JP2003197549A - Method of manufacturing epitaxial wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which an epitaxial wafer that has a highly flat surface and high cleanliness and is low in particle level can be manufactured. <P>SOLUTION: After etching the surface of a silicon wafer, the etched surface of the wafer is cleaned with an SC-1 cleaning fluid. Then the cleaned wafer is dipped in an HF solution. After taking out the wafer from the HF solution, epitaxial growth is performed on the surface of the wafer by adjusting the duration of leaving the wafer in the atmosphere for eight hours or shorter. The epitaxial growth can be performed at a high temperature of ≥1,000°C or a low temperature of 400°C to ≤1,000°C or the epitaxial growth can be repeated alternately at the high temperature and low temperature. When the epitaxial growth is performed at the low temperature, the cost of the epitaxial growth can be reduced due to the low temperature. In addition, the epitaxially grown surface can be polished. <P>COPYRIGHT: (C)2003,JPO

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 an epitaxial wafer having improved surface quality.

[0002]

2. Description of the Related Art Conventional epitaxial wafers (E
W) is usually manufactured at a high temperature of 1000 ° C. or higher after completion of the polished wafer (PW) manufacturing process.
It was common to perform epitaxial growth on the W surface. That is, it was epitaxially grown on the wafer surface after polishing.

[0003]

However, the above-mentioned E
In the production of W, abnormal projections are likely to occur on the epitaxially grown surface, and the particle level thereof is inferior.
Further, there is a problem in surface quality that the degree of contamination is high. Therefore, it is possible to solve the above problems by further polishing the wafer surface epitaxially grown in this way. However, even with this method, there is a problem that the polishing process is increased.

Therefore, as a result of intensive studies to solve the above problems, the inventors of the present invention have eliminated the polishing step before epitaxial growth, performed a predetermined clean cleaning after etching, and further, on the wafer surface. By completing the epitaxial growth, we established a manufacturing process that can solve the problem. For that purpose, after cleaning with a mixed solution of alkali / hydrogen peroxide solution (for example, SC-1 cleaning solution) before epitaxial growth, a treatment with HF (hydrofluoric acid) is performed to simultaneously remove organic substances and metal impurities on the wafer surface. It is important to. Also,
If left in the atmosphere for a long time after these treatments, the surface state changes due to the oxidizing effect of organic substances or oxygen in the atmosphere, making epitaxial growth impossible. Therefore, the limit for this storage time (leaving time) is 8
It should be about time. However, this is the case in an oxidizing atmosphere (including the atmosphere).

[0005]

According to a first aspect of the present invention, the surface of a silicon wafer after etching is washed with a mixed solution of alkali / hydrogen peroxide water, and then washed with hydrofluoric acid. This is a method of manufacturing an epitaxial wafer in which the silicon wafer is epitaxially grown on the surface of the silicon wafer by controlling the storage time in the atmosphere within 8 hours.

The invention described in claim 2 is the method for manufacturing an epitaxial wafer according to claim 1, wherein a part of the epitaxial surface of the silicon wafer is removed after the epitaxial growth. For example, polishing is performed.

The invention described in claim 3 is the method for manufacturing an epitaxial wafer according to claim 1 or 2, wherein the epitaxial growth is performed at a high temperature of 1000 ° C. or higher.

The invention described in claim 4 is the method for producing an epitaxial wafer according to claim 1 or 2, wherein the epitaxial growth is performed at a low temperature of 400 ° C or higher and lower than 1000 ° C.

[0009]

According to the method of the present invention, the silicon wafer after the etching treatment is first cleaned with a mixed solution of alkali / hydrogen peroxide water (for example, SC-1 cleaning solution). next,
The wafer surface is treated with HF (hydrofluoric acid). For example, the wafer is immersed in an HF solution. After this, the storage time limit for leaving in the atmosphere is 8
Epitaxial growth is performed on the surface of the wafer for about a time. This epitaxial growth may be performed at a high temperature of 1000 ° C. or higher, or at a low temperature of less than 1000 ° C. and 400 ° C. or higher. Further, so-called multi-step epitaxial growth may be performed in which the high temperature epitaxial growth and the low temperature epitaxial growth are alternately repeated. Low-temperature epitaxial growth makes it possible to achieve cost reduction by lowering the temperature.

After the above-mentioned epitaxial growth, polishing treatment, for example, is performed. As a result, it is possible to remove a part of the wafer surface to suppress the generation of protrusions on the wafer surface, adhesion of dust, and the like, and to omit the conventional polishing process before the epitaxial growth.

[0011]

EXAMPLES Examples of the present invention will be described below. According to the method according to the embodiment of the present invention, the following results could be obtained. As a specific example of the embodiment method, in the oxidation-reduction treatment after etching, a mixed solution of an inorganic alkali and hydrogen peroxide solution having an etching rate for silicon of 10 Å / min or less is used. For example, it is a mixed solution containing KOH (1 wt%) and H ₂ O ₂ (1 vol%) at 50 ° C. The next HF cleaning is
The immersion treatment is performed in a HF solution having a concentration of 1.5%. Then, the silicon wafer was washed with pure water and epitaxially grown on the surface (thickness was about 5 μm). The film forming conditions are such that the growth temperature in the CVD furnace is 660 ° C. or lower,
The film formation rate was adjusted to 200 angstroms / minute or less. Further, for example, a known dead weight type polishing machine was used to perform polishing to 2 μm or less.

FIGS. 1A, 1B and 1C show the surface flatness (indicated by the haze level of the particle counter "Surfscan (trade name)"), the particle level (including protrusions), the surface by this method. The cleanliness is shown together with the comparative example. In the comparative example, epitaxial growth was performed in an epitaxial furnace, and the thickness of the epitaxial film was 3 μm. As can be seen from these figures, according to the manufacturing method of the present invention, an epitaxial wafer having a high quality surface can be obtained.

FIG. 2 shows the relationship between the X-ray diffraction intensity and the storage time in the method of the present invention. That is,
It shows the relationship between the storage time of leaving the silicon wafer after HF cleaning in the atmosphere of a clean room and the crystal state of the epitaxial film surface by the subsequent epitaxial growth. As shown in this graph, when the storage time exceeds 8 hours, the proportion of polycrystalline silicon on the surface increases. From this, it is understood that it is necessary to set the storage time to 8 hours or less and perform the next epitaxial growth.

[0014]

According to the method of the present invention, the surface quality of the epitaxial wafer can be improved. Specifically, the surface flatness can be increased (the haze level can be reduced). Further, it is possible to reduce protrusions and the like on the surface and reduce the particle level. Furthermore, the surface contamination can be reduced. Further, it is possible to achieve cost reduction by lowering the temperature. Note that this also means that the conventional polishing process is omitted.

[Brief description of drawings]

FIG. 1 is a graph showing surface flatness, particle level, and surface cleanliness of an epitaxial layer of an epitaxial wafer manufactured by a manufacturing method according to an example of the present invention together with a comparative example.

FIG. 2 is a graph showing the relationship between the surface quality and the storage time of an epitaxial wafer according to an example of the present invention.

Continued front page    (72) Inventor Kazunari Takaishi             3-8-16 Iwamotocho, Chiyoda-ku, Tokyo 3             Ryo Material Silicon Co., Ltd. (72) Inventor Kotaro Shimizu             3-8-16 Iwamotocho, Chiyoda-ku, Tokyo 3             Ryo Material Silicon Co., Ltd. F-term (reference) 4G077 AA03 BA04 DB01 EA02 ED06                       EE02 FG18 TK01 TK10                 5F045 AB02 AD08 AD09 AD10 AD11                       AD12 AD13 AD14 AD15 AD16                       AD17 AD18 BB02 BB14 HA04

Claims (4)

[Claims] 1. A surface of a silicon wafer after etching is washed with a mixed solution of an alkali / hydrogen peroxide solution, and then hydrofluoric acid is washed, and then the silicon wafer is stored in the atmosphere for a storage time. A method for manufacturing an epitaxial wafer, which is managed within 8 hours and is epitaxially grown on the surface of this silicon wafer. 2. The method for producing an epitaxial wafer according to claim 1, wherein a part of the epitaxial surface of the silicon wafer is removed after the epitaxial growth. 3. The method for producing an epitaxial wafer according to claim 1, wherein the epitaxial growth is performed at a high temperature of 1000 ° C. or higher. 4. The epitaxial growth is carried out at a low temperature of 400 ° C. or higher and lower than 1000 ° C.
A method for manufacturing an epitaxial wafer according to item 1.