made.

[0018]

As described above, according to the present invention,
The time for thermal oxidation can be shortened, and as a result, the formation of bird's beaks can be reduced, and the effect of miniaturizing the semiconductor element can be achieved.

Further, since it is not necessary to form a thick nitride film and the time for thermal oxidation can be shortened, no crystal defects are generated in the semiconductor substrate in the element formation region. There is also an effect that it can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating an embodiment of the present invention.

FIG. 3 is a diagram illustrating an embodiment of the present invention.

FIG. 4 is a diagram illustrating a conventional process of forming a field oxide film.

FIG. 5 is a diagram illustrating a conventional process of forming a field oxide film.

FIG. 6 is a view for explaining a conventional step of forming a field oxide film.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor substrate 2 thin oxide film 3 nitride film 4 photoresist film 5 field oxide film

Claims (3)

[Claims] 2. A method for manufacturing a semiconductor device, comprising: forming an oxide film on a predetermined region of a surface of a semiconductor substrate made of silicon single crystal; Performing a crystal defect in the semiconductor substrate in the opening; and performing a heat treatment on the semiconductor substrate to form a crystal defect in the opening.
Forming an oxide film that has grown thicker in the vertical direction than in the horizontal direction on the surface of the semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a crystal defect is generated in the semiconductor substrate by implanting impurity ions. 3. The method for manufacturing a semiconductor device according to claim 2, wherein said impurity is argon or silicon.