Effects of Ar+ angle of incidence on the etching of Si with Cl2 and low-energy Ar+ ions

Abstract

Experiments have been performed in a beam apparatus where an Ar+ beam and a Cl2 beam are directed simultaneously at a Si target. The apparatus allows independent variation of the ion angle-of-incidence and the detection angle. Time-of-flight (TOF) distributions of the reaction product SiCl are measured for various Cl2 to Ar+ flux ratios and various angles-of-incidence. These distributions can for the larger part well be fitted with collision cascade distributions, showing that at the parameter values chosen, the etch process in Si(Cl2,Ar+) is a chemically enhanced physical sputtering process. The observed variations of the binding energy U0 obtained from the TOF distributions support this mechanism. A discussion in relation to similar studies on the etch rate and the composition of the surface and the altered layer leads to a consistent picture in support of the above model.