AVS 45th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA1
The Effect of Phosphorus and Germanium on Silicon Surface Chemistry

Tuesday, November 3, 1998, 2:00 pm, Room 308

Session: Semiconductor Surface Chemistry
Presenter: J.E. Crowell, University of California, San Diego
Authors: J.E. Crowell, University of California, San Diego
M.L. Jacobson, University of California, San Diego
G.J. Batinica, University of California, San Diego
M.C. Chiu, University of California, San Diego
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Our studies focus on the deposition surface chemistry of Group IV semiconductors. We have examined the effect that adatoms such as P, Ge, and both P/Ge have on (i) the Si precursor chemisorption behavior and (ii) the hydrogen desorption behavior. Surface phosphorus contains a lone pair of electrons rather than a dangling bond and is thus passive to adsorbing gas molecules, and acts as a site blocker to species diffusing on the surface. In contrast, Ge adatoms contain a dangling bond and behave in a way similar to Si. However, both adatoms modify the surface chemistry of silicon. This presentation will describe TPD, AES, and MIRIRS studies aimed at determining the effect of pre-adsorbed P and Ge on the reactivity of Si(100) and Si(111) surfaces. For example, disilane (Si@sub 2@H@sub 6@) reacts with the Si(100) surface at 300K to form a mixture of SiH@sub x@ species. At higher temperatures, recombination reactions occur which produce silane (SiH@sub 4@) and H@sub 2@ that subsequently desorb. The reactivity of the Si(100) surface decreases with increasing P coverage, as determined by the increase in the selectivity of the Si@sub 2@H@sub 6@ reaction toward SiH@sub 4@ production over H@sub 2@ production. The H@sub 2@ desorption temperature increases with increasing P coverage while the SiH@sub 4@ desorption temperature decreases. A similar increase in H@sub 2@ desorption energy was seen upon H atom exposure of the P/Si surface, whereas Ge pre-adsorption decreases it. These results, a comparison of the (100) and (111) Si surfaces, and the combined effect of P and Ge will be discussed within the framework of electronic and morphological modifications of the surface and ensemble size effects caused by the presence of these pre-adsorbed adatoms.