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

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); 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