Hydrogen plasma treatment: desorption of atomic hydrogen from silicon surfaces studied by in-situ spectroscopic ellipsometry

The use of H₂ and Ar plasmas for the cleaning of crystalline Si surfaces has been investigated previously by in-situ spectroscopic ellipsometry, LEED and Auger spectroscopy. H₂ plasma treatment, followed by annealing at 700°C to desorb the adsorbed hydrogen, was found to produce high quality clean crystalline surfaces. Ellipsometry was shown to be sensitive not only to surface oxide layers and micro-roughness but also to hydrogen adsorbed on silicon surface. The desorption of hydrogen as a function of temperature from H₂ plasma treated Si (1 0 0) and (1 1 1) surfaces was investigated. The presence of different phases of adsorbed hydrogen was shown by spectroscopic ellipsometry, in agreement with UPS and EELS studies. The clean (plasma treated and annealed) Si (1 0 0) and Si (1 1 1) surfaces show differences in their apparent dielectric functions, which may be due to the nature of the surface reconstruction.