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一、问题的提出众所周知,生产中硅PNP管与硅NPN管β的控制范围,前者是很离散的,通常同一大圆片上β范围有时可以从20到200都有,最大不均匀性达90%左右.而后者则比较容易控制在一定的范围之中,最大不均匀性一般只有30%左右.造成上述差别的主要原因,在于由于管子极性不同,基区选择的掺杂不同造成.在硅NPN管中,基区扩散的杂质源往往是硼,而在硅PNP管中,恰恰相反,基区扩散的杂质源往往为磷.由于在同一温度下,磷的扩散系数比硼的扩散系数大,所以在低浓度的基区扩散中,
First, the problem raised As we all know, the production of silicon PNP tube and silicon NPN tube β control range, the former is very discrete, usually on the same large wafer β range can sometimes have from 20 to 200, the maximum non-uniformity of about 90% While the latter is relatively easy to control in a certain range, the maximum non-uniformity is generally only about 30% .This difference is mainly due to the different polarities of the tubes, the choice of different base doping caused in the silicon NPN In the tube, the source of the impurity diffused in the base region is often boron, whereas in the silicon PNP tube, on the contrary, the source of impurity diffused in the base region is often phosphorus. Since the diffusion coefficient of phosphorus is larger than the diffusion coefficient of boron at the same temperature, So in the low concentration of the proliferation of base area,