NUCLEATION BEHAVIOR IN MOLECULAR-BEAM AND CHEMICAL-VAPOR-DEPOSITION OF SILICON ON SI(111)-(7X7)

The nucleation behavior during chemical vapor deposition (CVD) of sili con on Si(111)-(7X7) using disilane (Si2H6) is investigated with a sca nning tunneling microscope. In the temperature range from 450 to 540 d egrees C it is compared to molecular beam epitaxy (MBE). Whereas the l atter is very well described within the framework of classical rate eq uation based nucleation theories in the complete condensation regime, the same approach fails for CVD growth. For MBE a critical nucleus i= 5-7 is found. Although the relationship between island density and gro wth rate in CVD also follows a power law as does MBE, the exponent is significantly higher than the theoretically expected value. The influe nce of hydrogen present on the surface during CVD growth is also discu ssed. (C) 1996 American Vacuum Society.