Hydrogen in amorphous and microcrystalline silicon films prepared by hydrogen dilution

Hydrogen incorporation in silicon layers prepared by plasma-enhanced chemical-vapor deposition using silane dilution by hydrogen has been studied by infrared spectroscopy ~IR! and elastic recoil detection analysis ~ERDA!. The large range of silane dilution investigated can be divided into an amorphous and a microcrystalline zone. These two zones are separated by a narrow transition zone at a dilution level of 7.5%; here, the structure of the material cannot be clearly identified. The films in/near the amorphous/microcrystalline transition zone show a considerably enhanced hydrogen incorporation. Moreover, comparison of IR and ERDA and film stress measurements suggests that these layers contain a substantial amount of molecular hydrogen probably trapped in microvoids. In this particular case the determination of the total H content by IR spectroscopy leads to substantial errors. At silane concentrations below 6%, the hydrogen content decreases sharply and the material becomes progressively microcrystalline. The features observed in the IR-absorption modes can be clearly assigned to monoand/or dihydride bonds on ~100! and ~111! surfaces in silicon crystallites. The measurements presented here constitute a further indication for the validity of the proportionality constant of Shanks et al. @Phys. Status Solidi B 110, 43 ~1980!#, generally used to estimate the hydrogen content in ‘‘conventional’’ amorphous silicon films from IR spectroscopy; Published in Journal of Applied Physics 80, issue 9, 4971-4975, 1996 which should be used for any reference to this work 1