Temperature Dependence of InP and GaAs Etching in a Chlorine Plasma

InP and GaAs etching in chlorine plasmas at 0.3 Torr follows an Arrhenius dependence on substrate temperature. Apparent activation energies, E a , of 34.5 ± 2.8 and 10.5 ± 0.7 kcal / mol , respectively, were determined from both optical emission of product species, and step height or weight change measurements. For InP , E a equals the heat of vaporization of InCl 3 ( s ) , and the absolute etch rate (7 μm/min at 250°C) is in reasonable agreement with the predicted vaporization rate of InCl 3 . Hence, volatilization of InCl 3 ( s ) is most likely the rate‐controlling step for etching InP . Sputter Auger analysis shows that etching in a chlorine plasma leaves multiple layer coverage of InCl 3 on InP (removable by washing with deionized water), and submonolayer levels of chlorine on GaAs . Both surfaces are rich in the group III element. The etched surface morphologies of InP and GaAs are strongly dependent on temperature, exhibiting a rough‐to‐smooth texture transition above ∼250° and ∼120°C, respectively.