A vacuum compatible lithography technique has recently been demonstrated, whereby amorphous hydrogenated silicon (a-Si:H) films are used as a resist. Following plasma deposition of the a-Si:H film, poly-Si patterns are generated on the surface by excimer laser exposure through a projection mask. Development is then carried out by hydrogen plasma etching for which etch. selectivities of over 1000:1 have been achieved between a-Si:H and poly-Si regions. However, the roughness induced by excimer laser irradiation can be well over ten times that of the as-deposited a-Si:H surface. This is problematic because the roughness may be transfer-red to underlying device layers during subsequent pattern transfer plasma etching. We have developed a stepwise laser irradiation procedure that reduces the surface roughness by an order of magnitude to a level of similar to 1 nm. This value is approximately equal to the surface roughness for the as-deposited a-Si:H film. The irradiation procedure uses multiple pulses with progressive increases in the energy density, in contrast to the single high energy density pulses previously used. Transmission electron microscopy and Fourier transform infrared spectroscopy are used to understand and confirm the mechanism behind this process. Our data suggest that the observed reduction in roughness is due both to smaller grain sizes and to a slow rate of H removal from the film surface. The results may also hold significance for other applications of laser processed a-Si:H, even where different film properties are desired. (c) 2006 American Vacuum Society.