国内生产的外延片往往由于外延基座的原因造成“自掺杂”。近年来从国外引进的设备中看到外延基座大多标明是碳化硅包复的,LPCVD法直接合成的a-SiC致密性非常高,可以制造出完全不渗透的包复石墨部件,SiC的高温机械强度高,热化学性能稳定,在包复层阻挡杂质扩散能力方面,比热解石墨强,外延时造成“自渗杂”的机会少, Domestically produced epitaxial wafers often result in “self-doping” due to the epitaxial base. In recent years, the introduction of foreign equipment seen in the epitaxial base are mostly marked silicon carbide cladding, LPCVD direct synthesis of a-SiC is very high density, can be made completely impermeable coated graphite parts, SiC high temperature High mechanical strength, thermal chemical stability, in the package barrier to block the ability of impurities to diffuse stronger than pyrolytic graphite, epitaxial causes “self-infiltration miscellaneous” less opportunity,