One aspect of the invention relates to a method of removing contaminants from a low-k film. The method involves forming a sacrificial layer over the contaminated film. The contaminants combine with the sacrificial layer and are removed by etching away the sacrificial layer. An effective material for the sacrificial layer is, for example, a silicon carbide. The method can be used to prevent the occurrence of pattern defects in chemically amplified photoresists formed over low-k films.