Quality of gate oxides grown on state-of-the-art SIMOX and ZMR SOI substrates

The quality of 25-nm gate oxides formed on state-of-the-art SIMOX and ZMR silicon-on-insulator (SOI) substrates was studied using NMOSFETs. Circular, edgeless, and conventional island isolated devices were used. Devices fabricated on bulk silicon wafers were studied for comparison. I-V characteristics, breakdown voltages, charge trapping, and charge to breakdown were characterized. The results clearly demonstrated that the quality of SIMOX and ZMR wafers and especially of the top Si surface was as good as that of bulk silicon. The quality of the gate oxides formed on island isolated devices was poor due to defective oxide formed on the sidewalls. A comparison of circular, edgeless MOSFETs and island isolated MOSFETs can be used to optimize island etching, sidewall cleaning, and gate oxidation processes.<
>