The piezojunction effect in NPN and PNP vertical transistors and its influence on silicon temperature sensors

This paper describes a test structure to characterize the piezojunction effect for the base-emitter voltage V-BE and the PTAT voltage Delta V-BE. The piezojunction effect directly affects the accuracy of temperature sensors and special types of pressure sensors. Packaging is a source of mechanical stress in electronics circuits. Measurements have been performed for two types of vertical bipolar transistors. Firstly. an NPN transistor of a BiCMOS technology and secondly, a PNP substrate transistor of a CMOS technology, both of them using a [100] silicon wafer geometry. It has been found that the sensitivity for the uniaxial stress of the V-BE of the PNP is four times less than that of the NPN transistor. In both cases. the PTAT voltage appears to be hardly stress-sensitive. (C) 2000 Elsevier Science S.A. All rights reserved.