High temperature operation of SiC planar ACCUFET

Power losses in SiC switches can be up to two orders of magnitude lower than those in silicon devices, and hence, SiC devices exhibit a tremendous potential for applications in UPS, motor control, etc. Due to very low diffusion coefficients in SiC, UMOSFETs have been fabricated, but their performance has been limited by premature oxide breakdown and low inversion layer mobility. A novel planar vertical MOSFET structure (called ACCUFET), which eliminates both these problems, has been proposed. In this paper, the authors discuss high temperature characteristics of ACCUFETs fabricated from 6H-SiC and 4H-SiC polytypes. A room temperature specific on-resistance (R/sub on,sp/) of 18 m/spl Omega/-cm/sup 2/ was measured on the best 6H-SiC device at a logic-level gate drive voltage of only 5 V, which was in excellent agreement with 15 m/spl Omega/-cm/sup 2/ obtained in simulations. The measured R/sub on,sp/ for the 6H-SiC ACCUFET is within 2.5/spl times/ of the drift region resistance which is the best value obtained so far for any high voltage SiC MOSFET. The forward voltage drop of the best 6H-SiC ACCUFET at 50 A/cm/sup 2/ was 0.9 V, which is much less than that of a 1200 V IGBT (typically 3 V for a high speed device). The R/sub on,sp/ exhibited a positive temperature coefficient, which is extremely desirable since it allows paralleling of devices and also improves reliability by avoiding current filamentation problems. In contrast, the room R/sub on,sp/ for the best 4H-SiC reduced rapidly with increase in temperature to 128 m/spl Omega/-cm/sup 2/ at 450 K. At room temperature, the unterminated 6H-SiC and 4H-SiC devices had a breakdown voltage (BV) of 350 V and 450 V, respectively, with a leakage current of