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/SiO2 interface are compared. One is an oxidation in N2O 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 x 10(11) cm(-2)). In the case of N2O oxidation the mobility is lower (24 cm(2) V-1 s(-1)) and the interface trap density is higher (1.6 x 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.