JP2003277933A - Method of purifying silicon carbide-coated member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of purifying a silicon carbide-coated member in which the purity of a silicon carbide coating layer can easily be enhanced in a short time at a low cost in order to prevent the outward diffusion of impurities and the contamination of a wafer or the like even when a silicon carbide- coated member is used at high temperatures for a long period of time in a semiconductor heat treatment process. <P>SOLUTION: In the silicon carbide-coated member, impurities present on the surface layer of the silicon carbide coating layer are removed together with silicon carbide in the surface layer by etching treatment using gaseous chlorine trifluoride. <P>COPYRIGHT: (C)2004,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 purifying a silicon carbide-coated member, and more specifically, for a member coated with silicon carbide, the silicon carbide coating layer has a high purity and is used as a jig for semiconductor heat treatment. The present invention relates to a method for purifying a silicon carbide coated member capable of obtaining a suitable member.

[0002]

2. Description of the Related Art In order to supply high quality products in semiconductor manufacturing, it is important to avoid contamination by impurity metals such as wafers and particles. That is, the contamination with the impurity metal or the like causes a reduction in the yield of semiconductor products such as generation of crystal defects in the wafer, abnormal growth of crystals, change in resistance value, change in breakdown voltage, and the like.

In order to avoid the above-mentioned contamination and to improve the yield of semiconductor products and ensure stable operation, wafer boats, boat tables, furnace core tubes, susceptors and trays used in the heat treatment process for silicon wafers and the like. Conventionally, a jig for semiconductor heat treatment such as silica glass (SiO ₂ ) material that generates relatively few particles, a silicon carbide material coated with a high-purity and dense silicon carbide (SiC) film, and a silicon-carbonized material. Silicon (Si-SiC) composite material,
Ceramic members such as carbon (C) materials have been used.

Of these, the quartz glass material is often used as a heat treatment jig for semiconductor manufacturing equipment because it is relatively inexpensive and a high-purity product can be easily obtained.
Since it softens and deforms at 100 ° C or higher, it is limited to use at processing temperatures lower than that. Further, the quartz glass material has low corrosion resistance to a cleaning liquid such as hydrofluoric acid or a mixed acid solution of hydrofluoric acid and nitric acid used in a semiconductor manufacturing process, and is easily corroded and consumed.

In addition, a base material made of a silicon carbide material, a silicon-silicon carbide composite material, a carbon material, a silicon material, or the like,
The silicon carbide-coated ceramic member coated with silicon carbide in the same manner as described above can be stably used even at a high temperature of 1200 ° C. or higher, has excellent corrosion resistance to the hydrofluoric acid, mixed acid, and the like, and has excellent durability. It has the advantage of being excellent. Therefore, in the case of a heat treatment jig used in a high temperature region, the silicon carbide-coated ceramic member is mainly used although the cost is higher than that of the quartz glass material.

Further, in recent years, the degree of integration of semiconductor circuit elements has increased, and even in a low-temperature process, a semiconductor manufacturing member coated with high-purity and dense silicon carbide has come to be used. For example, in the heat treatment process for forming a polysilicon film, an oxide film, a nitride film, etc. on the surface of a silicon wafer, a film is deposited and formed not only on the surface of the silicon wafer but also on the surface of the jig for semiconductor manufacturing, and repeatedly. With use, the deposited film accumulates. Due to the difference in the coefficient of thermal expansion from that of the semiconductor manufacturing jig, these deposited films are separated and become particles, which contaminate the product wafer. For this reason, it is necessary to regularly clean the member to remove the deposited film.

As the degree of integration of semiconductor circuit elements increases, it is necessary to remove even finer particles, and the cleaning cycle for removing the deposited film becomes shorter. Therefore, even if the initial cost is high, the mixed acid or the like can be used. There are an increasing number of cases where silicon carbide-coated ceramic members having corrosion resistance to the cleaning liquid are used.

Conventionally, after the surface of a member coated with such a high-purity and dense silicon carbide film has been cleaned by wet cleaning with hydrofluoric acid solution or the like, dry cleaning with hydrogen chloride gas or the like, , Was shipped and used as a product.

[0009]

However, although the particles and the like adhering to the surface of the silicon carbide coating layer can be removed by the above-mentioned cleaning, impurities existing in the bulk of the silicon carbide coating layer cannot be removed. , Can hardly be removed. This is because the silicon carbide coating layer is
Although it has characteristics of excellent heat resistance, denseness, and corrosion resistance, it is because the diffusion coefficient of impurities in silicon carbide is small, and therefore the effect of removing impurities becomes extremely low.

By the way, in the usual silicon carbide-coated ceramic member, most of the impurities contained therein, including those formed by the CVD method, exist near the surface of the coating layer (surface layer portion). Since the impurities in the surface layer portion are not removed by the cleaning as described above, there has been a disadvantage that the impurities diffuse to the outside in a high temperature heat treatment step or when used for a long period of time.

The present invention has been made in order to solve the above technical problems, and in a semiconductor heat treatment step, even if the silicon carbide coated member is used for a long period of time at a high temperature, impurities are diffused outward. In order to prevent contamination of wafers and the like, it is an object of the present invention to provide a method for purifying a silicon carbide coating member, which can easily and highly purify the silicon carbide coating layer at low cost in a short time. It is a thing.

[0012]

A method for purifying a silicon carbide-coated member according to the present invention is a method for purifying a member coated with silicon carbide by subjecting the member coated with silicon carbide to an etching treatment using chlorine trifluoride gas to form a surface layer of the silicon carbide-coated layer. It is characterized in that impurities existing in the part are removed together with silicon carbide in the surface layer part. According to the present invention, by selectively using chlorine trifluoride (ClF ₃ ) gas as an etching gas, the high impurity content layer can be removed inexpensively and in a short time.
Thereby, the silicon carbide coated member can be easily purified.

The etching treatment is performed at 20 ° C. or higher 600
It is preferably performed at a temperature of not more than ° C. From the viewpoint that the etching rate of the silicon carbide coating layer is appropriate, the etching treatment can be performed while maintaining the in-plane homogeneity, and the etching thickness can be easily adjusted, the treatment temperature within the above range. It is preferable to carry out the etching treatment.

The thickness of the silicon carbide coating layer removed by the etching treatment is preferably 0.1 μm or more and 5 μm or less. By removing the silicon carbide coating layer with a thickness within the above range, the impurity-rich layer in the surface layer portion of the silicon carbide coating layer is surely removed in a state where the in-plane uniformity of the etching progress is maintained. be able to.

The silicon carbide coated member can be preferably used in a jig for heat treatment of semiconductors. By the etching treatment, the impurity concentration of the surface layer portion of the silicon carbide coating layer,
Since it is suppressed to the concentration level in the bulk of the high-purity coating layer, even when the silicon carbide coating member is used for a long period of time under high temperature conditions like a semiconductor heat treatment jig,
There is no outward diffusion of impurities and it is possible to prevent pollution of the surrounding environment.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The method for purifying a silicon carbide-coated member according to the present invention is, for a member coated with silicon carbide, an etching treatment using a chlorine trifluoride gas to remove impurities present in the surface layer portion of the silicon carbide-coated layer from the surface layer. It is characterized in that it is removed together with a portion of silicon carbide. That is, the purification method according to the present invention removes impurities existing in the surface layer portion of the silicon carbide coating layer formed by the CVD method or the like,
The entire silicon carbide coating layer is removed by an etching process. At that time, a characteristic feature is that chlorine trifluoride (ClF ₃ ) gas is selectively used as an etching gas.

Chlorine trifluoride (ClF ₃ ) has a melting point of −7.
It has a color of 6.32 ° C and a boiling point of 11.7 ° C, and is colorless in any of gas, liquid and solid, but when heated, ClF ₃ → ClF + F
Dissociate into ₂ . Further, it is extremely highly reactive and has the characteristic of reacting very easily with silicon carbide and stable metal oxides. The present invention uses this ClF as an etching gas.
By selectively using ₃ , it is possible to remove the high-impurity content layer inexpensively and in a short time. Conventionally, it has been considered difficult to purify due to its high corrosion resistance and impurity diffusion inhibitory properties. The covering member can be easily purified.

In the etching process, the silicon carbide coating member was subjected to a flow rate of 0.01 to 3 SLM (standard state gas: 1 / m).
in) ClF ₃ gas, more preferably a concentration of 5 to 50
in an inert gas stream containing vol% ClF ₃ at 20 ° C.
The treatment is preferably performed at (room temperature) or higher and 600 ° C. or lower.
If the flow rate of ClF ₃ gas exceeds ₃ SLM, particles will be trapped and blown up in the etching treatment furnace. On the other hand, the flow rate of ClF ₃ gas is 0.0
When it is less than 1 SLM, the temperature uniformity and the etching rate uniformity of the silicon carbide-coated member are likely to be impaired.

If the processing temperature exceeds 600 ° C., not only corrosion in the etching processing furnace cannot be ignored, but also the etching reaction speed is too fast, and it becomes difficult to control the etching thickness, resulting in inhomogeneity. It is easily damaged, and thermal deformation or distortion occurs depending on the shape of the member. On the other hand, when the treatment temperature is lower than 20 ° C., the time required for the etching treatment becomes long and the productivity is lowered.

As described above, the etching treatment with ClF ₃ gas is more preferably carried out in a stream of _{5 to} 50 vol% ClF ₃ -containing inert gas, whereby more reliable and uniform etching can be carried out. .

In the member subjected to the etching treatment as described above, the impurity concentration in the surface layer portion of the silicon carbide coating layer is suppressed to the concentration level in the bulk of the coating layer having high purity.
Therefore, even when the silicon carbide-coated member is used for a long time under high temperature conditions, there is no outdiffusion of impurities,
It is possible to prevent pollution of the surrounding environment.

Further, by the etching treatment, CVD
The surface formed during the crystal growth of the silicon carbide coating layer by the method such as the sharp edges and corners can be removed, and the surface becomes smooth. Can be prevented. For example, the surface roughness Ra of the silicon carbide coating member immediately after the silicon carbide coating layer is formed on the silicon-silicon carbide composite material by the CVD method is 0.8.
Although the surface roughness Ra is about μm, the surface roughness Ra of the member after the purification method according to the present invention is smoothed to about 0.6 μm.

In the present invention, the target silicon carbide-coated member is a member in which a silicon carbide coating layer is formed on the surface of a base material, and is a member that can be dry-etched in a furnace, The shape and type are not particularly limited.
Examples of such members include jigs such as wafer boats, boat tables, furnace core tubes, susceptors, and trays for transferring wafers used in semiconductor manufacturing equipment. In particular, yield due to prevention of contamination of semiconductor products. From the viewpoint of improving the heat treatment, a semiconductor heat treatment jig such as a wafer boat, a furnace core tube, and a susceptor used in a heat treatment process for a silicon wafer is suitable.

Further, as a base material constituting the above-mentioned member coated with silicon carbide, conventionally, it has been generally used, and a thermal expansion to the extent that a silicon carbide coating layer can be formed on the surface without peeling off. Any material having a coefficient may be used. In particular, from the viewpoint of thermal stability in the processing furnace, strength, etc., it is preferably any of silicon carbide material, silicon-silicon carbide composite material, silica material, carbon material, and silicon material.

The method for forming the silicon carbide coating layer for coating the surface of the base material is not necessarily limited as long as a highly pure and dense thin layer is formed. Therefore, the coating layer may be formed by any one of physical vapor deposition (PVD) methods such as vapor deposition and sputter deposition, chemical vapor deposition (CVD) methods, and liquid phase deposition (LPD) methods. Absent. Of these, the protective effect of the coating layer can be sufficiently exerted 20
A high-purity and dense silicon carbide film with a thickness of about μm or more can be easily formed with good adhesion to a substrate by the chemical vapor deposition (CVD) method. Is particularly preferable.

In the CVD method, the film (coating layer) raw material is gas phase (gas)
Thin film on the surface of the substrate by chemical reaction.
The energy supply that causes the reaction.
Depending on the feeding means, thermal CVD method, plasma CVD method, light C
The silicon carbide coating according to the present invention is classified into the VD method and the like.
The member may be formed by any method.
For example, by a thermal CVD method, a silicon-silicon carbide composite is formed.
When forming a silicon carbide coating layer on a substrate made of material,
SiCl as supply gas_Four And CH_Four , C₃ H ₈ Low as
Grade hydrocarbon gas and H₂ Using 1000 to 1400
Repeat the process of treating at about ℃ for about 1 hour multiple times
By doing so, a silicon carbide coating layer having a predetermined thickness can be formed.
You can

The thickness of the above-mentioned silicon carbide coating layer depends on the corrosion resistance,
The thickness is preferably 30 μm or more and 200 μm or less from the viewpoints of the effect of protecting the base material such as abrasion resistance, the prevention of peeling due to thermal shock, and the cost.

The thickness of the silicon carbide coating layer removed by the etching treatment is preferably 0.1 μm or more and 5 μm or less. When the thickness of the coating layer to be removed is less than 0.1 μm, the high impurity content layer in the surface layer portion is not reliably removed and remains in the surface layer portion. On the other hand, if the thickness of the coating layer to be removed exceeds 5 μm, it becomes difficult to maintain the in-plane uniformity of the progress of etching.

Furthermore, after applying the purifying method of the present invention to the used member, a silicon carbide coating layer is reformed on the surface of the member by the CVD method or the like, and then the purifying method of the present invention is applied again. As a result, the member can be regenerated. For example, in a member where the surface of the silicon carbide coating layer is damaged and deteriorated due to long-term use and cannot be used, and it is difficult to re-form a high-purity and smooth silicon carbide coating layer on the surface by a CVD method or the like. Even if there is ClF
_A deteriorated silicon carbide coating layer can be removed and purified by an etching treatment in a ₃ gas stream, and then a new silicon carbide coating layer can be reformed. Then, the silicon carbide coating member can be regenerated by applying the purification method of the present invention to the silicon carbide coating layer again.

[0030]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by the following examples. [Example] A substrate of 3 mm x 4 mm x 60 mm made of Si-SiC composite material (TPSS manufactured by Toshiba Ceramics Co., Ltd.) was used to form a Si film having a thickness of about 100 µm by the CVD method.
A sample piece having a C coating layer was prepared. This sample piece was put into a dry etching treatment furnace, and at 350 ° C., ClF ₃
It was treated with a gas (flow rate 2 SLM) for 20 minutes, washed with HF, and dried. This purified sample piece was placed on one surface of a halved silicon wafer, both wafers were placed in a heating furnace, and each wafer was heated in a dry oxygen atmosphere to a predetermined temperature shown in Table 1 below. After heating and holding at that temperature for 1 hour, it was allowed to cool. After cooling down, impurities (Ni, F
e, Na) increase was measured and both half wafers were compared,
The amount of impurities released from the sample piece was determined. The results are shown in Table 1.

[Comparative Example] A sample piece manufactured in the same manner as in the example was not subjected to etching treatment with ClF ₃ gas, and otherwise the same as in the example, and the amount of increase in impurities in each wafer was measured to obtain a sample. The amount of impurities released from the piece was determined. The results are shown in Table 1.

[0032]

[Table 1]

As shown in Table 1, the wafer subjected to the etching treatment using ClF ₃ gas (Example) was compared with the wafer not subjected to the etching treatment (Comparative Example).
It was confirmed that the amount of released impurity metals when the heat treatment was performed was suppressed. That is, it was confirmed that the etching treatment using ClF ₃ gas is an effective purification method for a silicon carbide-coated wafer.

[0034]

As described above, according to the method for purifying a silicon carbide-coated member of the present invention, the cost is low and the time is short.
The member can be easily purified. Further, the member treated by this method, when the impurity concentration of the surface layer portion of the silicon carbide coating layer is suppressed to the concentration level in the bulk of the coating layer of high purity, when used for a long time under high temperature conditions Also, there is no outward diffusion of impurities and it is possible to prevent pollution of the surrounding environment. Therefore, the purification method according to the present invention can be suitably used for a semiconductor heat treatment jig.
Furthermore, even for a silicon carbide-coated member that has been damaged and deteriorated by long-term use, by applying the purification method according to the present invention, a new silicon carbide-coated layer can be formed again and the member can be regenerated. .

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomohide Otsuka             378 Oguni Town, Oguni Town, Nishiokitama District, Yamagata Prefecture               Toshiba Ceramics Co., Ltd. Oguni Office F-term (reference) 4K030 AA03 AA09 AA17 BA37 CA05                       DA08 FA10 LA15

Claims (4)

[Claims] 1. A member coated with silicon carbide is subjected to etching treatment using chlorine trifluoride gas,
A method for purifying a silicon carbide-coated member, characterized in that impurities present in the surface layer portion of the silicon carbide coating layer are removed together with silicon carbide in the surface layer portion. 2. The etching treatment is performed at 20 ° C. or higher and 60 ° C.
The method for purifying a silicon carbide-coated member according to claim 1, wherein the method is performed at 0 ° C or lower. 3. The method for purifying a silicon carbide coated member according to claim 1, wherein the silicon carbide coated layer removed by the etching treatment has a thickness of 0.1 μm or more and 5 μm or less. 4. The method for purifying a silicon carbide coated member according to any one of claims 1 to 3, wherein the silicon carbide coated member is used in a semiconductor heat treatment jig.