Reaction layer dynamics in ion-assisted Si/XeF2 etching: Temperature dependence

Abstract

We study the dynamics of the reaction layer during Ar ϩ ion-assisted Si etching by XeF 2 in the temperature range Tϭ150-800 K. Depending on temperature, the etch rate can be enhanced a factor of 8 by ion bombardment. The dynamics are studied with ion-pulse measurements on a time scale of 1-100 s in a molecular beam setup. A reaction layer with a submonolayer fluorine coverage and dangling bonds is found to be formed on the Si͑100͒ surface during ion bombardment. The dangling bond concentration increases with ion flux and is independent of temperature in the range 150-600 K. Chemisorption on these dangling bonds results in a higher reaction probability of XeF 2 . The temperature dependence of the reaction probability of XeF 2 is fully determined by the temperature dependence of the XeF 2 precursor state. A simple model gives a very good description of the reaction probability as a function of both temperature and ion flux. The model description of the behavior of the precursor concentration as a function of ion flux and temperature is confirmed by ion pulse measurements on a time scale of 1 s. Further, it is concluded that the mechanisms for enhanced SiF 4 formation during ion bombardment are the same over the temperature range studied.

Silicon Etching in XeF2Environment

“…The values of reaction rate constants and frequencies, found by extrapolation from experimental data, are presented in Table. It is observed that ion bombardment increases adsorption of XeF 2 molecules and C x H y molecules. The obtained theoretical results are in agreement with experimental measurements [24]. The removal frequencies of XeF 2 , SiF 4 molecules, and Xe atoms increase in the presence of ion bombardment.…”