JPH0677310A - Washing method for silicon carbide member - Google Patents

Abstract

PURPOSE:To make it possible to wash in a short time and with a high washing degree by performing dry type hydrochloride gas washing for a silicon carbide member for producing semiconductors, then reducing pressure, removing a residual gas in the system, and performing oxygen gas flow washing. CONSTITUTION:Wet washing is performed by immersing a silicon carbide member into a 5 to 10% hydrofluoric acid solution for 60 to 120 minutes. Then, it is taken out from said solution and acid is fully removed by fully rinsing it with pure water, and natural drying is performed. When performing dry type washing for a dried silicon carbide member, the silicon carbide member is set in a diffusion furnace and heating is started. Then, after reaching a predetermined temperature, dry hydrochloride gas washing is performed in which oxygen gas and hydrochloride gas flow. Thereafter, the pressure is reduced in the system, hydrochloride gas is applied, the pressure is reduced again and the residual gas in the system is removed. Then, oxygen gas flow washing is performed and dry washing is completed. By doing this, the washing can be performed in a short time with a high degree of washing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a silicon carbide based material for manufacturing various semiconductors, and more particularly to a silicon carbide capable of performing a dry cleaning following a wet cleaning in a short time with a high cleaning degree. The present invention relates to a method for cleaning quality members.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
In a manufacturing process of semiconductors such as Si wafers, a diffusion furnace (oxidation furnace) for heat-treating semiconductors has a soaking tube (liner tube) because of its excellent heat resistance.
Reaction tube (process tube), jig (wafer boat)
A silicon carbide-based member made of silicon carbide or the like is often used. When a Si wafer is subjected to heat treatment using these members, the Si wafer is placed on a jig and loaded into a process tube for heat treatment. The material is required to have a high degree of purity and the surface of the silicon carbide material to have a high degree of cleaning.

Therefore, silicon carbide members such as process tubes and jigs must be sufficiently cleaned before and during the period of use. In this case, the cleaning method is wet hydrofluoric acid cleaning. After that, the method of setting in a diffusion furnace and dry-cleaning at high temperature using hydrochloric acid gas is generally adopted.

A detailed description will be given of such a cleaning method.
First, 5 to 10% of materials such as process tubes and boats
After being dipped in the hydrofluoric acid solution, the wet cleaning is performed by sufficiently rinsing with pure water. If the tube or jig is made of quartz, it can be used simply by performing such wet cleaning, but in the case of silicon carbide-based members, wet cleaning alone is not sufficient, and the original characteristics of silicon carbide are exhibited. In order to do so, after the above-mentioned wet cleaning, it is necessary to carry out dry baking using a baking furnace or hydrochloric acid gas in the diffusion furnace to remove impurities existing on the surface of the silicon carbide material as chloride gas. is there.

In this dry cleaning, a tube and a jig that have been wet cleaned are set in a diffusion furnace, heated to a high temperature of 1200 ° C. or higher while flowing dry oxygen gas, and then several percent hydrochloric acid gas is supplied for 24 to 48 hours or more. For 24 to 4 hours, and then the hydrochloric acid gas is turned off to remove residual chloride.
This is a cleaning method in which air baking is performed for 8 hours or more, which requires a very long time of 3 to 5 days or more, and in some cases 7 to 8 days or more.

Further, after dry-cleaning, the wafer is mounted on the silicon carbide material and a contamination evaluation test is conducted. If the result is not acceptable, the silicon carbide material must be washed again to carry out an evaluation test. If this process has to be repeated several times until the silicon-based member is ready for use, it takes a long time, and the dry cleaning process causes a decrease in semiconductor productivity and an increase in production cost.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a method for cleaning a silicon carbide based member for semiconductor production, which can perform dry cleaning in a cleaning step of a silicon carbide based member in a short time with a high degree of cleaning.

[0008]

Means and Actions for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has conducted a dry hydrochloric acid gas cleaning on a silicon carbide material for semiconductor production, and then reduced the pressure,
It has been found that cleaning the oxygen gas flow cleaning after removing the residual gas in the system enables cleaning in a short time and with a high cleaning degree.

That is, as a result of various investigations by the inventor of the present invention on dry cleaning of a silicon carbide-based member for semiconductor production, since the surface of the silicon carbide-based member has irregularities and pores, hydrochloric acid gas causes the tip of the recess to be exposed. The chloride gas generated by the reaction of hydrochloric acid gas and impurities with hydrochloric acid gas is liable to remain in the recesses, which requires long-term cleaning and sufficient cleaning. In some cases, dry hydrochloric acid gas cleaning is performed, and then the system is depressurized, and then oxygen gas flow cleaning is performed again to clean the recesses and pores in the surface of the silicon carbide-based member. It was found that not only the residual gas such as chloride gas is easily removed and the cleaning time is significantly shortened, but also a high level of cleaning degree is possible as compared with the conventional method, and the present invention is made. Came to.

The present invention will be described in more detail below. In the method for producing a silicon carbide-based member for semiconductor production of the present invention, the member is cleaned with dry hydrochloric acid gas, depressurized, and residual gas in the system is removed. , Oxygen gas flow cleaning is performed.

Here, the cleaning method of the present invention can be applied to a silicon carbide member manufactured by any method such as a reaction sintering method, a recrystallization method and an atmospheric pressure sintering method. Examples of silicon carbide members include liner tubes, boats, cantilevers, forks and the like.

In order to clean the silicon carbide-based member by the cleaning method of the present invention, first, preferably the silicon carbide-based member is used for 5 to 10 times.
% Hydrofluoric acid solution for 60-120 minutes
Perform wet cleaning. Then, it is taken out of the hydrofluoric acid solution, rinsed with pure water sufficiently to remove the acid, and naturally dried.

When dry-cleaning a dried silicon carbide member, the member is set in a diffusion furnace and heating is started. In this case, both members can be cleaned at the same time by disposing the jig in the tube. The heating is started from room temperature, and the temperature is raised at a heating rate of about 5 to 15 ° C./minute while flowing oxygen at a flow rate of several liters / minute or less, preferably 1 to 5 liters / minute. In this case, about 20 during heating
1 at each temperature of 0,400,600,800,1000 ℃
It is preferable to hold for up to 4 hours. The ultimate temperature for heating is 1
Although the temperature may be 000 to 1200 ° C., the higher the temperature is, the greater the cleaning effect is. Therefore, it is preferable to set the temperature to 1200 ° C. or higher. More preferably, it is set to 1280 ° C.

Next, after reaching a predetermined temperature, dry gas cleaning is performed. This dry hydrochloric acid gas cleaning can be performed by flowing oxygen gas and hydrochloric acid gas. afterwards,
It is preferable to reduce the pressure in the system using a vacuum pump or the like. As the degree of pressure reduction, the lower the pressure, the greater the effect of removing the residual gas. Therefore, the pressure is preferably set to 500 Torr or less, particularly 100 Torr or less.

After reaching a predetermined degree of vacuum, the vacuum pump is stopped and oxygen gas and hydrochloric acid gas are caused to flow. In this case, the flow rate of oxygen can be the same as above, and the amount of hydrochloric acid gas The flow rate is 0.1 to 3 liters / minute, especially 0.15 to 0.
It is preferably 3 liters / minute. The time for flowing the oxygen gas and the hydrochloric acid gas is preferably several hours or less, and particularly preferably 2 to 4 hours. In addition, it is desirable that the steps from the pressure reduction to the cleaning with hydrochloric acid gas as described above are performed once or more, preferably 2-3 times.

After the cleaning with hydrochloric acid gas is completed, the same depressurization as above is carried out again to remove the residual gas in the system, and then the oxygen gas flow is carried out preferably at the same flow rate as above for several hours. Wash and finish dry washing.

By cleaning the silicon carbide member by the above-mentioned method, the cleaning process which has conventionally required 7 to 8 days can be shortened to about 3 days, and a high level cleaning can be facilitated. .

[0018]

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

[Example] Outer diameter 170 mm, inner diameter 158 m
m, length 2580 mm silicon carbide process tube (material: Shin-Etsu Chemical Co., Ltd., SEN-800),
Length of 150 mm, 4 in. A wafer cassette boat (material: same as above) was immersed in a 7% hydrofluoric acid solution for 60 minutes.
This member was taken out of the 7% hydrofluoric acid solution and thoroughly rinsed with pure water.

Then, after drying on a clean bench for 24 hours, the tube was set in a diffusion furnace, the boat was inserted into the tube, and oxygen gas was flown into the tube at 3 liters / minute while increasing the temperature at 6 ° C./minute. The temperature was raised to 1250 ° C. at a temperature rate.

After reaching 1250 ° C., the gas flow was stopped, the inside of the tube was depressurized to 90 Torr by a vacuum pump, the operation of the vacuum pump was stopped, and oxygen gas was supplied at 3 liter / min and hydrochloric acid gas was added at 0.15. Flowed into the tube at liter / min for 3 hours. The above steps from the pressure reduction to the flow of oxygen gas and hydrochloric acid gas are repeated twice, the pressure is reduced to 90 Torr again, and then the vacuum pump is stopped.
Then, only oxygen gas was flowed at the same flow rate as above for 4 hours to complete the cleaning.

[Comparative Example] For comparison, a silicon carbide member having the same specifications as those of the example was wet-cleaned under the same conditions as those of the example, and then,
It was set in a diffusion furnace and heated to 1250 ° C. at 6 ° C./min while flowing oxygen gas at 3 liters / min in the same manner as in the example. After reaching 1250 ° C, add 3 liters of oxygen gas /
Minutes, hydrochloric acid gas was flowed through the tube at 0.15 l / min for 48 hours. Then stop the hydrochloric acid gas,
Only oxygen gas was flowed for 48 hours to complete the cleaning.

Si wafers (CZ-P type, CZ-P type) were attached to the process tubes and wafer boats cleaned in the examples and comparative examples.
<111>) was loaded and heat treatment was performed in oxygen at 1150 ° C. for 30 minutes. In order to examine the contamination degree of the Si wafer at this time, the lifetime of the wafer was measured. The results are shown in Table 1. The lifetime of the wafer is longer as the contamination is smaller.

[0024]

[Table 1]

[0025]

According to the present invention, the dry cleaning in the cleaning step of the silicon carbide material can be performed in a short time and with a high cleaning degree, which improves the productivity of the semiconductor and reduces the production cost. be able to.

Claims (1)

[Claims] 1. Cleaning of a silicon carbide-based member, characterized in that after cleaning a silicon carbide-based member for semiconductor production with a dry hydrochloric acid gas, decompressing the residual gas in the system to remove oxygen gas flow cleaning. Method.