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Two methods are presented for simulating the development of photolithographic profiles during the resist dissolution phase. These algorithms are the volume-of-fluid algorithm, and the steady level-set algorithm. These methods are compared with the ray-trace, cell and level- set techniques employed in SAMPLE-3D. The volume-of-fluid algorithm employs an Euclidean Grid with volume fractions. At each time step, the surface is reconstructed by computing an approximation of the tangent plane of the surface in each cell that contains a value between 0 and 1. The geometry constructed in this manner is used to determine flow velocity vectors and the flux across each edge. The material is then advanced by a split advection scheme. The steady level set algorithm is an extension of the iterative level set algorithm. The steady level set algorithm combines fast level set concepts and a technique for finding zero residual solutions to the eikonal function. The etch time for each cell is calculated in a time ordered manner. Use of heap sorting data structures allows the algorithm to execute extremely quickly. A similar technique was submitted by J. Sethian. Comparisons of the methods have been performed and the results are shown.
Helmsen et al. (Fri,) studied this question.