Comparative time-resolved study of the XeF2 etching of Mo and Si

Abstract

In situ and time-resolved infrared absorption spectroscopic measurements reveal that, under typical processing conditions (∼300 K, approximately Torr pressures), XeF2 reacts efficiently but very differently with Mo and Si substrates. This kinetic study of the surface etching processes, based on the time evolution of both reactants and products, demonstrates that the mechanisms for Mo and Si etching are different. While XeF2 produces substantial roughening and a thick fluorosilyl layer on the crystalline Si surface (>200 nm), it only reacts with the surface atoms of amorphous Mo with substantially slower kinetics. The measured kinetics are quantified by simulation and the final profile experimentally obtained on etched Si surface is shown to be consistent with a recent theoretical study of the characteristic diffusion-controlled etching of silicon.