Comparison between oxidation processes used to obtain the high inversion channel mobility in 4H-SiC MOSFETs

In this work two oxidation methods aimed at improving the silicon face 4H-SiC/SiO 2 interface are compared. One is an oxidation in N 2 O performed in a quartz tube using quartz sample holders and the other is a dry oxidation performed in an alumina tube using alumina sample holders. In n-type metal oxide semiconductor (MOS) capacitors the interface state density near the SiC conduction band edge is estimated using capacitance–voltage ( C – V ) and thermal dielectric relaxation current (TDRC) measurements. N-channel metal oxide semiconductor field effect transistors (MOSFETs) are characterized by current–voltage ( I – V ) techniques and the inversion channel mobility is extracted. It is shown that the high inversion channel mobility (154 cm 2 V −1 s −1 ) seen in samples oxidized using alumina correlates with a low interface trap density (3.6 × 10 11 cm −2 ). In the case of N 2 O oxidation the mobility is lower (24 cm 2 V −1 s −1 ) and the interface trap density is higher (1.6 × 10 12 cm −2 ). Room temperature C – V measurements are of limited use when studying traps near the conduction band edge in MOS structures while the TDRC measurement technique gives a better estimate of their density.