Negative Impact of Compressive Biaxial Stress on High Precision Bipolar Devices

Abstract

Some packaging technologies of electronic devices introduce compressive biaxial stress and variable vertical stress. In unipolar MOS devices, stress variations typically only linearly affect drain current via carrier mobility. Collector currents of bipolar devices are additionally affected by variations in intrinsic carrier concentration. This leads to increased variability of key device parameters in the compressive stress regime. Reducing package-induced compressive stress, or inducing tensile stress, should improve device variability due to local stress variations.