A SIMPLE-MODEL OF THE CHEMICALLY ASSISTED ION-BEAM ETCHING YIELD OF GAAS WITH CL2 AT MEDIUM CURRENT DENSITIES

We present a simple analysis of the chemically assisted ion beam etching (CAIBE) yield of a solid under exposure to an ion beam and flux of molecular chlorine, using a mass-balance approach. In this model, dichloride species formed by the dissociative chemisorption of physisorbed chlorine are removed by collisional cascade mechanisms. We show that the energy and ion flux dependences of the yield deviate from expected forms depending primarily on the surface chemisorption rate and the surface flux ratio, but even in this simple model there are reasons why the latter might not be a good parameter for the comparison of experimental data. The model describes the important features of the etch rates of GaAs in chlorine and low-energy (500-1250 eV, 0.05-0.35 mA/cm2) Ar(+), including a changing energy dependence of the yield with chlorine partial pressure.