Silicon or silicon carbide tube with semiconductive coating - providing direct heating for diffusion processes in semiconductor technology

摘要

Directly heated silicon or SiC tubes are produced by applying onto their outer surface (or at least a part of it) a powder or paste contg. a strongly doped Si, and firing to form a semiconductive coating. The Si powder to be applied as a semiconductive coating is pref. doped with B, P, As, or Sb to such an extent that the resistance of the silicon drops to 10 m omega cm. The firing temp. is >=1400 degrees C. The thickness of the semiconductive coating is >=0.5 mm. The tube is prepd. by deposition of Si or SiC from the gas phase (SiHCl3 or SiHCl2CH3) onto a graphite mandrel. A uniformly conducting coating is formed, which additionally enhances the gas-impermeability of the tube.