AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS-MoP

Paper SS-MoP22
The Interactions of XeF@sub 2@ and F@sub 2@ with Si(100)

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: M.R. Tate, Massachusetts Institute of Technology
Authors: M.R. Tate, Massachusetts Institute of Technology
M.F. Bertino, Massachusetts Institute of Technology
S.C. Eckman, Massachusetts Institute of Technology
J.R. Holt, Massachusetts Institute of Technology
S.T. Ceyer, Massachusetts Institute of Technology
Correspondent: Click to Email
The interactions of molecular fluorine (F@sub 2@) and xenon difluoride (XeF@sub 2@) with Si(100) are model semiconductor etching systems. Despite the similar energetics and chemical nature of these two etchant molecules, XeF@sub 2@ is a much better etchant of Si than F@sub 2@. This comparative study probes the dynamics of the interactions of these two gas-surface systems and seeks to understand the molecular origins of this disparity in reactivity. Using gas-surface scattering techniques, three reaction channels are identified for both etchants including a novel gas-surface mechanism, atom abstraction, in which the surface abstracts a fluorine atom from the incident molecule and ejects the remaining particle into the gas phase. The fluorinated silicon surfaces resulting from exposure to F@sub 2@ and XeF@sub 2@ are nearly indistinguishable until the silicon dangling bonds are saturated - that is, only a small fraction of Si-Si lattice bonds are broken until the fluorination of the dangling bonds is complete. Beyond one monolayer of fluorine, however, only XeF@sub 2@ is able to attack the Si-Si lattice bonds, and SiF@sub 4@, an etch product, is observed to desorb. A detailed analysis of the energetics of the scattered products yields insight into the disparate reactivities of F@sub 2@ and XeF@sub 2@ with Si.