As technology evolves, new simulation capabilities are steadily required. This new methodology can either be provided by extending existing tools (which sometimes, when modularization is not possible, leads to an unhealthy growth of tools and poses a severe maintenance problem), by implementing new tools, or by integrating other existing tools which are known to solve the problem.
The time from the request for simulation capabilities to their actual availability is comprised by several time factors, each corresponding to a phase of a typical TCAD tool development process.
Although physical modeling is the most intriguing and highest regarded task, it may be doubted that this is also the major cause of the permanent delay of simulation capabilities. Furthermore, except for physical modeling and calibration, all these factors are significantly dominated by software problems of rather generic nature and are not specific to Technology CAD. The very same software problems limit the amount of re-use of TCAD software and are a burden which hamper the work of both end users and TCAD software support groups.
From a tool developer's and tool integrator's point of view, the prevailing software engineering situation in Technology CAD is very close to the following worst case.
A typical proven TCAD simulation tool consists of 1 to 3 MB poorly documented, little modular source code. Much time is spent on acquiring otherwise inadequately represented knowledge from the application's source code instead of effectively re-using the already spent engineering work.