13.1 Methods for Describing Moving Boundaries

Describing the wafer surface and its change due to the fluxes of etchants and particles to be deposited is a vital part of topography simulations, which were outlined in Section 12.2. The problem of topography simulation can generally be divided into two parts. First a suitable representation of surfaces including a discretization must be found. It represents the parts (and boundaries) of the simulation domain consisting of silicon, silicon dioxide, silicon nitride, etc. Second, and most importantly, operations on this representation must be defined and implemented that allow to track the movement of the boundaries in an efficient, robust, and precise manner. These operations are the growth, the removal, and the joining of boundaries. As we will see in the following section, different approaches to this problem have been devised and research to improve methods for surface description is still being conducted.