Experimental investigation of piezojunction effect in silicon and its temperature dependence

Owing to the piezojunction effect, mechanical stress is a dominant cause of inaccuracy and long-term instability in the base-emitter voltage of integrated bipolar transistors. This effect directly affects the accuracy of important basic circuits such as bandgap voltage references and temperature sensors. Novel results are presented of an experimental investigation of the piezojunction effect and its temperature dependence for vertical bipolar transistors produced in a standard {001}-oriented silicon wafer. It is found that the piezojunction effect can be well characterised with a second-order equation including the piezojunction coefficients. Experimental investigation shows that the piezojunction coefficients decrease with increasing temperature