This paper discusses an extension of the fast multipole method to electromagnetic scattering from doubly periodic, multilayer wafer topography. The novelty of our approach lies in the use of a pseudo-periodic translation operator which can be computed efficiently using fast Fourier transform. Results obtained using the rigorous boundary conditions for dielectric surfaces are compared with those obtained using the approximate impedance boundary condition. The latter is shown to give good results for the type of topography usually encountered in lithography simulation. Results of reflective-notching simulation using the IBC method are presented.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.