Effect of substrate temperature on dry etching of InP, GaAs, and AlGaAs in iodine- and bromine-based plasmas

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Abstract
Electron cyclotron resonance discharges of HBr/H2/Ar and HI/H2/Ar were used to etch III–V semiconductors at temperatures in the range 50–250 °C. The increase in etch rates is non‐Arrhenius for both chemistries, but enhancements of up to a factor of 50 are seen, depending on the material, with rates of ∼1 μm min−1 for InP at 250 °C at 1 mTorr, −200 V dc and 250 W of microwave power. InP surfaces show a smooth‐to‐rough transition at ∼150 °C in HBr‐based discharges, with degraded anisotropy of the etched features. Both GaAs and AlGaAs are more resistant to this surface roughening, but preferential loss of As occurs at elevated temperatures. Similar results were obtained with HI‐based discharges, with loss of the group V element above ∼100 °C. The electrical properties of all three materials are affected by the etch treatments, with creation of a highly conducting surface layer on InP and hydrogen passivation of dopants occurring in GaAs and AlGaAs. The latter can be reversed by annealing at ∼400 °C.

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