JPH11102847A - Dummy wafer made of glassy carbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive to make a dummy wafer superior also in corrosion resistance and to contrive to make the dummy wafer also superior in mirror property and a strength manner in a high purity by a method, wherein the dummy wafer is constituted of a glassy carbon of a specified amount of an ash content or less. SOLUTION: A dummy wafer made of a glassy carbon consists of a glassy carbon of the amount of an ash content of 18 pppm or less. A curing agent and a plasticizing agent are added to a thermoset resin for mixing the thermoset resin with the curing agent and the plasticizing agent. Thereafter, this mixture is injected into a molding die, is held there for one to five days at a temperature of 45 to 55 deg.C, is held for one to five days at a temperature of 65 to 75 deg.C, and moreover is held for one to five days at a temperature of 85 to 90 deg.C obtain a resin molded material cured into a prescribed shape. This resin molded material is further cured for one to five days at a temperature of 130 to 200 deg.C. Then, the molded material is carbonized by calcing at a temperature of 900 to 1,100 deg.C under an inert atmosphere (normally, under an atmosphere, which consists of at least one kind of gas which is chosen from among inert gases, such as helium and argon and non-oxidizing gas, such as nitrogen, hydrogen and halogen gas, and does not contain oxygen, under a reduced pressure or vacuum) using a high-purity graphite jig and a furnace. Moreover, the resin-molded material is subjected to a high-temperature treatment for one to 20 hours at a temperature of 1,100 to 3,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glassy carbon dummy wafer used in the same process as a silicon wafer for the purpose of testing the operation of jigs and machines in an IC manufacturing process.

[0002]

2. Description of the Related Art A semiconductor manufacturing line is required to have a high level of processing accuracy and cleanliness as wiring becomes finer.
Therefore, in a semiconductor manufacturing line, a silicon wafer mirror-finished in the same manner as a product is used as a dummy wafer as a wafer for testing various test items. Since the semiconductor manufacturing process includes approximately 100 processes, a large number of dummy wafers are required. When a silicon wafer is used as a dummy wafer, when a film formed on the dummy wafer is subjected to an etching process, the silicon wafer is also etched, and the surface is roughened, requiring repolishing.
However, there is a limit to the number of times the silicon wafer can be used because the thickness of the silicon wafer is reduced by repolishing. For this reason, a wafer made of a material instead of silicon is required as a dummy wafer.

[0003] The properties required for a material replacing silicon are that they do not contain alkalis and metals or, even if they do, do not release them to the process line. In addition, strong corrosion resistance that can withstand a wet etching process using hydrofluoric acid or nitric acid and a dry etching process using freon gas or hydrochloric acid gas is required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dummy wafer made of glassy carbon which is excellent in corrosion resistance, high in purity, and excellent in specularity and strength.

[0005]

That is, the present invention provides a glassy carbon dummy wafer made of glassy carbon having an ash content of 18 ppm or less.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The glassy carbon dummy wafer of the present invention is made of glassy carbon having an ash content of 18 ppm or less. If the ash content exceeds 18 ppm, the surroundings are contaminated, which is not preferable. It is more preferably at most 10 ppm, further preferably at most 5 ppm. Here, the ash content uses a value measured by the graphite ash measurement method of JIS-R-7223. The ash content of glassy carbon is 18 ppm.
The following is a method of preventing external contamination by calcining and carbonizing using a highly refined graphite jig,
It is performed by a method using a highly purified raw material resin, a method of setting a high processing temperature at the time of manufacturing a glassy carbon dummy wafer, or the like. Hereinafter, preferred examples of the method for producing the glassy carbon dummy wafer of the present invention will be specifically described.

First, a curing agent and a plasticizer are added to a thermosetting resin and mixed well, and then the mixture is poured into a molding die.
It is kept at a temperature of 5 to 55 ° C for 1 to 5 days, at a temperature of 65 to 75 ° C for 1 to 5 days, and further at a temperature of 85 to 90 ° C for 1 to 5 days to obtain a resin molded body cured into a predetermined shape. The resin molded body is further cured at a temperature of 130 to 200 ° C. for 1 to 5 days. Then, using a high-purity graphite jig and a furnace, under an inert atmosphere (usually, oxygen consisting of at least one kind of gas selected from an inert gas such as helium and argon and a non-oxidizing gas such as nitrogen, hydrogen and halogen gas). 900-1,100 ° C under reduced pressure or vacuum under an atmosphere not containing
At a temperature of. 1,100 ° C ~ 3,000
By performing high temperature treatment at a temperature of 1 ° C. for 1 to 20 hours, glassy carbon is obtained.

The processing temperature for obtaining glassy carbon in the present invention is preferably 1,500 to 2,800 ° C., more preferably 1,700 to 2,300 ° C., and further preferably 1,700 to 2,000 ° C. It is. If the temperature is lower than 1,500 ° C., the surface roughness during use tends to decrease, so that the number of use of the dummy wafer tends to decrease. If the temperature exceeds 2,800 ° C., the mechanical strength may decrease. There is a tendency that the strength is insufficient, and destruction or deformation is increased at the time of processing, which makes actual use difficult.

The thermosetting resin used for the production of glassy carbon is not particularly limited, and examples thereof include a furan resin, a phenol resin, an epoxy resin, an unsaturated polyester resin, a melamine resin, an alkyd resin, and a xylene resin. . Further, a mixture of these resins may be used. Preferably, it is a phenol resin or a furan resin or a mixture thereof. When a furan resin is used, a curing agent such as p-toluenesulfonic acid and a plasticizer such as n-butyl phthalate and ethylene glycol are blended. Each of the curing agent and the plasticizer is preferably used in an amount of 0.01 to 20% by weight based on the thermosetting resin.

The obtained glassy carbon molded body is processed into the same shape as a silicon wafer using a drill or the like having a diamond electrodeposited on the tip, and then a double-side polishing machine having a cast iron platen attached to both sides. Then, a mirror-finish is performed using polishing powder to obtain a glassy carbon dummy wafer.
The mirror surface processing method is not limited to the above method.

The apparent density of the glassy carbon in the present invention is preferably 1.48 or more, and the bending strength is preferably 13 or more.
It is more preferable that the pressure is 0 MPa or more, the apparent density is in the range of 1.48 to 1.55, and the bending strength is in the range of 130 to 240 MPa because the surface roughness and the mechanical strength are improved. The apparent density in the above is a value determined by a method according to JIS-R-2701, and the bending strength is a value determined by a method according to JIS-R-7222.

[0012]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Furan resin precondensate (VF-3 manufactured by Hitachi Chemical Co., Ltd.)
03) 0.6 parts by weight of paratoluenesulfonic acid, 10 parts by weight of n-butyl phthalate (Wako Pure Chemical Industries), and 5 parts by weight of ethylene glycol (Wako Pure Chemical Industries) were added to 100 parts by weight, and mixed well. The resin was poured into a mold, dried and cured at 50 ° C. for 3 days, at 70 ° C. for 3 days, at 90 ° C. for 3 days, heated up to 160 ° C. at 5 ° C./h, and kept at 160 ° C. for 3 days. A curing treatment was performed to obtain a disc-shaped resin molded product having a thickness of 2 mm and a diameter of 200 mm. The molded body was placed in an annular furnace, calcined and carbonized at a temperature of 1,300 ° C. for 10 hours in a nitrogen stream, and then heated at a temperature of 1,700 ° C. in an inert atmosphere using a jig and an atmosphere furnace which had been treated to high purity. High temperature treatment was performed for 6 hours to obtain a glassy carbon plate. The ash content of the obtained glassy carbon plate was 5 ppm. The properties are shown in Table 1.

This glassy carbon plate was processed into a disk having a diameter of 150 mm by a diamond processing machine. The disk was primarily polished using a double-side polisher having both surfaces made of cast iron with abrasive grains SiC # 1000, and processed to a thickness of 0.7 mm. Finish polishing is performed by changing the abrasive grains to cerium oxide # 5000, and then cerium oxide # 1.
At 0000, final polishing was performed to obtain a mirror-finished disk having a thickness of 0.6 mm. Surface roughness after polishing is 0.0
It was 06 μm.

A polysilicon film was deposited to a thickness of 10 nm on the mirror-finished glassy carbon plate by a low pressure CVD method. This polysilicon film is treated with a ratio of hydrofluoric acid to nitric acid of 1:
5 was immersed in the mixed solution for about 15 minutes to perform etching to remove the polysilicon film. Table 2 shows the results of examining the change in surface roughness after repeating this operation 10 times. As a result, it was found that there was almost no change. As a comparison, the same experiment was performed using a silicon wafer, and as a result, deterioration of the surface roughness was observed.

Example 2 Furan resin precondensate (VF-3 manufactured by Hitachi Chemical Co., Ltd.)
03) 0.6 parts by weight of paratoluenesulfonic acid and 0.6 parts by weight of ethylene glycol (Wako Pure Chemical Industries) were added to 100 parts by weight, mixed well, and then cured and fired under the same conditions as in Example 1. After that, using a high-purity jig and an atmosphere furnace under an inert atmosphere at a temperature of 1,700 ° C.
A high temperature treatment was performed for a time to obtain a glassy carbon plate. The ash content of the obtained glassy carbon plate was 12 ppm. The properties are shown in Table 1 and the characteristics are shown in Method 2.

This glassy carbon plate was processed into a disk having a diameter of 150 mm by a diamond processing machine. The disk was primarily polished using a double-side polisher having both surfaces made of cast iron, using abrasive grains of SiC # 1000, and processed to a thickness of 0.7 mm. In addition, the abrasive grains are made of cerium oxide with a count of $ 5,000.
Finish polishing is performed in place of cerium oxide.
Final finish polishing at 10,000, thickness 0.6mm
A mirror-finished disk was obtained. The surface roughness after polishing is 0.
003 μm.

On this mirror-finished glassy carbon plate, a polysilicon film was deposited to a thickness of 10 nm by low pressure CVD. This polysilicon film is treated with a ratio of hydrofluoric acid to nitric acid of 1:
5 was immersed in the mixed solution for about 15 minutes to perform etching to remove the polysilicon film. Table 2 shows the results of examining the change in surface roughness after repeating this operation 10 times. As a result, it was found that there was almost no change.

Example 3 Initial condensate of furan resin (VF-3 manufactured by Hitachi Chemical Co., Ltd.)
03) 70 parts by weight and 30 parts by weight of a phenol resin (VP-112N manufactured by Hitachi Chemical Co., Ltd.) were sufficiently mixed at a temperature of 50 ° C., and then cooled to 30 ° C. The mixture 100
0.6 parts by weight of paratoluenesulfonic acid based on parts by weight,
After adding 5 parts by weight of n-butyl phthalate (manufactured by Wako Pure Chemical Industries, Ltd.) and 5 parts by weight of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) and mixing them well, the same conditions as in Example 1 were added. After hardening and baking under high temperature, using a jig and high-purity processing jig and atmosphere furnace, the temperature is 7200
High-temperature treatment was performed for an hour to obtain a glassy carbon plate. The ash content of the obtained glassy carbon plate was 18 ppm. The properties are shown in Table 1.

This glassy carbon plate was processed into a disk having a diameter of 150 mm by a diamond processing machine. The disk was primarily polished using a double-sided polishing machine having both surfaces made of cast iron with abrasive grains of SiC # 1000 and processed to a thickness of 0.7 mm. Furthermore, the finish is polished by changing the abrasive grains to cerium oxide count # 5000, and further to cerium oxide count # 10.
The final finish polishing was performed at 000 to obtain a mirror-finished disk having a thickness of 0.6 mm. Surface roughness after polishing is 0.00
It was 4 μm.

A 10 nm-thick polysilicon film was deposited on the mirror-finished glassy carbon plate by low pressure CVD. This polysilicon film is treated with a ratio of hydrofluoric acid to nitric acid of 1:
5 was immersed in the mixed solution for about 15 minutes to perform etching to remove the polysilicon film. Table 2 shows the results of examining the change in surface roughness after repeating this operation 10 times. As a result, it was found that there was almost no change.

Example 4 Precondensate of furan resin (VF-3 manufactured by Hitachi Chemical Co., Ltd.)
03) 70 parts by weight and 30 parts by weight of a phenol resin (VP-112N manufactured by Hitachi Chemical Co., Ltd.) were sufficiently mixed at a temperature of 50 ° C., and then cooled to 30 ° C. The mixture 100
0.6 parts by weight of paratoluenesulfonic acid based on parts by weight,
After adding 3 parts by weight of n-butyl phthalate (manufactured by Wako Pure Chemical Industries, Ltd.) and 2 parts by weight of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) and mixing well, the same conditions as in Example 1 were used. After curing and firing under a high temperature, a high-temperature treatment was performed at a temperature of 2,800 ° C. for 7 hours in an inert atmosphere using a jig and an atmosphere furnace treated to a high purity to obtain a glassy carbon plate. The ash content of the obtained glassy carbon plate was 3 ppm. The properties are shown in Table 1.

This glassy carbon plate was processed into a disk having a diameter of 150 mm by a diamond processing machine. The disk was primarily polished using a double-sided polishing machine having both surfaces made of cast iron with abrasive grains of SiC # 1000 and processed to a thickness of 0.7 mm. Furthermore, the finish is polished by changing the abrasive grains to cerium oxide count # 5000, and further to cerium oxide count # 10.
000 to obtain a mirror-finished disk having a thickness of 0.6 mm. The surface roughness after polishing is 0.006
μm.

On this mirror-finished glassy carbon plate, a polysilicon film was deposited to a thickness of 10 nm by low pressure CVD. This polysilicon film is treated with a ratio of hydrofluoric acid to nitric acid of 1:
5 was immersed in the mixed solution for about 15 minutes to perform etching to remove the polysilicon film. Table 2 shows the results of examining the change in surface roughness after repeating this operation 10 times. As a result, it was found that there was almost no change.

Comparative Example Furfuryl Alcohol Initial Condensate (Hitachi Chemical Industry Co., Ltd.)
1 part by weight of a 50% by weight aqueous solution of p-toluenesulfonic acid was added to 100 parts by weight of VF-303 (manufactured by VF-303), mixed thoroughly, cured and fired under the same conditions as in Example 1, and then treated with high purity. Using a jig and an atmosphere furnace, high temperature treatment was performed at a temperature of 1,400 ° C. for 10 hours in an inert atmosphere to obtain a glassy carbon plate. The ash content of the obtained glassy carbon plate was 29 ppm. The properties are shown in Table 1.

This glassy carbon plate was processed into a disk having a diameter of 150 mm by a diamond processing machine. The disk was primarily polished using a double-sided polisher having both surfaces made of cast iron with abrasive grains SiC # 1000, and processed to a thickness of 0.7 mm. Finish polishing is performed by changing the abrasive grains to cerium oxide # 5000, and then cerium oxide # 1.
At 0000, final polishing was performed to obtain a mirror-finished disk having a thickness of 0.6 mm. Surface roughness after polishing is 0.0
It was 09 μm.

On this mirror-finished glassy carbon plate, a polysilicon film was deposited to a thickness of 10 nm by low pressure CVD. This polysilicon film is treated with a ratio of hydrofluoric acid to nitric acid of 1:
5 was immersed in the mixed solution for about 15 minutes to perform etching to remove the polysilicon film. Table 2 shows the results of examining the change in surface roughness after repeating this operation 10 times. As a result, the surface roughness was slightly deteriorated.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

The glassy carbon dummy wafer of the present invention has excellent mirror-like properties, is more excellent in corrosion resistance than silicon wafer, and has high mechanical strength. Therefore, it is inexpensive and can be used many times. It is informative.

Claims (2)

[Claims] 1. A glassy carbon dummy wafer comprising glassy carbon having an ash content of 18 ppm or less. 2. The glassy carbon dummy wafer according to claim 1, wherein the apparent density of the glassy carbon is 1.48 or more and the bending strength is 130 MPa or more.