Base-emitter voltage mismatch in a pair of self-aligned bipolar transistors

The base-emitter voltage mismatch. ΔV_BE for a pair of double polysilicon self-aligned bipolar transistors is studied. In the low emitter current range, the base peripheral effect is a dominant factor affecting ΔV_BE. Since the base peripheral component caused by the lateral encroachment of the extrinsic base on the emitter region becomes important, ΔV_BE increases as sidewall spacer width decreases. On the other hand, in the high current range, the emitter contact resistance is dominant and ΔV_BE increases due to increased mismatch of emitter resistance