JPH06128036A - Silicon carbide part for semiconductor - Google Patents

Abstract

PURPOSE:To enable the stable removal of impurities from the surface of a silicon carbide part and the cleaning of the surface at a high level by mechanically grinding the surface of a silicon carbide part under specific condition. CONSTITUTION:A silicon carbide part for semiconductor, e.g. a vertical boat made of silicon carbide, is produced by mechanically grinding >=75% of the total surface area of the part to a surface roughness Rmax of <=3.2S. Preferably, the part opposite to a wafer is entirely processed. The part subjected to the mechanical grinding is stably cleanable by dry or wet cleaning process in a short time at a high level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide material for semiconductors, which is used for a semiconductor diffusion furnace which is subjected to a heat treatment in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Conventionally, quartz and silicon carbide have been used as members for semiconductor diffusion furnaces. Of these, silica is often used because it is excellent in purity, and impurities on the surface are easily removed by cleaning, resulting in a high level of surface cleanliness. Has the drawback of being short.

For this reason, recently, a diffusion furnace (oxidation furnace) that performs heat treatment in a semiconductor manufacturing process has excellent heat resistance characteristics, so that a soaking tube (liner tube), a reaction tube (process tube), a jig ( Silicon carbide members are often used in wafer boats, plates, supports, etc.).

In this case, when these members are used, in order to remove impurities on the surface and improve cleanliness, they are regularly cleaned before and during the period of use. In particular, since the Si wafer mounted on the boat is loaded into the process tube and heat-treated, the process tube and the jig are required to have the purity of the substrate and the cleanliness of the surface. Therefore, the process tube and jig are thoroughly washed before use.

Wet cleaning is adopted as this cleaning method. Wet cleaning is performed by immersing in a 5-10% hydrofluoric acid solution,
It is common to rinse with pure water. Quartz members can be used after the surface impurities are easily removed by this wet cleaning. However, in the case of silicon carbide materials, this wet cleaning does not sufficiently remove surface impurities. Therefore, dry cleaning with hydrochloric acid gas or the like is required, and dry cleaning with hydrochloric acid gas is generally performed especially at high temperature.

[0006]

However, it takes a long time to remove impurities on the surface of a silicon carbide member by cleaning, and the cleanliness level of the cleaning is limited.
It has a drawback that the cleanliness varies greatly and the characteristics during use are not stable.

Further, the above-mentioned dry cleaning requires a very long time of 3 to 5 days or more to perform necessary cleaning. That is, in dry cleaning, the tube or jig to be used is set in the diffusion furnace and high temperature (1
(200 ° C. or higher), and after reaching this temperature, a few percent hydrochloric acid gas is flowed for 24 to 48 hours or more, and the hydrochloric acid gas is further stopped to remove residual chloride gas, and baking is performed for 24 to 48 hours or more. There is a need.

Moreover, even if the cleaning is performed for such a long time, if the result of the contamination evaluation by the subsequent wafer mounting fails, the cleaning / evaluation test must be performed again, and this process is repeated several times. There are times. Therefore, this long-time dry cleaning process causes a decrease in productivity and an increase in production cost.

The present invention has been made in order to solve the above problems, and can shorten the cleaning time, and can perform stable and high-level cleaning. Therefore, it was used for a semiconductor diffusion furnace. In this case, it is an object of the present invention to provide a silicon carbide material for semiconductors, which can prevent contamination of a Si wafer as much as possible.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, the surface of the silicon carbide member has a maximum surface roughness of 75% or more of the total surface area ( (Rmax) 3.2S or less, the mechanical grinding process not only significantly shortens the cleaning time in cleaning the impurities on the surface of the member, but also causes variations in cleanliness compared with conventional members. It has been found that a high level of cleaning can be performed stably without the above.

That is, in general, a silicon carbide member is a sintered body member in which a primary sintered body of a green compact is joined to form an approximate shape and then sintered and then sandblasted or surface-blasted. After assembling and joining, it is manufactured by performing the final sandblasting process again. However, the present inventor cannot remove the irregularities and pores on the surface of the member because the surface finishing of the conventional silicon carbide member is performed by sandblasting.
Further, since the surface roughness becomes rougher than 10 S, the total surface area becomes large, and the amount of impurities on the surface of the member depends on the total surface area. Therefore, the larger the surface area, the larger the total amount of impurities. When unevenness and pores are present in the surface, the cleaning efficiency is reduced, impurities are likely to remain, and it is found that the characteristics at the time of use are reduced, and as described above, the surface area is reduced by mechanical grinding of the member, that is, By reducing the surface roughness and removing surface irregularities and pores, not only can the cleaning time be significantly shortened, but more stable and higher level cleaning can be achieved compared to conventional products. They have found the present invention and made the present invention.

Therefore, the present invention provides a silicon carbide-based member for semiconductor, in which 75% or more of the total surface area is machine-ground to have Rmax = 3.2S or less.

The present invention will be described in more detail below. The silicon carbide material for semiconductors according to the present invention is, in particular, a soaking tube (liner tube), a reaction tube (process tube), a jig (wafer boat, plate, support base, etc.). ) Etc., and 75% or more, more preferably 85% or more of the total surface area thereof is finished to have Rmax = 3.2S or less, more preferably 1.5S or less. R
If max is coarser than 3.2S, impurities cannot be removed sufficiently during the cleaning, and the object of the present invention cannot be achieved.

Further, although it is preferable to process the entire surface of the member, it is difficult to process it depending on the shape, so processing the entire surface causes a rise in manufacturing cost. However, in that case as well, at least 75% of the total surface area needs to be processed, and at that time, it is preferable to completely process the portion facing the wafer.

The selection of the above-mentioned mechanical grinding method and the type of grindstone used for it is not particularly limited, but the grain size of the grindstone is preferably # 60 to # 240, particularly # 120 to # 240. If it is coarser than # 60, the strength of the product may be lowered, while if it is finer than # 240, the processing speed may be slowed down, which may increase the processing cost. A diamond grindstone is preferably used as the grindstone, but a commonly used grindstone such as a borazon grindstone or a GC grindstone may be used.

After the silicon carbide member is sintered, its surface is usually finished by sandblasting. According to the present invention, the surface of the sintered body thus sandblasted can be mechanically ground. However, for complex shapes such as a vertical boat, the sintered body parts are sandblasted if necessary, and then ground and joined. As a result, the processing becomes easy and the manufacturing cost can be reduced.

When cleaning the member of the present invention that has been mechanically ground as described above, wet and dry cleaning are performed. Wet cleaning is performed after immersing in a 5-10% hydrofluoric acid solution.
A method of sufficiently rinsing with pure water can be generally adopted. On the other hand, in the dry cleaning, the member is set in a diffusion furnace, heated to a high temperature of 1200 ° C. or higher while flowing dry oxygen gas, and after reaching this temperature, a few percent of hydrochloric acid gas is flowed for 24 to 48 hours or more to remove residual chlorine. In order to remove the product gas, a method of further stopping the hydrochloric acid gas and performing the baking for 24 to 48 hours or more is preferable.

[0018]

EFFECTS OF THE INVENTION The silicon carbide-based member of the present invention enables cleaning of the surface of the member for removing impurities at a high level in a short time and stably.

[0019]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example A silicon carbide vertical boat shown in FIG. 1 (material: SEN-8000 manufactured by Shin-Etsu Chemical Co., Ltd.)
Was produced. At that time, a member subjected to grinding processing was assembled using a diamond wheel having a grain size of # 180 and sintered. The surface roughness of the processed portion is 2.4S. At that time, the surfaces A and B were left as blasted, and the surface roughness of the blasted surface was 12S. The total surface area of this boat was 1480 cm ² , and the surface to be ground was 1150 cm ² , which was 78% of the total surface area.

Next, the boat was immersed in a 7% hydrofluoric acid solution at 60%.
After soaking for a minute, it was taken out and thoroughly rinsed with pure water. Then, after drying for 24 hours on a clean bench, the boat was inserted into the reaction tube of the diffusion furnace, and 3 liter / min. Flowing oxygen gas at 6 ° C / min. The temperature was raised to 1250 ° C. 3 liters / mi after reaching 1250 ° C
n. Oxygen gas and 0.15 l / min. Hydrochloric acid gas of was flowed in the tube for 48 hours. Then, the hydrochloric acid gas was stopped, and only oxygen gas was flowed for 48 hours to complete the cleaning.

[Comparative Example] A vertical boat having the same specifications as those of the example was manufactured and washed in the same manner as the example except that the surface thereof was only blasted (the surface roughness in this case was 12S). went.

Si wafers (CZ) were placed on the cleaned process tubes and wafer boats in the examples and comparative examples.
-P type, <111>) loaded, 1150 ° C x 3 in oxygen
0 min. It heat-processed on condition of. The lifetime of the wafer was measured in order to examine the degree of contamination on the Si wafer at this time. The results are shown in Table 1. Note that the lifetime of the wafer becomes longer as the contamination is less.

[0024]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic plan view of a vertical boat used to evaluate the degree of contamination on Si wafers in Examples and Comparative Examples of the present invention.

Claims (1)

[Claims] 1. 75% or more of the total surface area has Rmax = 3.
A silicon carbide-based member for semiconductor, which is mechanically ground to 2S or less.