Limits of optical lithography

This paper describes a new theoretical and experimental approach to understanding optical lithography. Optical absorption properties of positive photoresist are used in the determination of an exposure distribution within the resist. A development rate relationship is used to calculate developed image surface contours from the exposure distribution. This description of resist performance seems to apply down to the finest detail optically resolvable, the interference between two opposing coherent light beams. The major limits to achieving very high resolution lie in the difficulty of obtaining the desired exposure distribution and in the common misunderstanding that exposure should control image contours directly rather than indirectly through a development rate relationship.