Evaluation of lateral diffusion factor in silicon from subthreshold current in short-channel vertical SIT test structure

A measurement method for the evaluation of the lateral diffusion factor of deep implanted regions in lightly doped material is proposed. The method is based on measurements of the subthreshold current versus drain voltage in vertical static induction transistor (SIT) devices. The subthreshold current is very sensitive to SIT channel width and hence to lateral diffusion of the gate regions, as shown by two-dimensional numerical analysis. Experimental results obtained for test structures fabricated with different boron doses and the same drive-in treatment indicate a lateral diffusion factor of 64% for a typical drive-in process.<
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