2.1 Requirements for a TCAD Data Model

The four major aspects that need to be dealt with in a TCAD simulation from the tool's perspective are

• Persistent storage of simulation data. The tool must store the results of a simulation for later reference (visualization, input for another simulation) and the user does not want to bother with file format specifics.

• Handling of gridding steps. The tool needs a standardized way to interact with different gridding tools. It must be possible to switch to another gridding algorithm with the least possible effort.

• The user needs support to extract topological information, in order to manipulate the underlying geometry after a topography step.

• All data structures and algorithms offered by the data model should be available in three spatial dimensions.

The observed semantical incompatibilities in existing solutions are often due to oversimplifications. On the one hand such simplifications can help in managing the data for one kind of simulator but complicate the generation of a valid Wafer on the other. One such simplification is to enforce boundary conforming grids on the data stored on a file as it is the case with the DF-ISE approach. Another (design related) simplification is the lack of so-called WAFER-STATE semantics. A WAFER-STATE defines a state after any simulation run that is carried out in the simulation of a process flow. It is this definition that is most important to a tool, and yet, no standard has evolved so far.

In the following we will focus on the data structures and the API that were developed to support the tool developer with the desired operations. All above defined requirements are met and reflected in the API. The API and data structures are referred to under the term WAFER-STATE-SERVER. Note that in our application the term "SERVER" does not denote a traditional client/server architecture as it is used in e.g. web-based applications, but is rather meant to denote the set of classes that comprise and enforce the WAFER-STATE definition.

2003-03-27