Enhancement of channel mobility in 4H-SiC trench MOSFET by inducing stress at SiO2/SiC gate interface

Abstract

To investigate the impact of stress at the SiO2/SiC gate interface on the channel mobility of 4H-SiC trench MOSFETs, we fabricated trench MOSFETs with two variations of stress in the channel region by changing the deposition temperature of polycrystalline silicon used for gate electrodes. The results found that effective mobility was enhanced by several dozen MPa of tensile stress toward [ 1 1 ¯ 00 ] induced by the polycrystalline silicon. Based on the temperature dependence of mobility, all scattering mobilities were enhanced. It was supposed that the electron effective mass decreased because of tensile stress induced at the channel region.