Laser Photochemical Growth of Amorphous Silicon at Low Temperatures and Comparison with Thermal Chemical Vapor Deposition

Abstract

ABSTRACTPulsed ArF (193 nm) excimer laser radiation has been used to dissociate disilane (Si2H6), resulting in photochemically controlled deposition of amorphous Si thin films. A high stability HeNe (6328 Å) laser was used for precise in situ monitoring of film deposition rates, under varying deposition conditions. A helium window purge nearly eliminated Si film deposition on the chamber windows. With the excimer laser beam parallel to the substrate, deposition of amorphous Si can be controlled entirely by the photon fluence (negligible background thermal growth) at temperatures from room temperature up to ~400°C. Reasonable photolytic deposition rates (>1 A/sec) are combined with "digital" control of film thickness (>0.02 A/laser pulse). Activation energies of 1.50 (±0.1) eV and 0.09 (±0.02) eV were found for pyrolytic and photolytic deposition, respectively.