Pattern mask generating method and apparatus

Abstract

High-density multilayered integrated circuits are fabricated by first generating all photomasks for the respective layers concurrently during the same exposure operation. Since ambient conditions are identical during generation of these related masks, mask-to-mask misregistration is virtually eliminated. While photosensitive substrates are supported on a rotating turntable, a laser beam is incremented radially toward the turntable axis and modulated to expose selected portions of each of a series of contiguous concentric bands on each substrate sequentially. Thus, in generating a four-layered circuit, the four different photomasks for the respective layers would be generated by selective exposure of each mask in sequence within the same concentric band; then, after the beam is incremented radially, each mask would again be selectively exposed in sequence within a contiguous concentric band, etc. Alternatively, the laser beam is replaced by an electron beam; and a deflection yoke electrostatically deflects the electron beam to provide a series of chord-like contiguous scans as each substrate passes through the beam path. This provides rectilinear patterns on the masks without need for the programming necessary with a laser beam to convert X-Y coordinate data into polar coordinate data. The turntable is dynamically balanced in a unique manner; and clocking is precision monitored to enable precise registration of the masks capable, when photoreduced, to provide patterns with image elements as fine as five microinches.