A LEVEL SET APPROACH TO A UNIFIED MODEL FOR ETCHING, DEPOSITION, AND LITHOGRAPHY .3. REDEPOSITION, REEMISSION, SURFACE-DIFFUSION, AND COMPLEX SIMULATIONS

Previously, Adalsteinsson and Sethian have applied the level set formu lation to the problem of surface advancement in two and three-dimensio nal topography simulation of deposition, etching, and lithography proc esses in integrated circuit fabrication. The level set formulation is based on solving a Hamilton-Jacobi type equation for a propagating lev el set function, using techniques borrowed from hyperbolic conservatio n laws. Topological changes, corner, and cusp development, and accurat e determination of geometric properties such as curvature and normal d irection are naturally obtained in this setting. Part I presented the basic equations and algorithms for two dimensional simulations, includ ing the effects of isotropic and uni-directional deposition and etchin g, visibility, reflection, and material dependent etch/deposition rate s. Part II focused on the extension to three dimensions. This paper co mpletes the series, and add the effects of redeposition, reemission, a nd surface diffusion. This requires the solution of the transport equa tions for arbitrary geometries, and leads to simulations that contain multiple simultaneous competing effects of visibility, directional and source flux functions, complex sputter yield flux functions, wide ran ges of sticking coefficients for the reemission and redeposition funct ions, multilayered fronts and thin film layers. (C) 1997 Academic Pres s.