The impact of thin film interference effects on sub-micron lithography processing

An improved method of evaluating the impact of thin film interference effects on lithographic processing is demonstrated, using oxide thickness variations. Using this method, the effect of developer contrast on three different responses to the interference (CD, time to clear and dose to clear) is investigated, and these are shown not to be equivalent: CD variations are shown to be independent of, while time to clear variations increase with, developer concentration. Dose to clear variations depend critically on the develop time criterion chosen. Simulation results are presented which aid in our understanding of these phenomena.