SiCl4 desorption in chlorine etching of Si(100) - a first principles study

Citation
Sp. Chan et al., SiCl4 desorption in chlorine etching of Si(100) - a first principles study, SURF SCI, 432(1-2), 1999, pp. 125-138
Citations number
41
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
SURFACE SCIENCE
ISSN journal
0039-6028 → ACNP
Volume
432
Issue
1-2
Year of publication
1999
Pages
125 - 138
Database
ISI
SICI code
0039-6028(19990709)432:1-2<125:SDICEO>2.0.ZU;2-F
Abstract
The formation and desorption mechanisms of SiCl4 on Si(100), which are some of the main reaction pathways in etching silicon with chlorine, have been studied with first-principle calculations. Starting from the Si(100)-(2 x 1 ) surface with 1 ML (monolayer) of chlorine to saturate the dangling bonds of Si-Si dimers, further addition of chlorine atoms leads to the breaking o f the dimer bonds or back-bonds and, therefore, formation of SiCl2(ad) whic h has a high desorption energy barrier. When chlorine atoms penetrate below the first silicon layer, they couple with SiCl2(ad) to form various precur sors of SiCl4(ad). The calculations have identified three physisorbed SiCl4 (ad) species, and four chemisorbed SiCl4(ad) species. The formation and des orption barriers of these species are lower than that of SiCl2(ad). Hence, at low temperatures, SiCl2 desorption is barred by its high desorption ener gy, which makes the formation and desorption of SiCl4 more favorable, At hi gh temperatures, desorption of SiCl2 can proceed and thus reduces the proba bility of SiCl4(ad) formation. The availability of hyperthermal chlorine sp ecies or ion bombardment can promote both the formation of SiCl4(ad) and de sorption of SiCl2(ad), and thereby increases the etching rate and changes t he reaction dynamics, A mild energetic condition will favor the formation a nd desorption of SiCl4. The etching mechanism model provides a good framewo rk to explain the experimental data in the literature on etching silicon wi th thermal and hyperthermal chlorine. (C) 1999 Elsevier Science B.V. All ri ghts reserved.