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 MOSFET (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 (V th) on lateral SiC MOSFET was investigated systematically. The observed change of V th was as large as 40 mV with a stress of 170 MPa. By comparing with flat-band voltage (V fb), it was concluded that a change in V th mainly consists of change in V fb on n-MOS capacitor with mechanical stress. Even though the possible origins of such V fb 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.