On the presence of aluminum in thermally grown oxides on 6H-siliconcarbide [power MOSFETs]

N-type and P-type 6H-Silicon carbide wafers, along with P-type silicon control wafers were oxidized in dry oxygen at 1275°C for 45 min. Capacitance-voltage measurements on the SiO₂ films formed on the N-type 6H-SiC and the silicon control wafers yielded near ideal characteristics while the SiO₂ films on P-type 6H-SiC revealed high effective charge and interface state densities. Secondary Ion Mass Spectroscopy performed on the oxides showed significant levels of aluminum and sodium in SiO₂ on both N-type and P-type 6H-SiC but not on the silicon control wafers indicating that neither element was introduced during processing. The presence of aluminum in oxides on both types suggests that it is not solely responsible for the increased effective oxide charge and interface state densities commonly observed in oxides formed on P-type 6H-SiC