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

Abstract

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.