JP3365098B2 - Manufacturing method of epitaxial semiconductor wafer - 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 for producing a high quality epitaxial semiconductor wafer which enables a high yield in a device process, and has an extremely thin thermal oxidation on both sides of the wafer before vapor phase growth of a silicon thin film. By performing a specific oxide film treatment such as a film and then inserting and arranging it in the reactor to perform epitaxial growth, the process before the epitaxial reaction can be simplified, and uneven etching on the back surface of the wafer can be significantly reduced to form a high-quality epitaxial thin film. The present invention relates to a method of manufacturing an epitaxial semiconductor wafer capable of forming a film.

[0002]

2. Description of the Related Art A process for growing an epitaxial thin film on a semiconductor silicon wafer usually consists of the following processes. Explaining based on the heat pattern diagram shown in FIG. 3, first, A is heated to a predetermined temperature range in a gas atmosphere containing hydrogen gas, and then B is etched for several minutes with a gas containing hydrogen chloride, etc. After removal of contamination and activation of the wafer surface, C atmosphere purge, epitaxial growth on the wafer surface using D silane-based gas, E atmosphere purge, and F cooling at a predetermined cooling rate.

However, a wafer used for epitaxial growth is usually finished by RCA cleaning, and a natural oxide film of about 10 Å is grown on the wafer surface by a chemical solution, but under a hydrogen atmosphere during the epitaxial growth process. In this case, the natural oxide film is immediately etched by the reducing action of hydrogen gas, and the surface of the silicon wafer is exposed.In particular, the hydrogen chloride gas that is subsequently introduced wraps around the back surface of the wafer, so It was locally etched.

The above-mentioned epitaxial wafer having uneven etching on the back surface of the wafer causes a decrease in adhesive force when a metal contact is made from the back surface of the wafer like a disk read device, resulting in peeling of metal during dicing and a reduction in yield. There was a problem that caused it.

[0005]

On the other hand, as a method for reducing the above problems in the epitaxial thin film growth process, a thermal oxide film is previously formed on the entire surface of the wafer or CVD (Chemi) is used.
Cal Vapor Deposition) There is a method in which an oxide film or a nitride film is grown to a thickness of about 1000 Å or more, then only the wafer surface is etched, and then an epitaxial thin film is grown.

However, when the above steps are carried out, as a pretreatment up to the epitaxial step, oxide film heat treatment or CVD treatment, wafer backside masking,
A series of processing steps from wafer surface film etching, wafer backside masking removal, and RCA cleaning are required. Further, after the epitaxial film growth, a process of removing the wafer backside growth film by the above method is required as a post-process, and there is a problem that a complicated process is required.

The present invention simplifies the conventional wafer processing steps before and after the growth of a silicon epitaxial thin film, and enables the production of high-quality epitaxial thin films with a high yield in the device step without uneven etching on the back surface of the wafer. The purpose of the present invention is to provide an epitaxial thin film manufacturing method.

[0008]

SUMMARY OF THE INVENTION The inventors of the present invention have aimed to provide a method for manufacturing a high-quality epitaxial semiconductor wafer that does not cause uneven etching on the back surface of a wafer in a device process and that enables a high yield, and a silicon epitaxial thin film. As a result of various studies on the wafer processing steps before and after the growth, before the vapor phase growth of the silicon thin film, a specific film forming process such as an extremely thin thermal oxide film or a CVD film was performed on both sides of the wafer, and then the wafer was inserted and placed in the reactor. By epitaxial growth, the ultra-thin oxide film on the wafer surface can be easily removed during etching in hydrogen atmosphere or hydrogen chloride gas, while the back surface of the susceptor has a slower etching rate than the front surface. Since the thin oxide film acts as a mask and protects it, it is possible to significantly reduce the unevenness of the wafer backside etching. , As well as knowledge that can be greatly simplified as compared with the epitaxial reaction previous step to the conventional method described above and have completed the present invention.

That is, the present invention provides a method for manufacturing an epitaxial semiconductor wafer in which a silicon thin film is vapor-deposited on the surface of a semiconductor wafer, and the front and back surfaces of the wafer are subjected to gas etching or hydrogen atmosphere in an epitaxial reaction process in an apparatus. After forming an oxide film or nitride film by ultra-thin thermal oxidation or dry plating having a thickness that can be removed by etching, the epitaxial reaction process is performed by inserting the oxide film or nitride film into the epitaxial reactor without removing the oxide film. And a method for manufacturing an epitaxial semiconductor wafer.

Further, according to the present invention, in the above structure,
When the oxide film is a thermal oxide film, the film thickness is 10Å to 20
A method for manufacturing an epitaxial semiconductor wafer having a thickness of 10Å and a method for manufacturing an epitaxial semiconductor wafer having a film thickness of an oxide film or a nitride film by dry plating of 10Å to 100Å are also proposed.

In the present invention, the thermal oxidation treatment for forming the oxide film is not particularly limited as long as the desired oxide film thickness can be obtained. In the present invention, the dry plating can be adopted by any vapor deposition method such as vacuum deposition, sputtering, CVD, ion plating, and plasma plating, and a nitride film as well as an oxide film has the same effect.

[0012]

The function and effect of the oxide film in the present invention will be described in detail with reference to the drawings. FIG. 1 is a vertical cross-sectional explanatory view of a wafer showing a process in which minute defects are incorporated during epitaxial growth when a silicon oxide film is provided with a thermal oxide film. FIG. 2 is a longitudinal sectional view showing a silicon wafer during etching. In the present invention, the extremely thin oxide film or nitride film is formed on the front and back surfaces of the wafer in the epitaxial process, as shown in FIG. 2, on the front and back surfaces of the wafer 1 placed in the storage hole 11 of the susceptor 10. This utilizes the difference in the etching rate of the oxide film due to the difference in the hydrogen gas flow rate. That is, since the hydrogen gas flow 12 (main flow) on the front surface side of the wafer 1 is fast, the etching rate of the oxide film is also high, while the gas flow 13 on the back surface side of the wafer 1 is due to the entrainment of hydrogen gas and thus the etching of the oxide film. It takes advantage of the very slow speed.

Therefore, for example, in the oxide film formed by the heat treatment, the oxide film is completely removed only on the wafer surface side during the epitaxial process, and then the silicon wafer surface is etched by introducing hydrogen chloride gas, and then the silicon-based gas is used. Epitaxial thin film growth is performed.
On the other hand, on the back side of the wafer, hydrogen chloride gas is introduced in the presence of the oxide film, so even if the hydrogen chloride gas enters the back side of the wafer, the oxide film acts as a mask. Is not etched. That is, the present invention makes it possible to more easily manufacture a silicon epitaxial thin film having no wafer backside etching unevenness as compared with the conventional method.

Further, as shown in A of FIG. 1, the microscopic defects 2 scattered in the silicon wafer 1 are taken into the thermal oxide film 3 after the heat treatment as shown in B, so that the point becomes a weak spot, As shown in C, it is first etched during hydrogen reduction, and eventually pits 4 are locally generated on the silicon wafer 1,
These pits 4 will be reflected in the grown epitaxial film 5. Therefore, in the present invention, the oxide film thickness in the case of the thermal oxide film treatment is required to be at least 10 Å or more as the above-mentioned back side mask, but in order to reduce the above epitaxial defects as much as possible, it is preferably 20 Å or less. is there. On the other hand, in the case of a CVD oxide film, since the oxide film is deposited on the surface of the silicon wafer, it is not necessary to consider the above, and the film thickness is at least 1 in the same manner.
0 Å or more is necessary, but considering the etching time of hydrogen gas for the CVD oxide film on the wafer surface, thick C
Since the VD oxide film takes time to be completely reduced and removed, which causes a decrease in productivity, the thickness is set to 100 Å or less.

[0015]

【Example】

Example 1 A single crystal silicon wafer obtained by the CZ method was used for mirror finishing, and a thermal oxide film was formed on the wafer surface in a heat treatment furnace under the conditions of oxygen, nitrogen, temperature of 800 ° C., and holding time of 2 minutes. When the oxide film thickness was measured with an ellipsometer, the film thickness was 15Å. afterwards,
The wafer was placed in an epitaxial growth furnace, heat treatment was performed in a hydrogen atmosphere in the process as shown in FIG. 3, and the oxide film thickness was measured again by an ellipsometer. The oxide film etching rates on the front and back surfaces of the wafer were determined from the changes in the oxide film thickness before and after hydrogen annealing of the wafer. The etching rate on the front side of the wafer was 8 to 10 Å / min, and on the back side was 0.7 Å / min. After hydrogen annealing, perform the epitaxial process with the heat pattern shown in FIG.
An epitaxial film having a film thickness of 5 μm was formed, but back surface etching unevenness on the wafer did not occur.

Example 2 A single crystal silicon wafer obtained by the CZ method was used to perform mirror finishing, and a target 20 was obtained in a CVD furnace.
Å, atmosphere A CVD oxide film was formed on the wafer surface under the conditions of helium gas base, monosilane, oxygen gas, temperature, 400 ° C, and holding time of 15 seconds, and the oxide film thickness was measured with an ellipsometer. The film thickness was 25Å. there were. After that, the wafer is put into an epitaxial growth furnace, heat treatment is performed in a hydrogen atmosphere in the process as shown in FIG. 3, the oxide film thickness is measured again by an ellipsometer, and the oxide film thickness before and after hydrogen annealing of the wafer is measured. From the change, the etching rate of the oxide film on the front and back surfaces of the wafer was obtained. The etching rate on the front side of the wafer was 7 to 10 Å / min, and on the back side was 0.8 Å / min. After hydrogen annealing, an epitaxial process was performed with the heat pattern shown in FIG. 3 to form an epitaxial film having a film thickness of 5 μm, but back surface uneven etching on the wafer did not occur.

Comparative Example 1 Next, the same test as in Examples 1 and 2 was performed on a wafer in which an oxide film formed by cleaning with ammonia / hydrogen peroxide solution / water had a film thickness of about 40 Å. ,
It was found that the wafer surface etching rate is 25 to 30 Å / min, the back surface side etching rate is 14 Å / min, and the etching rate is higher than that of the thermal oxide film, so that it cannot be used in the epitaxial process of the present manufacturing method.

Example 3 About 10Å, 20Å, 3 by the thermal oxidation furnace in Example 1
Four kinds of silicon wafers on which oxide films having a thickness of 0Å and 50Å were formed and a wafer after normal RCA cleaning were put into an epitaxial growth apparatus, and the above process was performed to visually inspect the wafer after the epitaxial thin film growth. The wafer after RCA cleaning had uneven etching on the back surface, but the wafer having an extremely thin thermal oxide film did not have uneven etching on the back surface. But,
Oblique light inspection showed that the haze level of the epitaxial film surface was deteriorated and the defect density was increased as the thickness of the wafer was increased. Since the sample has a thermal oxide film thickness of 20Å and can be used as a product, the thermal oxide film thickness needs to be 20Å or less.

Example 4 Next, using the CVD furnace in Example 2, the target film thickness was in the range of about 10Å to 100Å, atmosphere helium gas base, monosilane, oxygen gas, temperature, 400 ° C.,
Under the condition of holding time of several tens of seconds to several minutes, a silicon oxide film having a CVD oxide film grown to a thickness of about 10Å, 30Å, 50Å, 75Å, 100Å and a thickness was subjected to the same test as in Example 3 There was no unevenness and no deterioration of the haze level on the surface of the epitaxial film was observed. Also, the etching rate of the oxide film is about 10Å
/ Min, it takes about 10 minutes to remove the 100 Å CVD oxide film by etching, and if the thickness is made thicker than this, the productivity is lowered.

[0020]

According to the present invention, a silicon wafer is subjected to a specific film-forming treatment such as an extremely thin thermal oxide film or a CVD film on both sides of the wafer before the epitaxial growth of a silicon thin film, and then inserted into a reactor for epitaxial growth. As a result, the ultra-thin oxide film on the wafer surface is easily removed during hydrogen atmosphere or hydrogen chloride gas etching.On the other hand, the back surface side mounted on the susceptor has a slower etching rate than the front surface side. There for protection acts as a mask, it is possible to reduce the etching unevenness due included around the wafer back surface due to hydrogen chloride gas in the epitaxial thin film growth process can be improved the yield in the device process can provide a high-quality epitaxial thin film.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view of a wafer showing a process in which microscopic defects are incorporated during epitaxial growth when a silicon oxide film is provided with a thermal oxide film.

FIG. 2 is a vertical cross sectional view showing a silicon wafer during etching.

FIG. 3 is a heat pattern diagram in a process of growing an epitaxial thin film.

[Explanation of symbols]

1 wafer 2 Small defects 3 Thermal oxide film 4 pits 5 Epitaxial film 10 susceptor 11 storage holes 12, 13 Gas flow

Claims (3)

(57) [Claims] 1. A method of manufacturing an epitaxial semiconductor wafer in which a silicon thin film is vapor-deposited on the surface of a semiconductor wafer, wherein the front and back surfaces of the wafer are removed by gas etching in an epitaxial reaction step in an apparatus or etching under a hydrogen atmosphere. An epitaxial semiconductor characterized by forming an oxide film or a nitride film by an extremely thin thermal oxidation or dry plating having a thickness to be obtained, and then inserting and arranging the oxide film into an epitaxial reaction apparatus without removing the oxide film to perform an epitaxial reaction step. Wafer manufacturing method. 2. The method for producing an epitaxial semiconductor wafer according to claim 1, wherein the film thickness is 10Å to 20Å when the oxide film is a thermal oxide film. 3. The method for manufacturing an epitaxial semiconductor wafer according to claim 1, wherein the oxide or nitride film formed by dry plating has a film thickness of 10Å to 100Å.