Abstract: A sidewall passivation layer is deposited on an etched feature in a semiconductor substrate with a hydrocarbon deposition gas by introducing H2, determining certain mixture percentages for the hydrocarbon gas/H2 mix at which the etch rate for the substrate peaks, the etch rate begins to rise from a generally steady state, and/or the etch rate falls to zero, and then maintaining the mixture percentage within a selected range. Where the hydrocarbon gas/H2 mix is maintained at a percentage between the steady-state etch rate percentage and the peak etch rate percentage, then relatively high ion energies are used. Where the hydrocarbon gas/H2 mix is maintained at a percentage between the peak etch rate percentage and the percentage where the etch rate falls to zero, then relatively low ion energies are used.

Abstract: This invention relates to methods for treatment of semiconductor substrates and in particular a method of etching a trench in a semiconductor substrate in a reactor chamber using alternatively reactive ion etching and depositing a passivation layer by chemical vapour deposition, wherein one or more of the following parameters: gas flow rates, chamber pressure, plasma power, substrate bias, etch rate, deposition rate, cycle time and etching/deposition ratio vary with time.