Realization of low on-resistance 4H-SiC power MOSFETs by using retrograde profile in P-body

Inversion-type 4H-SiC power MOSFETs using p-body implanted with retrograde profiles have been fabricated. The Al concentration at the p-body surface (Nas) is varied in the range from 5×1015 to 2×1018 cm-3. The MOSFETs show normally-off characteristics. While the Ron is 3 cm2 at Eox = (Vg-Vth)/dox ≅ 3 MV/cm for the MOSFET with the Nas of 2×1018 cm-3, the Ron is reduced by a decrease in the Nas and 26 mcm2 is attained for the device with the Nas of 5×1015 cm-3. The inversion channel mobility and threshold voltage are improved with a decrease in the Nas. By modifying the structural parameter of the MOSFET, a still smaller Ron of 7 mcm2 is achieved with a blocking voltage of 1.3 kV.