Comparative study of mechanical stress-induced flat-band voltage change in MOS capacitor and threshold voltage change in MOSFET fabricated on 4H-SiC (0001)

Abstract

The impact of mechanical uniaxial stress on electrical characteristics of 4H-SiC (0001) n-type metal-oxide-semiconductor field-effect transistor (n-MOSFET) was systematically investigated by a mechanical 4-point bending method. Expected variation of field-effect mobility with stress was observed and for the first time, a direct relationship between uniaxial stress and significant change in threshold voltage (Vth) on lateral SiC MOSFET was investigated systematically. The observed change of Vth was as large as 40 mV with the stress of 170 MPa. By comparing with flat-band voltage (Vfb), it was concluded that change in Vth mainly consists of change in Vfb on n-MOS capacitor with mechanical stress. Even though possible origins of such Vfb change with stress are not clarified yet, they were suggested to be either the change in band alignment or the change in fixed charge density induced by electronic structure change.