Tin oxide (non-doped) films have been prepared by a photochemical vapour deposition (photo-CVD) from Tetramethyltin (TMT) (Sn(CH3)(4)) and O-2 (containing O-3) A low-pressure mercury lamp was used as the light source. The effect of the UV light irradiation on the film thickness distribution along 5 cm x 5 cm area was examined. By piling Teflon films on the surface of the suprasil window, the Light intensity of 184.9 nm UV wavelength of the low-pressure mercury lamp was controlled, while that of 253.7 nm wavelength through the Teflon hardly changed. As a result, the uniformity of the film thickness distribution was improved as the light intensity (184.9 nn) increased. The UV 184.9 nm Light irradiation may have improved the uniformity of the reactive species distribution in the vapour phase, which may result in the formation of the uniform thickness distribution.