High-temperature operation of SiC planar ACCUFET

In this paper, the authors discuss the high-temperature characteristics of novel planar vertical MOSFET structures (called ACCUFETs) fabricated from 6H-SiC and 4H-SiC polytypes. A room-temperature specific on-resistance (R_on,sp) of 18 mΩ·cm² 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 mΩ·cm² obtained in simulations. The measured R_on,sp for the 6H-SiC ACCUFET is within 2.5× 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/cm² was 0.9 V, which is much less than that of a 1200-V insulated gate bipolar transistor (typically, 3 V for a high-speed device). The R_on,sp exhibits 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 R_on,sp for the best 4H-SiC reduced rapidly with increase in temperature. At room temperature, the unterminated 6H-SiC and 4H-SiC devices had a breakdown voltage of 350 V and 450 V, respectively, with a leakage current of <100 μA