Oxide deposition followed by high-temperature annealing in N2O has been investigated to
improve the quality of 4H-SiC MOS structures. Annealing of deposited oxides in N2O at 1300oC
significantly enhances the breakdown strength and decreases the interface state density to 3x1011
cm-2eV-1 at EC – 0.2 eV. As a result, high channel mobility of 34 cm2/Vs and 52 cm2/Vs has been
attained for inversion-type MOSFETs fabricated on 4H-SiC(0001)Si and (000-1)C faces, respectively.
The channel mobility shows a maximum when the increase of oxide thickness during N2O annealing
is approximately 5 nm. A lateral RESURF MOSFET with gate oxides formed by the proposed process
has blocked 1450 V and showed a low on-resistance of 75 mcm2, which is one of the best
performances among lateral SiC MOSFETs reported.