Selective area homoepitaxial growth of InP in 50 nm scale dense features has been demonstrated using hydrogen silsesquioxane (HSQ) as the growth mask. The HSQ growth mask was patterned lithographically using high resolution interference lithography at 157 nm. Lithographic process conditions were optimized, including postapplication bake temperature, developer normality, and oxygen levels during exposure. (c) 2005 American Vacuum Society.