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

Paper SS1-TuA2
In situ Boron Doping of Si(100): Effects of Low Boron Concentration on Hydride Surface Reactions

Tuesday, November 3, 1998, 2:20 pm, Room 308

Session: Semiconductor Surface Chemistry
Presenter: B. Gong, University of Texas, Austin
Authors: B. Gong, University of Texas, Austin
D.E. Brown, University of Texas, Austin
S.K. Jo, Kyung Won University, South Korea
J.G. Ekerdt, University of Texas, Austin
Correspondent: Click to Email
Hydrogen desorption and hydride adsorption will potentially control film growth rates during in situ doping of Si(100) in chemical vapor deposition processes involving hydride gases. The reactions of hydrogen and disilane with boron-doped Si(100) have been studied with temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS) and low energy electron diffraction (LEED). Recent studies by our group have been conducted in the boron concentration range from 0.001 to 0.05 monolayer (ML) to illustrate the kinetic effects of in situ doping, which has a typical doping level of 10@super 16@-10@super 20@ cm@super -3@. With ~0.001 ML boron, TPD and HREELS show essentially no dihydride formation on the boron doped surface. After H-passivation, the boron doped surface (@theta@@sub B@~0.001 ML) shows a 2x1 reconstruction by LEED, while the H induced reconstruction on a clean surface at the same conditions shows a 3x1 reconstruction. This inability of the H-passivated Si(100) to undergo the 3x1 reconstruction is associated with the subsurface boron-induced silicon dimer vacancy defects. At slightly higher @theta@@sub B@, monohydride starts to be suppressed and decreases with increasing @theta@@sub B@. At @theta@@sub B@= 0.01 ML, monohydride formation decreased 15% and then more slowly with increasing boron coverage due to islanding. A boron electronic effect that deactivates silicon dangling bonds reduces active sites on the surface, which in turn shows less monohydride adsorption with increasing @theta@@sub B@. The saturation coverage of disilane decreases with increasing @theta@@sub B@ due to less dangling bonds as a result of the boron deactivating effect. However, the disilane adsorption rate increases with @theta@@sub B@ while the hydrogen desorption rate is not affected by the addition of boron. We propose that the boron effects on silicon deposition rate is a result of enhanced disilane adsorption rather than enhanced hydrogen desorption.