Near-surface defects in hydrogen-plasma-treated boron-doped silicon studied by positron beam spectroscopy

Near-surface vacancy-type defects have been studied by positron beam spectroscopy in three boron-doped Si wafers; a control sample, second sample exposed to atomic hydrogen in electron cyclotron resonance (ECR) plasma, and a third sample annealed at 500°C following plasma treatment. From the analysis of the Doppler broadening spectra, measured as a function of positron implantation depth, we obtain positron diffusion lengths of about 100 and 250 nm for the damaged layer and bulk of the wafer, respectively. For the plasma-treated wafer, our measurements provide a defect density of about 5 × 10¹⁷ cm^-3.