Three-dimensional simulation of optical lithography

A 3-D optical lithography simulator has been developed based on a new ray-string algorithm for dissolution etch-front advancement. This simulator, SAMPLE-3D, integrates a number of process simulators on a workstation while also providing display and print capabilities. SAMPLE-3D has been used to look at 3D resist profiles from 2-dimensional mask patterns, including isolated contacts, isolated islands, and elbow patterns. Simulations have been performed on both positive and negative photoresists, and the effects of resist contrast and surface rate retardation were explored. The correlation between the 2D aerial image and the 3D developed resist profile has been investigated. This includes applications to the printability of defects where the nonvertical resist dissolution effects play a strong role.