Trench-proximity effects on collector current in self-aligned NPN and PNP bipolar transistors

As lithographic ground rules are scaled into the deep sub-micron regime in today's VLSI technologies, the proximity of different materials in a given device structure often induces significant mechanical stress. In this paper, we report the observation of the collector current (Ic) variation induced by the isolation trench in advanced bipolar devices. It is shown that as the trench-intrinsic device separation is pushed into deep sub-micron regime, Ic decreases in the npn transistors, while it increases in the pnp transistors. We attribute the latter to an in-plane biaxial tensile stress which lowers the electron mobiity while enhances the hole mobility in the 〈001〉 (vertical) crystal orientation. © 1994.