The 20 µm lithography process was the semiconductor process technology used by the major semiconductor companies during the years of 1963 and 1966. 20 µm was roughly the pitch between the centers of two smallest-sized transistors. The typical wafer size for this process at companies such as Fairchild was 0.875 inch (19 mm). The standard transistor packages those years were the TO-5 and TO-18 (Transistor Outline) metal-can packages.

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