JP3282265B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a step of diffusing impurities in a semiconductor manufacturing process .
It relates to a manufacturing method.

[0002]

2. Description of the Related Art As an example of a conventional method of forming a high-concentration P-type impurity layer, boron is introduced as an impurity into a silicon substrate by ion implantation, and heat treatment is performed to diffuse the introduced boron to obtain a high-concentration P-type impurity layer. A method for forming a P-type impurity layer has been proposed. In this method, a defect such as a crystal defect occurs in the region where the ion is implanted, so that a junction leak occurs in that portion. In order to prevent the above defects from occurring, a method has been proposed in which a diffusion treatment is performed using a high-concentration BSG film (for example, a film having a boron concentration of 4.5 w%) as a diffusion source.

Next, a diffusion process using the high-concentration BSG film will be described with reference to FIG. As shown in FIG. 6A, an oxide film 62 is formed on the surface of the silicon substrate 61 by a normal oxidation method. Next, the oxide film 62 (the portion indicated by the two-dot chain line) on the region 63 where the diffusion layer is to be formed on the silicon substrate 61 is removed by ordinary photolithography and etching. Thereafter, a high-concentration BSG film 64 is formed by, for example, a chemical vapor deposition method. The high concentration BSG film 64 contains, for example, 4.5 w% of boron.

[0006] Then, as shown in FIG. 6 (2), for example, a high-temperature diffusion process is performed in a nitrogen atmosphere to diffuse boron in the high-concentration BSG film 64 into the upper layer of the silicon substrate 61.
A high concentration boron diffusion layer 65 is formed. The diffusion temperature at this time is set to, for example, 1200 ° C. In the diffusion process, a nitride film 66 is formed on the back surface of the silicon substrate 61.

[0005]

However, when the above-described diffusion treatment using the high-concentration BSG film is performed in an oxygen atmosphere, an oxide film grows at the interface between the silicon substrate and the high-concentration BSG film, and the oxide film grows. The film prevents boron diffusion. Further, when the above-described diffusion treatment is performed in a nitrogen atmosphere, boron precipitates at the interface between the silicon substrate and the high-concentration BSG film, and the surface of the silicon substrate becomes hydrophilic. In this state, when, for example, a wet process is performed, foreign matter easily adheres to the hydrophilic surface, so that foreign matter adheres to the silicon substrate, thereby lowering the cleanliness of the silicon substrate. When heat treatment is performed, out diffusion due to boron occurs, and the silicon substrate is contaminated with boron. Further, since a nitride film is formed on the back surface side of the silicon substrate, the nitride film peels off during wet processing, for example, and causes dust. All of the above problems will reduce the yield.

[0006] The present invention is excellent in cleanliness, carry out the diffusion of impurities so that there is no occurrence of the out-diffusion
It is an object to provide a method for manufacturing a semiconductor device .

[0007]

SUMMARY OF THE INVENTION The present invention is a method for manufacturing a semiconductor device which has been made to achieve the above object. That is, in the first step, after forming a diffusion prevention mask on the surface of the silicon-based substrate except for the surface of the diffusion region of the silicon-based substrate, a film containing impurities is formed on at least the surface of the diffusion region, In the second step, an oxide film having a thickness smaller than that of the diffusion prevention mask is formed at least on a surface layer of the diffusion region. Thereafter, in a third step, the impurities in the film containing the impurities are diffused into the diffusion region through the thin oxide film by a thermal diffusion process to form an impurity diffusion layer .
Semiconductor device for wet-treating the silicon-based substrate in a process
It is a manufacturing method of the device. Alternatively, after performing the first step, in a second step, an oxide film having a thickness smaller than that of the diffusion prevention mask is formed on the surface layer of the diffusion target region and the back surface of the silicon-based substrate. Is a method for manufacturing a semiconductor device .

The thermal oxidation treatment is performed at an oxidizable temperature of 900 ° C. or less, for example, in an inert gas atmosphere containing oxygen, and the thermal diffusion treatment is performed in an inert gas atmosphere.
This is performed at an arbitrary temperature in a temperature range of 050 ° C. to 1250 ° C.

In the first step, after forming a diffusion prevention mask on the surface of the silicon-based substrate except for the surface of the diffusion region of the silicon-based substrate, at least the surface of the diffusion region is formed.
Forming an oxide film thinner than the diffusion prevention mask ;
In this step, a film containing impurities is formed on at least the surface of the thin oxide film. Thereafter, in a third step, the impurities in the film containing the impurities are diffused into the diffusion region through the thin oxide film by a thermal diffusion process to form an impurity diffusion layer .
In a fourth step, a half of the silicon-based substrate is wet-processed .
It is a manufacturing method of a conductor device . Or in the first step, after forming the diffusion preventing mask on a surface of the silicon substrate except the surface of the diffusion region of the silicon substrate, preventing the diffusion into the surface layer and the back surface of the silicon substrate of the diffusion region Ma
An oxide film having a thickness smaller than that of the mask is formed, and then the second step and the third step are performed.

In each of the above-described methods for manufacturing a semiconductor device , a thin oxide film is formed with a thickness of 1 nm to 10 nm.

[0011]

In the method of manufacturing a semiconductor device , before performing the thermal diffusion process, the thickness of the diffusion prevention mask is set on the surface of the diffusion target region.
By was formed a thin oxide film, for example BS as a film containing, for example, silicon substrate and the impurity as the diffusion region
Boron does not precipitate at the interface with the G film. As a result, the hydrophobicity of the surface of the diffusion region is maintained. Further, since a thin oxide film is formed on the back surface of the silicon-based substrate, no silicon nitride film is formed on the back surface of the silicon-based substrate during the thermal diffusion process. Since the thin oxide film is formed to a thickness of 1 nm to 10 nm, the impurities diffuse from the film containing the impurities into the diffusion region without being hindered by the thin oxide film during the thermal diffusion process. Is not formed with a silicon nitride film.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to a diffusion step diagram of FIG. As shown in FIG. 1A, in a first step, a silicon oxide film 12 is formed on the surface of a silicon-based substrate 11 by, for example, a normal chemical vapor deposition method.
Next, the silicon oxide film 12 (the portion indicated by the two-dot chain line) on the diffusion region 13 is removed by the usual photolithography technique and etching, and the remaining silicon oxide film 1 is removed.
2, a diffusion prevention mask 14 is formed. Thereafter, a film 1 containing impurities of high concentration boron silicate glass (BSG) containing, for example, 4.5% by weight of boron is formed on at least the surface of the diffusion region 13 by a normal chemical vapor deposition method.
5 is formed. The film 15 containing this impurity may be made of, for example, phosphorus silicate glass (PSG) or boron phosphorus silicate glass (BPS) in addition to the boron silicate glass.
It is also possible to use silicon oxide containing impurities such as boron and phosphorus such as G). The silicon-based substrate 11
Is made of, for example, single-crystal silicon or polycrystal silicon, or those containing impurities.

Next, as shown in FIG. 1B, a second step is performed. In this step, at least the region to be diffused 13 is subjected to a thermal oxidation treatment in a nitrogen atmosphere containing oxygen.
A thin oxide film 16 is formed on the surface layer of. At this time, it is also possible to form a thin oxide film 17 on the back surface of the silicon-based substrate 11. Each of the thin oxide films 16 and 17 is formed to a thickness of, for example, 1 nm to 10 nm.

Subsequently, as shown in FIG. 1C, the film 1 containing impurities is subjected to a thermal diffusion process in a nitrogen atmosphere.
5 is diffused into the diffusion region 13 through the thin oxide film 16 to form an impurity diffusion layer 18.

In the above-described impurity diffusion method, a thin oxide film 16 is formed on the surface of the diffusion region 13 before performing the thermal diffusion process, so that the diffusion region 13 and the impurity-containing film 1 are formed.
For example, boron does not precipitate at the interface with the substrate 5. As a result, the hydrophobicity of the surface of the diffusion region 13 is maintained. Further, since the thin oxide film 17 is formed on the back surface of the silicon-based substrate 11, no silicon nitride film is formed on the back surface of the silicon-based substrate 11 during the thermal diffusion process.

Then, as shown in FIG. 1D, the film 15 containing impurities (portion indicated by a two-dot chain line) and the diffusion preventing film 14 (portion indicated by a one-dot chain line) are etched, for example.
And the thin oxide films 16 and 17 (portions indicated by broken lines) are removed.

Next, the heat treatment sequence control in the above impurity diffusion method will be described with reference to FIG. In the figure, the vertical axis indicates the processing temperature, and the horizontal axis indicates the processing time. First, as shown in the figure, in the thermal oxidation process 21, when a silicon-based substrate (not shown) is inserted into a diffusion device (not shown), for example, in a nitrogen atmosphere containing oxygen under the following conditions: The thin oxide films (16) and (17) described in 1 are formed. This condition is such that, for example, an oxidizing atmosphere is applied at a flow rate of 0.50 dm ³ /
And a flow rate of 6.0 dm ³ / min., And the temperature of the atmosphere is set to 900 ° C. The oxidation time is a time required for forming a thin oxide film (16) to a thickness of 1 nm to 10 nm.

The temperature of the thermal oxidation treatment 21 is, for example, 90
The temperature may be 0 ° C. or lower and a temperature at which thin oxide films (16) and (17) are formed. If the heat treatment is performed at a temperature exceeding 900 ° C., the diffusion of the impurity proceeds from the film containing the impurity (15), and at this time, the impurity (for example, between the region to be diffused 13 and the film containing the impurity (15)) Deposition of boron) occurs.

Next, after the thin oxide films (16) and (17) are formed to a predetermined thickness, the atmosphere is changed to a nitrogen atmosphere, and after a temperature rise period 22, a thermal diffusion process 23 is performed. In the thermal diffusion process 23, for example, the flow rate of nitrogen is set to 6.0 dm ³ /
Set to minutes. The temperature of the atmosphere is set to, for example, 1200 ° C. Then, the thermal diffusion process 23 is performed until the impurity diffusion layer (18) reaches a predetermined depth. Thereafter, after the impurity diffusion layer (18) reaches a predetermined depth, the process proceeds to the cooling period 24, and the thermal diffusion process 23 is completed. In the cooling period 24, the temperature is reduced to, for example, 900 ° C.

The temperature of the thermal diffusion process 23 is, for example, 10
What is necessary is just to perform at arbitrary temperature of the temperature range of 50 to 1250 degreeC. For example, when performed at a temperature lower than 1050 ° C., diffusion hardly occurs. At a temperature exceeding 1250 ° C., there arises a problem that the silicon-based substrate (11) is softened and deformed.

Next, the thickness of the thin oxide film (16) will be described with reference to FIG. 3 showing the relationship between the surface resistivity of the impurity diffusion layer and the thickness of the thin oxide film. In the figure, the vertical axis shows the surface resistivity ρs of the impurity diffusion layer, and the horizontal axis shows the thickness t of the thin oxide film.

As shown in the figure, when the thickness of the thin oxide film (16) exceeds 10 nm, the value of the surface resistivity ρs of the impurity diffusion layer (18) suddenly increases. The reason is that in the thermal diffusion process, the impurity is not sufficiently diffused into the diffusion region (13) because the thin oxide film (16) acts as a diffusion mask.

If the thickness of the thin oxide film (17) is less than 1 nm, a silicon nitride film is formed on the back surface of the silicon-based substrate (11) during the thermal diffusion process 22. Therefore, when the thin oxide films (16) and (17) are simultaneously formed, the thin oxide films (16) and (17)
(17) must be formed to a thickness of 1 nm to 10 nm.

Such thin oxide films (16) and (17)
Is formed to a thickness of 1 nm to 10 nm, so that the impurity diffuses from the film (15) containing the impurity into the diffusion region (13) without being hindered by the thin oxide film (16) during the thermal diffusion process 22. At the same time, no silicon nitride film is formed on the back surface of the silicon-based substrate (11).

Next, a second embodiment will be described with reference to the diffusion step diagram of FIG. In the figure, the same components as those described in the first embodiment are denoted by the same reference numerals. As shown in FIG. 4A, a diffusion preventing mask 14 is formed on the surface of the silicon-based substrate 11 except for the surface of the diffusion region 13 of the silicon-based substrate 11 in the same manner as described in the first embodiment.
To form Thereafter, a thin oxide film 16 is formed on at least the surface of the diffusion region 13 by, for example, thermal oxidation. At this time, also on the back surface of the silicon-based substrate 11,
A thin oxide film 17 is formed. Each of the thin oxide films 16 and 1
7 is formed to a thickness of 1 nm or more and 10 nm or less.

Next, as shown in FIG. 4 (2), in the same manner as described in the first embodiment, the surface of the diffusion prevention mask 14 including the surface of the thin oxide film 16 is covered with the film 15 containing impurities.
Is formed.

Thereafter, as shown in FIG. 4C, in the same manner as described in the first embodiment, by the thermal diffusion process,
Impurities (not shown) in the impurity-containing film 15 are diffused into the diffusion region 13 through the thin oxide film 16 to form the impurity diffusion layers 18.

Next, the sequence control of the thermal diffusion process in the second embodiment will be described with reference to FIG. In the figure,
The vertical axis indicates the processing temperature, and the horizontal axis indicates the processing time. First, as shown in the figure, in a loading period 31 in which the silicon-based substrate (11) is inserted into a diffusion device (not shown), for example, a nitrogen atmosphere having a flow rate of 6.0 dm ³ / min is used, and the temperature of the atmosphere is 900 ° C. Set to.

After the loading is completed, the temperature of the atmosphere is set to, for example, 1200 ° C. after a temperature rise period 32. The thermal diffusion process 33 is performed in this state. After the impurity diffusion layer (18) reaches a predetermined depth, the cooling period 3
Then, the process goes to 4 to end the thermal diffusion process 33. In the cooling period 34, the temperature is reduced to, for example, 900 ° C. The temperature of the heat diffusion process 33 may be any temperature in the range of 1050 ° C. or more and 1250 ° C. or less, as described in the first embodiment.

[0030]

As described above, according to the present invention,
Before performing the thermal diffusion treatment, apply a diffusion prevention
By forming the oxide film thinner than the mask, impurities do not deposit at the interface between the diffusion region and the film containing the impurities. As a result, since the hydrophobicity of the surface of the diffusion target region is maintained, dust is less likely to adhere to the silicon-based substrate when a cleaning process is performed thereafter. Therefore, the cleanliness of the silicon-based substrate can be maintained. Further, since a thin oxide film is formed on the back surface of the silicon-based substrate, no silicon nitride film is formed on the back surface of the silicon-based substrate during the thermal diffusion process. Therefore, in a later step, contamination due to detachment of the silicon nitride film can be prevented. Further, since the out-diffusion of impurities can be prevented, the electrical characteristics of the silicon-based substrate can be improved.

[Brief description of the drawings]

FIG. 1 is a diffusion process diagram of a first embodiment.

FIG. 2 is an explanatory diagram of a heat treatment sequence control of the first embodiment.

FIG. 3 is a diagram showing the relationship between the surface resistivity of an impurity diffusion layer and the thickness of a thin oxide film.

FIG. 4 is a diffusion process diagram of the second embodiment.

FIG. 5 is an explanatory diagram of a sequence control of a heat diffusion process in the second embodiment.

FIG. 6 is a diffusion process diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Silicon-based substrate 13 Diffusion area 14 Diffusion prevention mask 15 Film containing impurities 16 Thin oxide film 17 Thin oxide film 18 Impurity diffusion layer 21 Thermal oxidation process 23 Thermal diffusion process 33 Thermal diffusion process

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Politics Fujita 5-1, Noguchikita, Kokubu-shi, Kagoshima Sonny Kokubu Co., Ltd. (56) References JP-A-62-160718 (JP, A) JP-A-49 -27169 (JP, A) JP 48-31378 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/225

Claims (6)

(57) [Claims] 1. A first method comprising: forming a diffusion prevention mask on a surface of a silicon-based substrate except for a surface of a diffusion region of the silicon-based substrate; and forming a film containing an impurity on at least a surface of the diffusion-target region. And a diffusion prevention mask on at least a surface layer of the diffusion target region.
A second step of forming an oxide film having a smaller thickness, and an impurity in the film containing the impurity is diffused into the diffusion region through the thin oxide film by a thermal diffusion process to form an impurity diffusion layer. after the third step, the third step, the wet process the silicon substrate
A semiconductor device according to the fourth means performs the step of
Manufacturing method. 2. A method according to claim 1, wherein, after performing the first step, in the second step, the said in the surface layer and the back surface of the silicon substrate of the diffusion region Expansion
Thickness from diffusing prevention mask to form a thin oxide film, a semiconductor instrumentation to thereafter characterized in that said third step
Method of manufacturing location. 3. A method for removing a surface of a diffusion region of a silicon-based substrate.
Forming a diffusion prevention mask on the surface of the silicon-based substrate.
After that, at least the surface of the diffusion region contains impurities.
The first step of forming a film and the thermal oxidation treatment are performed in an inert gas atmosphere containing oxygen and at an oxidizable temperature of 900 ° C. or less, so that at least the diffusion region Second step of forming a thin oxide film on the surface layer
And performing a thermal diffusion treatment in an inert gas atmosphere and at an arbitrary temperature in a temperature range of 1050 ° C. or more and 1250 ° C. or less to pass impurities in the film containing the impurities through the thin oxide film.
The diffused into the diffusion region, the second to form the impurity diffusion layer
3. A method for manufacturing a semiconductor device , comprising the steps of: 4. After the formation of the diffusion preventing mask on a surface of the silicon substrate except the surface of the diffusion region of the silicon substrate, the diffusion barrier on the surface of at least said the spread region
A first step of forming an oxide film having a thickness smaller than that of the mask, a second step of forming a film containing an impurity on at least a surface of the thin oxide film, diffusing the impurities in the diffusion target region through the thin oxide film, a third step of forming an impurity diffusion layer, after the third step, the wet process the silicon substrate
A semiconductor device according to the fourth means performs the step of
Manufacturing method. 5. The method of manufacturing a semiconductor device according to claim 4, wherein, in the first step, after forming a diffusion prevention mask on a surface of the silicon-based substrate except for a surface of a diffusion region of the silicon-based substrate, An oxide film having a thickness smaller than that of the diffusion prevention mask is formed on a surface layer of the diffusion target region and a back surface of the silicon-based substrate, and thereafter, the second step and the third step are performed. A method for manufacturing a semiconductor device . 6. One of claims 1 to 5
The method of manufacturing a semiconductor device according to claim A method of manufacturing a semiconductor device characterized by the formation of the thin oxide film is ~10nm thickness of less than 1 nm.