A general simulator for VLSI lithography and etching processes: Part I—Application to projection lithography

A simulator is described which produces line-edge profiles at various key stages in integrated circuit processing. Optical models are included for contact and projection lithography. The effects of multiple wavelengths, defocus, and partially coherent sources may be simulated in projection lithography. The positive resist model of Dill is used with the string development model of Jewett to obtain resist line-edge profiles. The string model is generalized to surface reaction rate limited etching of any layer. The application of the simulator to projection lithography is illustrated with a number of examples including monochromatic and multiwavelength exposure, the effect of a post-exposure anneal, plasma descum, and defocus.