CAD tool for modelling VLSI designs

The application of AutoCAD for VLSI design of semiconductor devices has been presented in this paper. Two approaches namely symbolic design and polygon representation have been used to develop the CAD tool for modelling of VLSI designs. Sticks represent the structure in the symbolic design. The stick design approach reduces the design efforts significantly, while maintaining the high flexibility. It is seen that without going into the details of fabrication technology and the circuit behaviour, one can be benefitted from using stick representation. This representation acts as an efficient link between circuit diagram and layout. The transformation from stick diagram to mask layout is almost one to one. The polygon representation uses rectangle as its main entity in all the layers. The approach used here was to use the LISP interpreter of AutoCAD to interface LISP routines from outside to the main AutoCAD system. This approach can be used for generating the mask patterns of complex circuits in a very simplified manner. The main advantage of this package is that it can be used on PCs very efficiently. The software is very useful considering the cost, ease of availability and ease of use. It can be used effectively for applications in semiconductor thin film devices.