Michaelis–Menten kinetics during dry etching processes

by Rimantas Knizikevičius

The chemical etching of germanium in Br₂ environment at elevated temperatures is described by the Michaelis–Menten equation. The validity limit of Michaelis–Menten kinetics is subjected to the detailed analysis. The steady-state etching rate requires synergy of two different process parameters. High purity gas should be directed to the substrate on which intermediate reaction product does not accumulate. Theoretical calculations indicate that maximum etching rate is maintained when 99.89% of the germanium surface is covered by the reaction product, and 99.9999967% of the incident Br₂ molecules are reflected from the substrate surface. Under these conditions, single GeBr₂ molecule is formed after 30 million collisions of Br₂ molecules with the germanium surface.