SiC-DACFET

Abstract

The nm-range abrupt doping profiles in SiC epitaxial layers are stable even after the high temperature process because SiC crystal exhibits little diffusion of impurities. Growth of the SiC delta-doped layers have been reported by our group and the others. We believe that the well-designed delta-doped epitaxial layers for the FET channels extend possibility of the power SiC FET. We proposed the SiC Delta-doped Accumulation Channel MOSFET (DACFET) consisting of the delta-doped layers for MOS channel and reported its high MOS-channel mobility. The vertical hot-wall-type CVD system was used to grow SiC epitaxial layers. The pulse valve, which supplied short (<ms) gas pulse flow, was directly connected to the CVD reactor to introduce the doping gases N 2. The pulse-doping technique enabled formation of the delta-doped-layer structure during SiC epitaxial growth. The n-type delta-doped layer as thin as 2 nm was fabricated with a peak N concentration of 1 × 10 19 cm −3. The electrical characteristics of the DACFET, for example threshold voltage and R on, can be tuned by controlling the delta-doped-layer structures in MOS channel. MOS-channel mobility of the normally-off lateral DACFET was measured to be >100 cm 2/V s. The vertical DACFET, whose blocking voltage was >600 V, was fabricated with the double-implantation MOS process. R on of the normally-off 2 μm-gate DACFET was measured to be 13 mΩ cm 2. Current density was observed to be >140 A cm −2 larger than Si-IGBT. Shortening of gate length and unit cell size of the SiC-DACFET using high-resolution lithography will result in R on <7 mΩ cm 2.