Growth of Gate Oxides on 4H-SiC by NO at Low Partial Pressures

In an attempt to significantly reduce the amount of nitric oxide (NO), commonly used to improve the quality of gate oxides on 4H–SiC, a series of alternative gate oxidation processes using a combination of O2 and NO gas mixtures at low partial pressures were investigated. The properties of 4H–SiC/SiO2 interfaces on n-type MOS capacitors were examined by the measurement of accumulation conductances over a range of frequencies. Oxide integrity was evaluated by current–voltage measurements and by the extraction of the conduction band offset barrier heights through Fowler–Nordheim (F–N) analysis. A notable reduction of accumulation conductance, indicating a reduction of near-interface traps (NITs), was observed over all measured frequencies for oxidation processes containing NO with a partial-pressure of only 2%. Gate oxides grown in mixture of O2 and NO at low-partial-pressures demonstrated a considerable improvement of dielectric properties, increasing the barrier height to near theoretical values.