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

Paper SS-MoP23
Atomic Hydrogen Reactions with Si(100) Surfaces

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

Session: Surface Science Division Poster Session
Presenter: S.K. Jo, Kyung Won University, South Korea
Authors: S.K. Jo, Kyung Won University, South Korea
J.H. Kang, Kyung Won University, South Korea
B. Gong, University of Texas, Austin
D.E. Brown, University of Texas, Austin
J.M. White, University of Texas, Austin
J.G. Ekerdt, University of Texas, Austin
Correspondent: Click to Email
Chemical reactions of hydrogen atoms with Si(100)2x1 have been investigated over a wide range of substrate temperatures (T@sub s@ = 110 - 635 K) by using temperature-programmed desorption (TPD) and low-energy electron diffraction (LEED) techniques. Thermal-energy hydrogen atoms generated from a hot tungsten filament were found to react with Si(100) surfaces over the entire temperature regime, resulting in silicon etching, amorphization, and hydrogen penetration into the crystalline substrate. Extensive silicon etching occurred at all substrate temperatures investigated. A large hydrogen uptake of more than 4 monolayers (1 ML = 6.8 x 10@super 14@ H atoms/cm@super 2@) and destruction of 2x1 LEED patterns upon H exposure at T@sub s@ = 415 K and 635 K indicate that the etching continues at substrate temperatures where tri- and di-hydride species are not stable. Moreover, in addition to the H@sub 2@ desorption peak at T@sub s@ = 780 K, a new desorption peak at T@sub s@ = 850 K grew in with increasing hydrogen exposure for T@sub s@ @>=@ 415 K. Deuterium exchange experiments suggest that the 850-K peak is due to H@sub 2@ evolution from the crystalline silicon bulk. At T@sub s@ @<=@ 300 K, amorphization as well as etching of Si(100) occurred readily. The observed opposing T@sub s@ effects on the rates of hydrogenation [Si(s) + xH(g) -> SiH@sub x@(a)] and etching [SiH@sub x@(a) + (4-x)H(g) -> SiH@sub 4@(g)] reactions have been elucidated. Terrace etching and step etching have been invoked to explain the observed etching at low (@<=@ 415 K) and high (@>=@ 635 K) substrate temperatures, respectively. Implications for damage-free, dry etching of crystalline silicon surfaces by thermal-energy hydrogen atom beams are discussed.