2.3.1 Human Aspects of TCAD Methodology

Methodology has two important facets, these are the application of methodology and the development of methodology. Technology CAD, as a methodology, also exhibits these two entirely different facets. TCAD is applied to solve device and process design problems and new or improved TCAD functionality is continuously created to accommodate changing application requirements. So if one, with all due right, complains the permanent lag of TCAD capabilities with respect to the status of technology, the search for the causes of this lag must include a thorough examination of the dynamic methodology creation process.  

It has already been mentioned that the evolution of TCAD started with single applications (point tools) that were designed and implemented independently by different tool developers. A developer (sometimes a small team of developers) has taken care for a single application, which has traditionally been developed with an emphasis on a specific TCAD application problem, usually without consideration of the (software) environment in which the application will be used.

  
Figure 2.3: Early integrated TCAD

The views of TCAD methodology of tool developer and user are different. Developers have detailed, in-depth knowledge of a single tool, or of part of a single tool, whereas users have shallow, essential, problem-oriented knowledge of all tools used. This is also valid when tools, for the advantage of users, are combined by tool integrators into integrated TCAD systems (see Figure 2.3).

L.KLEINFELDT et al. [2] identify the following categories of users for the ECAD area.

• ``Designers - The ultimate end-users, people who execute CAD tools in a formal or informal design methodology.
• Tool Developers - People who write new CAD tools for use by designers.
• Tool Integrators - People who combine tools and hide dependencies among tools. They also customize vendor tools to a specific site's needs.
• Methodology Developers - Chief designer gurus who describe the design methodology to be used.
• Managers - Those who supervise all of the above.''

Note that in this realistic model of TCAD methodology (Figure 2.3), the constituent system components are still essentially tied together by human efforts. While this might be acceptable as long as they are one-time efforts, the maintenance of such a system is certainly a tedious and redundant work.