TCAD simulators need to know many properties of the materials they deal with. Conventionally, this information is stored internally in each simulator, thus being a constant source of inconsistency. For example, manipulating a material property locally in the input deck of a certain process simulator does not change this value for previous or subsequent simulators, causing a questionable result. The MAT (Material Server) tries to overcome this fact by providing a centralized facility for retrieving properties of all materials possibly occurring in TCAD applications.
Figure 7.17: The material classification tree used by the
MAT library
The MAT library stores materials and their properties on PIF as a tree structure of attributes. It uses the PAI library for reading and writing materials held in a global PBF which is accessed in parallel by applications using the MAT functions.
Materials are classified in a hierarchical tree structure internally in the MAT library, which is shown in Fig. 7.17. Properties not present for a specific material are inherited from the respective parent in the classification tree upon property queries. Name aliases are provided, so the material Silicon can be accessed with Si as well. New materials or modified properties can be introduced through subclassing from an already existing material. Thus the problem of locally modified material properties mentioned above can be overcome by subclassing a new material with a different property, and setting the respective segment material of the PIF geometry to this new material. Then all simulators working with this PIF geometry will use a consistent set of material properties for this new material.