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

We study the dynamics of the reaction layer during Ar+ ion-assisted Si etch ing by XeF2 in the temperature range T=150-800 K. Depending on temperature, the etch rate can be enhanced a factor of 8 by ion bombardment. The dynami cs 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 coverag e and dangling bonds is found to be formed on the Si(100) surface during io n bombardment. The dangling bond concentration increases with ion flux and is independent of temperature in the range 150-600 K. Chemisorption on thes e dangling bonds results in a higher reaction probability of XeF2. The temp erature dependence of the reaction probability of XeF2 is fully determined by the temperature dependence of the XeF2 precursor state. A simple model g ives a very good description of the reaction probability as a function of b oth temperature and ion flux. The model description of the behavior of the precursor concentration as a function of ion flux and temperature is confir med by ion pulse measurements on a time scale of 1 s. Further, it is conclu ded that the mechanisms for enhanced SiF4 formation during ion bombardment are the same over the temperature range studied. (C) 2000 American Vacuum S ociety. [S0734-2101(00)04106-3].