Computer-Aided Layout System for Integrated Circuits

A computer-aided mask layout system is described. The purpose of the system is to assist the designer in making the transition from logic diagram or circuit schematic to camera-ready artwork. The system is used for device design, device layout, cell layout, and layout of integrated circuits up through large-scale integration (LSI). Techniques used for placement and routing include an automatic system, a CRT system, and an off-line digitizer (or card) input system. Output is from a precision photo plotter and an ink plotter. The layout system runs on a small-scale (16 thousand words) digital computer; the hardware cost of operation is relatively low. When the layout system is utilized properly, benefits are obtained in the areas of shorter design time, lower cost design, elimination of layout errors, and the capability of laying out circuits that could not be done with older techniques. Development of LSI, particularly of custom LSI, has added importance to new design procedures.