Technology CAD is challenged by two classes of problems. The first, more traditional challenge, is the accuracy of TCAD predictions and models for isolated manufacturing and design problems. Faster algorithms and more accurate models will allow more precise statements about the properties of the investigated design. The second, more recent challenge lies in the robust reproduction of increasingly complex manufacturing proceses. To attack this problem, several entirely different, specialized simulation tools must be combined to produce a final wafer state. Very similar to real life, difficulties arise due to the narrow focus of the specialists which operate only on well-defined problems and due their inability to find a common language. A manager is required to define problems, coordinate efforts, and to summarize the results. In the case of VISTA the role of the manager is played by the Simulation Flow Control (SFC) [86] module which decomposes the whole problem into specialist's tasks, and by VORONOI which resolves some of the conflicts arising from the focus and peculiarities of the different tools.
The latter challenge is especially prevalent in fabrication process which employ a tight interaction between structuring and doping techniques. Such a class of technologies is found among planarized and trench isolation processes. An advanced process which employs both trench isolation and planarization techniques has been presented by Wen et al. (IBM) [139].