Proposal of quasi thermal equilibrium model for etching phenomenon by gases: Example of the etching of 4H-SiC by H2

Abstract

We propose a new approach to derive the formula for the etching rate of condensed matter with a gaseous etchant, based on the model in which the chemical etching proceeds under nearly thermal equilibrium conditions. The model, called the quasi thermal equilibrium model, is applicable for the case that the reaction time is much shorter than the passage time of carrier gases over substrates. We have derived the formula giving the etching rates as functions of temperature, gas flow rate, and pressure for three cases: (1) a carrier gas acts as an etching gas, (2) a carrier gas is inactive and an etching gas is added, and (3) a carrier gas is active and an etching gas is added. We applied the model to the etching of 4H-SiC by H2 and showed that the quasi thermal equilibrium model proposed can successfully reproduce the experimental results of the temperature, gas flow rate, and pressure dependences of the etching rate.