Simulation of exposure process in complex nonplanar 2D/3D resist-substrate structures

Predictive and efficient lithography simulation is an important component of the semiconductor industry efforts to develop the next generation of deep submicron technologies. Emerging technologies are based on elements with very small feature sizes and extremely complex and nonplanar topographies. Therefore lithography processing has to provide high resolution with large depth of focus. Simultaneously such effects as nonplanar reflections and notching as well as refractive index dependence on local absorbed dose are very critical for printing small mask elements using short wavelength radiation. This work presents a new approach for simulating the exposure process that takes into account these effects in complex nonplanar 2D/3D resist-substrate structures. Because the method is very general it can be used for different types of radiation (UV, EUV, X-ray) as well as for multiexposure processes and multilayer and nonlinear resists. Complete exposure simulations for a typical 2D structure take 2-20 sec on a Sun Ultra-10 workstation while 3D simulations may take from 0.5 to 30 minutes.