Investigation of etching characteristics of HVPE-grown c-In2O3 layers by hydrogen-environment anisotropic thermal etching

A hydrogen-environment anisotropic thermal etching (HEATE) method, which is a top-down etching process with the advantages of high controllability, large-area adaptability, and low damage to the etched surface, was applied to c-In2O3 layer. The etching characteristics under the HEATE conditions using a H2 flow at various temperatures and various low total pressures were investigated using (1 1 1) c-In2O3 layers grown by halide vapor phase epitaxy on (0 0 0 1) sapphire substrates. The onset temperature of etching at a low pressure of 5.7 × 10−4 atm and the onset total pressure of etching at 800 °C were approximately 600 °C and 2.0 × 10−5 atm, respectively. Etching occurred without the formation of In droplets on the surfaces under the investigated conditions. The etching rate for c-In2O3 increased with increasing temperature and pressure and could be controlled with nanometer-scale order in the range from 1 to 75 nm min−1. The etching rate estimated from the thermodynamic analysis was in good agreement with the experimental results, indicating that the experimental results follow thermodynamics.