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 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 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.

The effect of biaxial strain on the phonon-limited mobility in 4H-SiC MOSFETs

“…They have reported that compressive stress improves mobility due to lighter effective mass. 23,24) However, the tensile stress on 4H-SiC has not received much attention.…”