Contribution and control of neutral gas absorption effects in the plasma doping of boron into Si

In the low energy plasma doping process, the contribution of not only ionized species but also neutral species to the doping process should be considered. In order to investigate such a contribution, the experiments of gas phase doping combined with Ar or He plasma pre-treatment were carried out. Gas phase impurity absorption should be affected by surface condition of Si substrates. As a result, significant increase of boron dose from neutral gas phase was observed when the substrate surface was pre-treated by Ar or He plasma prior to exposure to neutral B₂H₆/He gas. It was also found that the gas phase impurity absorption was affected by substrate temperature when the surface was exposed to the neutral B₂H₆/He gas.