JPH0714827A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the generation of a crystal defect in a semiconductor wafer by a method wherein the semiconductor wafer with a boron impurity layer formed therein is heat-treated in a nitrogen gas atmosphere and thereafter, an oxidation treatment is performed on the wafer in an oxidizing atmosphere. CONSTITUTION:A nitrogen annealing oxidizing process 15 is performed on a silicon wafer, from which a boron glass layer is removed by a boron deposition process 10 and a boron glass layer removal process 11. In such a way, the wafer with a boron impurity layer formed therein is heat-treated in a nitrogen gas atmosphere, whereby as a microscopic crystal defect, which is induced by a contaminant from a baron silicide layer, is diffused outside of the wafer, the generation of a crystal defect, which is induced in a thermal oxidation process, can be inhibited. As the heat treatment in the nitrogen gas atmosphere and a heat treatment in an oxidizing atmosphere are continuously performed in the same treating furnace, a process for removing the boron silicide layer can be omitted.

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 technique effectively applied to a method for forming a semiconductor region and a thermal oxide film on the surface of a silicon (Si) wafer.

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing a semiconductor wafer of the type in which boron is diffused in a silicon wafer to form a boron diffusion region and thermal oxidation is formed on the surface thereof has been performed by the steps shown in FIG. This conventional technique will be described while comparing the working steps shown in FIG. 4 with the sectional views of the silicon wafer in the steps shown in FIGS. 5 to 9 and the heat treatment sequence shown in FIG.

In FIG. 4, a boron deposition process 1
When 0 is performed, as shown in FIG. 5, a boron deposition layer 2 is formed in the silicon wafer 1, a boron silicide layer 3 is formed thereon, and further a boron glass layer 4 is formed thereon. It

When the step 11 of removing the boron glass layer 4 is performed by a hydrofluoric acid (HF) -based etch, as shown in FIG.
Although the boron glass layer 4 is removed, the boron silicide layer 3 insoluble in the hydrofluoric acid (HF) -based solution remains.

Next, this is taken into the light oxide film 5 which is heat-treated in an oxidizing atmosphere at 8800 ° C. Further, a light oxide film removing step 13 using a hydrofluoric acid (HF) -based solution 13
Then, as shown in FIG. 8, the light oxide film 5 is removed.

An oxidation diffusion step 14, that is, a heat treatment sequence shown in FIG. 10 is performed on such a silicon wafer 1. That is, the silicon wafer 1 shown in FIG.
The temperature is raised at a rate of 5 ° C per minute for about 40 minutes. 100
After 180 minutes at 0 ° C, the temperature is lowered to 800 ° C in about 67 minutes at a rate of 3 ° C per minute.

By this oxidation diffusion step 14, as shown in FIG. 9, the boron deposition layer 2 is stretched (diffused) to form a boron diffusion layer 6 and a thermal oxide film 7 on the surface of the silicon wafer 1. It is formed.

[0008]

However, as a result of examining the above-mentioned prior art, the present inventor found the following problems.

In the above-mentioned prior art, the boron silicide layer 3
Is a layer in which pollutants such as heavy metals are gathered by the getter effect by the boron deposition process. Therefore, in the light oxidation step 12, there is a problem that due to the diffusion effect of the heat treatment, some of the contaminants are released into the silicon wafer 1 and diffused, and crystal defects are easily induced by the subsequent oxidation treatment. The presence of this crystal defect causes a characteristic defect as a semiconductor product such as a leakage current defect.

An object of the present invention is to provide a technique capable of preventing the occurrence of crystal defects.

Another object of the present invention is to provide a technique capable of omitting a part of the manufacturing process.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0013]

The typical ones of the inventions disclosed in the present application will be outlined below.

(1) In a method for manufacturing a semiconductor device in which a boron impurity layer is formed on a semiconductor wafer and a thermal oxide film is formed on the boron impurity layer, the semiconductor wafer having the boron impurity layer formed is placed in a nitrogen gas atmosphere. After the heat treatment is performed in step 1, an oxidation process is performed in an oxidizing atmosphere to form an oxide film on the surface of the semiconductor wafer.

(2) The heat treatment in the nitrogen gas atmosphere and the heat treatment in the oxidizing atmosphere are continuously performed in the same processing furnace.

[0016]

According to the above-mentioned means, the semiconductor wafer on which the boron impurity layer is formed is heat-treated in a nitrogen gas atmosphere, so that fine crystal defects induced by contaminants from the boron silicide layer are removed from the wafer. Since it is diffused (annealed out), it is possible to suppress the generation of crystal defects induced in the thermal oxidation treatment.

Since the heat treatment in the nitrogen gas atmosphere and the heat treatment in the oxidizing atmosphere are continuously performed in the same processing furnace,
Part of the manufacturing process can be omitted.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a flow chart for explaining a step of forming a surface oxide film on a semiconductor wafer in an embodiment of a method for manufacturing a semiconductor device of the present invention.

In FIG. 1, boron deposition step 1
Since 0 and the boron glass layer removing step 11 are the same as those in the prior art, the description thereof is omitted here.

By the boron deposition step 10 and the boron glass layer removing step 11, the silicon wafer from which the boron glass layer shown in FIG. 6 is removed can be obtained.

Next, a nitrogen annealing oxidation (diffusion) step 15 is performed on the silicon wafer from which the boron glass layer has been removed. Details of this step 15 will be described with reference to FIG. 2 (nitrogen annealing oxidation / diffusion processing sequence).

In FIG. 2, the silicon wafer from which the boron gas layer has been removed is placed in a furnace having a nitrogen (N ₂ ) atmosphere,
The temperature is raised from 0 ° C to 1000 ° C at a rate of 5 ° C per minute for 40 minutes. When the temperature reaches 1000 ° C., 60 minutes after the temperature is maintained, the temperature in the furnace is maintained at 1000 ° C. and the nitrogen (N ₂ ) atmosphere is changed to the wet oxygen (O ₂ ) atmosphere for 180 minutes. Thereafter, the temperature is lowered to 800 ° C. at 67 ° C. at a rate of 3 ° C./min.

In the nitrogen anneal oxidation (diffusion) step 15, the temperature of the nitrogen anneal treatment may be set to 900 ° C., as shown in FIG. Whether the temperature of the nitrogen annealing treatment is 900 ° C. or 1000 ° C. may be selected according to the process design specifications such as the diffusion depth.

As described above, by heat-treating the silicon wafer on which the boron impurity layer is formed in a nitrogen gas atmosphere, fine crystal defects induced by contaminants from the boron silicide layer diffuse out of the silicon wafer ( Since it is annealed out, it is possible to suppress the generation of crystal defects induced in the thermal oxidation treatment.

Since the heat treatment in the nitrogen gas atmosphere and the heat treatment in the oxidizing atmosphere are continuously performed in the same processing furnace,
It is possible to omit the light oxidation treatment process and the light oxide film removal process for removing the boron silicide layer.

In the above-mentioned embodiment, the nitrogen annealing treatment is performed before the oxidation treatment, but the opposite effect can also be obtained.

Further, in the above-mentioned embodiment, the nitrogen annealing treatment and the oxidizing treatment are continuously carried out in the same furnace, but a considerable effect can be obtained even if they are carried out in another furnace.

Although the present invention has been specifically described based on the embodiments, it is needless to say that the present invention is not limited to the above embodiments and can be variously modified without departing from the scope of the invention. Nor.

[0030]

The effects obtained by the typical ones of the disclosed inventions in this application will be briefly described as follows.

(1) The occurrence of crystal defects can be prevented.

(2) Part of the manufacturing process can be omitted.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining a surface oxide film forming step of a semiconductor wafer in an embodiment of a method for manufacturing a semiconductor device of the present invention,

FIG. 2 is a diagram showing a heat treatment sequence of the silicon wafer of the present embodiment,

FIG. 3 is a diagram showing another heat treatment sequence of the silicon wafer of the present embodiment,

FIG. 4 is a flowchart for explaining a conventional process for forming a surface oxide film on a semiconductor wafer,

FIG. 5 is a sectional view of a semiconductor wafer after the conventional boron deposition process is completed,

FIG. 6 is a cross-sectional view of a semiconductor wafer after the conventional boron glass layer removal step,

FIG. 7 is a cross-sectional view of a semiconductor wafer after the conventional light oxidation step is completed.

FIG. 8 is a cross-sectional view of a semiconductor wafer after a conventional light oxide film removal step is completed,

FIG. 9 is a cross-sectional view of a semiconductor wafer after a conventional oxidation (diffusion) step is completed,

FIG. 10 is a diagram showing a heat treatment sequence of a conventional semiconductor wafer.

[Explanation of symbols]

1 ... Silicon wafer, 2 ... Boron deposition layer, 3
... Boron silicide layer, 4 ... Boron glass layer, 5 ... Light oxide film, 6 ... Boron diffusion layer, 7 ... Thermal oxide film, 10 ... Boron deposition step, 11 ... Boron glass layer removal step, 12 ... Light oxidation step, 13 ... Light oxide film removal step, 14 ... Oxidation (diffusion) step, 15 ... Nitrogen annealing oxidation (diffusion) step.

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device, wherein a boron impurity layer is formed on a semiconductor wafer and a thermal oxide film is formed on the boron impurity layer, wherein the semiconductor wafer having the boron impurity layer is formed in a nitrogen gas atmosphere. After heat treatment,
A method of manufacturing a semiconductor device, comprising: forming an oxide film on a surface of a semiconductor wafer by performing an oxidation treatment in an oxidizing atmosphere. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment in the nitrogen gas atmosphere and the heat treatment in an oxidizing atmosphere are continuously performed in the same processing furnace. Method.