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业已发现,对于硼在砷扩散层下面的情况来说,在低温热处理期间,砷的扩散被加速了。其扩散系数与一般扩散系数相比是非常之大的,而且与处理时间有关。在700℃、5小时的扩散条件下,砷的有效扩散系数是1×10~(-16)厘米~2/秒,对于700℃、170小时的扩散,其有效扩散系数为7×10~(-18)厘米~2/秒。这样一种现象可能是由于在这些处理过程中形成过量的空位。对于以砷做发射极掺杂剂的 npn 晶体管说来,这也会引起发射极陷落效应。
It has been found that the diffusion of arsenic is accelerated during low temperature heat treatment for the case where boron is below the arsenic diffusion layer. The diffusion coefficient and the general diffusion coefficient is very large compared to, and with the processing time. The effective diffusion coefficient of arsenic is 1 × 10 ~ (-16) cm ~ 2 / s under the condition of 700 ℃ for 5 hours, and the diffusion coefficient is 7 × 10 ~ (-1) for 170 hours at 700 ℃ -18) cm ~ 2 / sec. Such a phenomenon may be due to the formation of excess space during these processes. For npn transistors that use arsenic as emitter dopant, this also causes the emitter fall-off effect.