Structured Design Methods for Digital VLSI

Beginning in the late 1970's, representatives from universities and industry convened a series of workshops on Very Large Scale Integrated Circuits (VLSI) in order to bridge the gap between abstract design and physical fabrication. Until that time, translation from the abstract logic circuit to a manufacturable layout was a labor-intensive process. Designing the physical layout required expertise in the fabrication process. Due to the laborious translation, logic designers received little feedback on the cost and performance consequences of their design decisions.

The series of VLSI workshops promoted the use of a fabrication-independent, geometric representation called CIF (Caltech Intermediate Form). Designers could produce CIF representations of their logic designs and apply simple geometrically-oriented design rules. If the CIF description met all the geometrical design rules, the design was guaranteed to be manufacturable. A number of silicon foundries would accept CIF inputs and produce fabricated chips. The CIF description would be translated automatically into detailed fabrication instructions meeting all constraints of the foundry's fabrication process.

Several benefits derived from the development of CIF and the associated design methodology it enabled:

• A standard interchange format between designers and fabricators enabled numerous Computer-Aided Design (CAD) tools to be generated and distributed. These tools helped fuel the commercial CAD tool industry.
• Universities could teach process-independent VLSI design to graduate and undergraduate students, providing students with feedback on the results of their design decisions.
• Foundry services were developed which could translate CIF files into working silicon.
• Both students and industrial chip designers could use the foundries to produce working integrated circuits on "the first silicon".

Structured Design Methods for Mechanical Systems

An NSF-sponsored workshop was held on May 2-4, 1994 entitled New Paradigms for Manufacturing NSF:94 to determine if it was feasible to define an equivalent design methodology for mechanical systems (or some subset of mechanical systems), decoupling the design representation from the fabrication process. The participants in the workshop concluded that there were enough potential similarities between the VLSI design and some classes of mechanical design for rapid prototyping to warrant further investigation. In particular, two new classes of layered manufacturing processes were identified as having strong similarities with VLSI fabrication: micro-electronic mechanical systems (MEMS) and solid freeform fabrication (SFF). MEMS employs many of the same manufacturing steps as VLSI and the MEMS community seems especially amenable to examining the VLSI design methodology to adapt it to their tasks. This workshop explored the potential for a unified design methodology aimed at supporting the MEMS fabrication technologies.
(A previous NSF sponsored workshop held on June 2-5, 1995 at Carnegie Mellon University investigated the issues of design methodologies for SFF. NSF:95)