A discretionary wiring system as the interface between design automation and semiconductor array manufacture

The trend toward computer-aided design, with its resulting increased complexity and specialized circuitry, places particular emphasis on methods of translating design ideas into hardware. In present integrated circuit structures this is accomplished by an iterative process involving both materials pcocessing and geometrical variations. Because of the large number of similar devices being processed, this "trial and error" method can be tolerated, but the full utilization of design automation methods for custom applications is only possible if functional operation can be assured with a number of units. This means that circuit variation must be introduced into the manufacturing process through the photolithographic masking process while maintaining an invariant materials process. In this article, the design automation and fabrication sequence of LSI arrays is reviewed, with particular emphasis on the photomasking requirements. Unique, computer controlled equipment for the rapid generation of masks from a cathode-ray tube is described. An illustration is given of the actual information flow that takes place when this equipment is used to discretionarily interconnect an LSI array.