JPH07326610A - Forming method of element isolation region of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a forming method of an element isolation region of a semiconductor device which makes it possible to form the element isolation region excellently and also to realize shortening of a process. CONSTITUTION:In a forming method of an element isolation region of a semiconductor device wherein the element isolation region 2 is formed on a semiconductor substrate 1, the element isolation region is formed by using a selective oxidation method wherein only a single layer of a silicon oxi-nitride film 3 formed on the semiconductor substrate is made a mask. A bird's beak amount of the element isolation region is regulated by the contents of oxigen and nitrogen in the silicon oxi-nitride film 3, as occasion demands.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an element isolation region of a semiconductor device. INDUSTRIAL APPLICABILITY The present invention can be used as a method for forming an element isolation region in various semiconductor devices, for example, a method for forming an element isolation region in manufacturing an integrated semiconductor circuit such as a highly finely integrated memory device. .

[0002]

2. Description of the Related Art Conventionally, a selective oxidation method is often used for element isolation of a semiconductor device. For example, as shown in FIG. 2A, a semiconductor substrate 1 (Si substrate in the figure) is used. Upper pad oxide film 1a (usually Si
O ₂ ) and a nitride film 1b (usually Si ₃ N ₄ ) are used to perform oxidation to form an oxide film forming an element isolation region 2 as shown in FIG. 2B. (LOCOS method or the like for a silicon semiconductor device) has been used.

By the way, in recent years, in order to reduce the cost, further shortening of the process is desired.

However, in order to shorten the process, as shown in FIG. 3, except for the pad oxide film forming process, the nitride film 1b (see FIG.
If only (a)) is used as a mask, bird's beaks are reduced, but large stress concentrates on the interface between the oxide film and the active region (active layer) indicated by the symbol A in FIG. However, the junction leakage current tends to increase.

On the other hand, as shown in FIG. 4, when only the oxide film 1d as shown in FIG. 4A is used as a mask except for the step of forming a nitride film, it is oxidized with the masked film (oxide film 1d). since both of the resulting film (element isolation region 2 ') is SiO _2, when etching the mask film oxidized will be removed, it is impossible to form an element isolation region.

The stress concentration, which is a problem when using only the above-mentioned nitride film as a mask, has a trade-off relationship with the elongation of the bird's beak, and if the film thickness increase during the growth of the oxide film is forcibly suppressed, a large stress occurs. Since concentration occurs, the stress is relieved by growing some bird's beaks. The bird's beak elongation has been optimized mainly by the pad oxide film thickness, the nitride film thickness, and the film thickness ratio of the two. Therefore, a mask having a two-layer structure is necessary, and eventually, the number of steps cannot be reduced.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for forming an element isolation region of a semiconductor device, which can solve the problems of the above-mentioned prior art and can form an element isolation region satisfactorily and also can shorten the process. With the goal.

[0008]

The invention according to claim 1 of the present application is a method of forming an element isolation region of a semiconductor device, which comprises forming an element isolation region on a semiconductor substrate, the method comprising the step of forming a silicon oxide on a semiconductor substrate. A method for forming an element isolation region of a semiconductor device, characterized by forming the element isolation region using a selective oxidation method using only a single layer of a nitride film as a mask, which solves the above problems. is there.

According to a second aspect of the present invention, the bird's beak amount in the element isolation region is adjusted by adjusting the oxygen and nitrogen contents in the silicon oxynitride film. The method for forming the element isolation region is to solve the above problems.

[0010]

According to the present invention, since the silicon nitride film is used as the mask material, it has both the effect of the pad oxide film and the effect of the nitride film. By using a silicon oxynitride film single layer as a mask material, the process can be shortened. As described above, the present invention is a method of forming an element isolation region using a selective oxidation method using only a single layer of a silicon oxynitride film as a mask, whereby no large stress concentration occurs, and bird's beaks have the same degree as the conventional method. The element isolation can be performed by reducing the number of steps.

Further, according to the present invention, the elongation of the bird's beak can be controlled by adjusting the content ratio of oxygen and nitrogen in the silicon oxynitride film, and the amount of bird's beak can be adjusted accordingly.

According to the present invention, in a semiconductor device such as SRAM or ASIC, a pad oxide film forming step, a pretreatment step therefor and a pad oxide film removing step can be omitted, and the steps can be shortened and the cost can be reduced. It can also have an effect.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. However, as a matter of course, the present invention is not limited to the examples described below.

Example 1 In this example, the present invention is applied to the formation of an element isolation region of a silicon semiconductor device such as SRAM or ASIC.

This embodiment is shown in FIG. In this embodiment, a device isolation region 2 (see FIG. 1) is formed on a semiconductor substrate (here, a Si substrate).
(B)) is a method of forming an element isolation region of a semiconductor device, which comprises a selective oxidation method using only a silicon oxynitride film single layer formed on a semiconductor substrate 1 shown in FIG. 1A as a mask. It is used to form the element isolation region.

In this embodiment, the bird's beak amount in the element isolation region is adjusted by adjusting the oxygen and nitrogen contents in the silicon oxynitride (SiO _x N _y ) film.

The process of this embodiment will be described in more detail below. In this embodiment, as shown in FIG. 1A, a silicon oxynitride film 3 is formed on a bare Si substrate which is the semiconductor substrate 1. An example of the film forming conditions (condition 1) at this time is shown below.

Condition 1 Apparatus LPCVD apparatus Gas SiH ₂ Cl ₂ = 50 sccm, NH ₃ = 20
0 sccm, N ₂ O = 5 sccm Pressure 70 Pa Temperature 760 ° C.

In this example, the contents of oxygen and nitrogen in the silicon oxynitride film were controlled. This control can be performed using, for example, the amount of N ₂ O added as a parameter. That is, since the proportion of oxygen contained increases as the amount of N ₂ O added increases, the content of oxygen and nitrogen in the silicon nitride film can be controlled by utilizing this.

After the silicon oxynitride film is formed, the photoresist is patterned and the silicon oxynitride is selectively removed by RIE. As a result,
As shown in (a), a patterned silicon oxynitride film 3 is obtained. In the present invention, since the silicon oxynitride film is used as a mask for preventing oxidation, it is generally preferable that the nitrogen content ratio be higher than that of the silicon oxynitride film under normal forming conditions. This embodiment has such a condition. Therefore, the etching conditions (here, RIE conditions) may be the same as the RIE conditions for the silicon oxynitride film.

After removing the photoresist, selective oxidation is performed using the single layer of silicon nitride film 3 as a mask, and then the silicon oxynitride film 3 is removed by hot phosphoric acid. From the above, the element isolation region 2 shown in FIG.
Can be formed.

According to the present embodiment, in the semiconductor device such as SRAM and ASIC, the element isolation region can be formed well, and the conventional pad oxide film forming step and the pretreatment step and pad oxide film removing step therefor. Can be reduced, the process can be shortened, and the cost can be reduced.

Example 2 In this example, the element isolation region was formed in the same manner as in Example 1, but here, in forming the silicon oxynitride film,
The following conditions (condition 2) were used.

Condition 2 Apparatus LPCVD gas SiH ₄ = 50 sccm, NH ₃ = 200 sc
cm, N ₂ = 2000 sccm, N ₂ O = 5 sccm Pressure 70 Pa Temperature 760 ° C.

In this embodiment, the oxygen and nitrogen contents in the silicon oxynitride film may be controlled by using the amount of N ₂ O added as a parameter, as in the condition 1 of the first embodiment. Similarly, the greater the amount of N ₂ O added, the greater the proportion of oxygen contained.

In this embodiment, the same effect as that of the first embodiment can be obtained.

[0027]

As described above, according to the present invention, it is possible to provide a method for forming an element isolation region of a semiconductor device, which can form an element isolation region satisfactorily and also can shorten the process.

[Brief description of drawings]

FIG. 1 shows steps of Example 1 of the present invention.

FIG. 2 is a diagram showing a conventional technique.

FIG. 3 is a diagram showing a problem.

FIG. 4 is a diagram showing a problem.

[Explanation of symbols]

 1 semiconductor substrate 2 silicon oxynitride 3 element isolation region (oxide film)

Claims (2)

[Claims] 1. A method of forming an element isolation region of a semiconductor device, wherein an element isolation region is formed on a semiconductor substrate, using a selective oxidation method using only a silicon oxynitride film single layer formed on a semiconductor substrate as a mask. A method for forming an element isolation region of a semiconductor device, which comprises forming an element isolation region by means of the above method. 2. The method for forming an element isolation region of a semiconductor device according to claim 1, wherein the bird's beak amount of the element isolation region is adjusted by adjusting the contents of oxygen and nitrogen in the silicon oxynitride film.