Wafers of n-type material were exposed to a capacitively coupled radio-frequency H plasma, with power densities of between 0.01 and 0.2W/cm2 at 260C. The properties of the layers were investigated by using deep-level transient spectroscopy and capacitance-voltage methods. As well as the neutralization of Si donors by in-diffused H atoms, it was found that there was a modification of the deep-level transient spectroscopy spectra after hydrogenation. At two radio-frequency power densities of less than 0.IW/cm2, deep levels in the original material were passivated. The results also indicated that the complexes which were present were either electrically inactive or were located deep within the energy band-gap. At power densities of more than 0.1W/cm2, two new deep states appeared at 0.41 and 0.55eV below the conduction band. These levels were attributed to a large number of defects which were situated in the near-surface region of n-type Si-doped material after H plasma exposure. It was suggested that the trapping of H at these defects was probably responsible for the observed accumulation of H in the near-surface region.

A.Jalil, A.Heurtel, Y.Marfaing, J.Chevallier: Journal of Applied Physics, 1989, 66[12], 5854-61