| 摘要 |
PROBLEM TO BE SOLVED: To suppress the occurrence of a warp or break in a dummy wafer in a film formation heat treatment process, by forming a silicified layer at the surface part of a vitreous carbon material, and setting the thickness of this silicified layer in a specified range. SOLUTION: A dummy wafer is made of vitreous carbon material, and the surface layer of this dummy wafer is silicified, whereby a silicified layer is made. The vitreous carbon material is vitreous high hard carbon, and it is abrasion-resistant, and gas-impermeable, and is manufactured by solid-phase carbonization, and it is 2000 deg.C or over in heat-resistance temperature, 1.5-1.6g/cm<3> in bulk specific gravity, and 100MPa or over in flexural strength, and 5-10W/m.K in heat conductivity, and the one which has a thermal expansion coefficient of 3.0-3.5×10<-6> / deg.C is used. Moreover, the porosity of vitreous carbon is 0.01%-5%. Then, the thickness of the silicified layer being made is within the range of 0.5-2μm though it changes, depending upon the reaction time between SiO2 and the vitreous carbon material, the porosity of the vitreous carbon material, etc.
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