Multiple exposure with image reversal in a single photoresist layer

Abstract

Multiple patterned exposures of a single layer of image reversal resist prior to and following image reversal processing, upon development, respond to the respective exposures as either a positive or a negative resist, allowing a desired shape of a resist structure to be built up from any of a number of combinations of primitive masks. Exploiting the image reversal resist in this manner allows several types of diffraction distortion to be entirely avoided and for many sophisticated lithographic processes to he reduced in complexity by one-half or more while any desired resist structure shape can be formed form a limited number of primitive mask patterns. A regimen, which may be automated as an executable algorithm for a computer may be followed to evaluate different combinations of masks which are valid to produce a desired resist structure shape and select the optimum mask pattern combination to do so.