FIRST-PRINCIPLES STUDY OF CHLORINE ADSORPTION AND REACTIONS ON SI(100)

First-principles local-density-functional calculations on the interact ion of chlorine with the Si(100)-2x1 surface are presented. Cl-2 adsor ption and a number of reactions relevant to etching via desorption of SiCl2 species are considered, both at the defect-free surface, and in the presence of small surface defects. The formation of SiCl2 species via an isomerization-mechanism, their stabilization and desorption are studied. Whereas this is a likely route towards spontaneous etching o f the surface in the limit of low Cl coverage (theta(Cl)), at theta(Cl )similar to 1 it is energetically very costly. In the high coverage li mit the formation of SiCl2 by either a Cl atom reacting with a monochl oride surface species or by dissociative chemisorption of hyperthermal Cl-2 molecules is investigated. For the latter, a barrier for dimer-b ond breaking of 0.5-1 eV is estimated. Our results show that both the Cl-2 adsorption energy and the SiCl2 desorption energy decrease signif icantly with increasing the local chlorine concentration above one mon olayer. [S0163-1829(98)08015-1].