Recent advances in the application of photo-lithographic techniques to semiconductor devices and microminiaturization

Liberal use has been made cf photo-lithographic and photoengraving techniques for the fabrication of semiconductor devices. The techniques have been extended to the microminiaturization of electronic assemblies. Extremely accurate control of pattern geometry can be achieved by the use of these techniques. Germanium devices fabricated at the Diamond Ordnance Fuze Laboratories include diodes, transistors, lateral photo-voltage diodes and variable capacitance diodes. The semiconductor device is mounted on a thin ceramic wafer which may be individually packaged, or the device may be incorporated as an integral part of a ceramic printed-circuit assembly. An extension of the photo-lithographic techniques permits the `printing¿ of leads by the evaporation and deposition of metals such as aluminium or gold. The outside casings of conventional resistors, capacitors, diodes and transistors are discarded and the individual components are mounted as an integral assembly on a two-dimensional ceramic printed-circuit wafer. Binary counter and `nor¿-type circuits have been built on ceramic wafers ranging in size from 0.5 in square by 0.02 in thick for the binary divider to 0.25 in square and 0.02 in thick for the `nor¿ circuit. The binary counter has two transistors, two diodes, two capacitors and eight resistors. The `nor¿ circuit has one transistor and four resistors. Component densities of 2.5 × 106 components per cubic foot have been achieved. The fabrication of typical transistors and diodes by the photolithographic process, their incorporation in circuits and future possibilities will be discussed.