Deposition of amorphous hydrogenated silicon films (a‐Si:H) on a glass substrate by photodissociation of SiH4using a focused ArF excimer laser beam directed parallel to the substrate has been demonstrated. The rate of film deposition increased with irradiation time at constant laser power, with a fixed initial quantity of reactant gas. This result indicates the formation of Si2H6, which is excited by a single incident photon. The small amount of Si2H6formed promoted photodecomposition of SiH4.