Yield Simulation for Integrated Circuits

In the summer of 1981 I was asked to consider the possibility of manufacturing a 600,000 transistor microprocessor in 1985. It was clear that the technology would only be capable of manufacturing 100,000—200,000 transistor chips with acceptable yields. The control store ROM occupied approximately half of the chip area, so I considered adding spare rows and columns to increase ROM yield. Laser—programmed polysilicon fuses would be used to switch between good and bad circuits. Since only half...