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我们知道,n~+埋层扩散后,接着进行N-型外延层的生长,并把它作为集成电路中晶体管的集电极用。 由此可见,外延层质量对电路性能有相当大的影响。事实上,电路中所有元件都是制作在这个N-型外延层中,而不是衬底中。 然而,要作出特性好的外延片,石墨基座的处理又是头等重要的问题之一。 我们采用渗硅法处理石墨。石墨结构的松紧对渗硅有很大的影响。结构松的石墨能渗入很多的硅,但大量硅渗入后,由于膨胀系数的不同常造成断裂。结构紧的石墨硅很难渗入,只能在石墨表面熔掉堆结。
We know that after the n ~ + buried layer is diffused, the N-type epitaxial layer is grown and used as the collector of the transistor in the integrated circuit. Thus, the quality of the epitaxial layer has a considerable impact on the circuit performance. In fact, all the components in the circuit are made in this N-type epitaxial layer, not in the substrate. However, to make good epitaxial wafers, the handling of the graphite base is one of the top priorities. We use silicon infiltration graphite. Elastic graphite structure on the infiltration of silicon has a great impact. Structure of loose graphite can penetrate a lot of silicon, but after a large number of silicon infiltration, often due to the different expansion coefficient of rupture. Structure tight graphite silicon is difficult to penetrate, only melted in the graphite pile surface.