HEAT-INSULATING CYLINDER FOR DEVICE FOR PULLING UP SILICON SINGLE CRYSTAL

摘要

PROBLEM TO BE SOLVED: To provide a highly durable and inexpensive heat-insulating cylinder capable of preventing silicification by the reaction of a graphite material with SiO2 gas so as not to cause the drop of a silicified layer and further capable of preventing the deposition of Si gas. SOLUTION: This heat-insulating cylinder 30 is composed of a graphite base material having an average thermal expansion coefficient of 4.0-6.0×10<-6> / deg.C in a temperature range of room temperature to 1000 deg.C and an average fine pore diameter of >=10000 angstrom in a fine pore diameter range of 75-75000 angstrom measured by a method of mercury penetration. A coating film comprising pyrolytic carbon is formed on the inside surface of the graphite base material at least in the inside upper part of the heat-insulating cylinder 30 to partially expose the surface of the graphite base material.