A general numerical procedure for multilayer multistep IC process simulation

A new numerical procedure is presented for the simulation of multistep processes in IC fabrication of nonplanar multilayered structures. The numerical scheme utilizes a multizone adaptive grid generation (MAGG) technique for the discretization of the physical domains of arbitrary shape that may involve free or moving boundaries. The process model equations are discretized in the physical space using a curvilinear finite-volume formulation. The numerical scheme is validated by simulating silicon oxidation process (with the inclusion of stress effects) on a 50° trench and comparing the results with the published SEM photographic data. Capabilities of the methodology, including geometric flexibility, efficiency in grid distribution, accuracy in treating the moving boundaries, and facility for modification of the physical model are discussed. These characteristics are demonstrated by simulating simultaneous silicon oxidation and impurity diffusion in trench structures with corner angles equal to, and greater than, 90°