Classical interatomic potential model for Si/H/Br systems and its application to atomistic Si etching simulation by HBr(+)

Abstract

An interatomic potential model for Si/H/Br systems has been developed for performing classical molecular dynamics simulations of Si etching processes by HBr plasmas. The potential form used here is the improved Stillinger–Weber potential function involving a correction term in order to predict the reaction dynamics more accurately. Parameters were determined based on ab initio data obtained from previous works on Si/Br systems by [Ohta et al.J. Appl. Phys.104, 073302 (2008)]. By using this model, we performed Si etching simulations by monoenergetic HBr(+) and Br(+) beams. H atom has about 1% of the translational energy of cluster ions due to the small H/Br mass ratio (=1.0/79.9)(=1.0/79.9); therefore, H atoms in HBr(+) behave like H radicals. This results in higher etch yields by HBr(+) than those by Br(+) in the low-energy region (less than 100 eV). This can be attributed to the chemical enhancement induced by the formation of Si–H bonds. On the other hand, yields by HBr(+) and Br(+) were almost the same in the high-energy region (more than 100 eV), where physical sputtering was relatively dominant and the contribution of H was small.