Contribution of ions to the growth of amorphous, polymorphous, and microcrystalline silicon thin films

The growth of amorphous, microcrystalline, and polymorphous silicon has bee n investigated by studying the species contributing to the growth and resul ting film structure. The surface reaction probability of the radicals and t he contribution of ions to the growth have been determined. In a-Si:H depos ition by hot wire chemical vapor deposition, the surface reaction probabili ty (beta=0.29) of the depositing radical is compatible with SiH3, whereas t he surface reaction probability in microcrystalline silicon growth is highe r (0.36 less than or equal to beta less than or equal to 0.54). On the cont rary, the deposition of amorphous silicon by plasma enhanced chemical vapor deposition indicates the contribution of more reactive radicals than SiH3. The deposition of polymorphous and microcrystalline silicon by plasma is d ominated by ions, which can contribute up to 70% of the deposited film. Thi s is attributed to efficient ionization of silane in charge exchange reacti ons with hydrogen ions. The surface reaction probability in the case of pol ymorphous silicon deposition (beta approximate to 0.30) is intermediate bet ween that of a-Si:H deposition (beta approximate to 0.40) and that of micro crystalline silicon deposition (beta approximate to 0.20). Etching of amorp hous silicon by means of a hydrogen plasma shows that ions may hinder the p rocess. (C) 2000 American Institute of Physics. [S0021-8979(00)05619-X].