An advanced SVG technology for 64K junction-shorting PROM´s

The memory cell size of the 64 kbit PROM was reduced to 168µm²(0.26 mil²) by using advanced SVG (Shallow V-Groove) isolation and the wafer stepper process. SVG isolation was introduced in 1979 to suppress the SCR latching between two neighboring cells in the 4 kbit junction-shorting PROM. Since then, the cell size has been reduced until it became limited by the widths of word and bit lines. In the 64 kbit PROM, the SVG isolation technology was improved to achieve self-alignment in diffusion, to provide a high breakdown voltage for Schottky diodes, and to increase the flexibility of the mask layout. The size of the peripheral circuitry was thus reduced to allow a smaller cell size and a smaller parasitic capacitance. The memory cell array occupies 45.0 percent of the total die size of 7.14 × 5.28 mm².