Mechanisms of low temperature epitaxial silicon growth using ArF excimer laser photochemical vapor deposition from disilane

Abstract An ArF excimer laser has been used with the beam parallel to the Si(100) substrate in order to deposit homoepitaxial silicon films at temperatures from 250 to 350 °C with growth rates from 1 to 10 A min −1 . The growth involves photolytic decomposition of Si 2 H 6 and the generation and adsorption of growth precursors on the hydrogenated silicon surface. The deposition yield of solid silicon from photo-excited Si 2 H 6 is estimated to be 0.20 ± 0.04. Growth rates vary linearly with laser intensity and Si 2 H 6 partial pressure over the ranges 1–15 mJ cm − pulse −1 and 5–40 m Torr respectively. Epitaxy is maintained for temperatures above the threshold for thermal dissociation of surface (SiH 2 ) n chains at about 250 °C, and for temperatures below the onset of Si 2 H 6 pyrolysis and rapid thermal desorption of surface H 2 at about 350 °C. Epitaxy is achieved for laser intensities and Si 2 H 6 partial pressures that result in low initial photofragment concentrations (below 10 13 cm −3 ), and for total pressure and flow conditions such that there is little secondary photolysis of the initial photofragments. Very low defect density films in terms of stacking faults and dislocation loops (less than 10 5 cm −2 ), and excellent crystallinity, have been grown, as confirmed by Schimmel defect etching in conjunction with Nomarski microscopy, transmission electron microscopy, electron diffraction and in situ reflection high energy electron diffraction.