Increased current gain and suppression of peripheral base currents in silicide self-aligned narrow-width polysilicon-emitter transistors of an advanced BiCMOS technology

Silicidation of the emitter and base regions of the bipolar transistors of an advanced single-level polysilicon BiCMOS (bipolar complementary metal oxide semiconductor) technology is observed to result in an anomalously strong dependence of common-emitter current gain on emitter width. This effect is attributed to an increase in the peripheral component of the base current associated with the silicide extrinsic base at the periphery of the emitter. It is demonstrated that the current gain of silicide narrow-emitter transistors may be doubled by the introduction of a lightly doped extrinsic base region (LDEB) below the oxide-sidewall spacer. Further improvement by a factor of 2-3 may be achieved by increasing the width of the oxide-sidewall spacer.<>