Micralign

The Micralign was a family of aligners introduced in 1973 by Perkin-Elmer. It was the first projection aligner and was used in semiconductor fabrication.^[1]

The Micralign addressed mask alignment in photolithography, where each layer of an integrated circuit is patterned onto a wafer through repeated exposure steps.^[1]

In photolithography, a wafer is coated with photoresist, a mask carrying one layer of the chip design is placed over it, and ultraviolet light exposes the resist so that the pattern can be transferred to the wafer. The Micralign was a projection aligner rather than a contact aligner.^[1]

The Micralign traces part of its development to a higher-resolution aligner program and to work on proximity masking systems. Its earlier Microprojector used a 16-element lens system that produced an extremely focused light source and could produce 2.5 μm features, equal to the best contact aligners.^[1]

The Micralign fit into the repeated mask-alignment steps used to build up an integrated circuit design layer by layer. It was used after prior wafer processing had created an existing pattern that had to be precisely aligned with the next mask.^[1]

By the early 1970s, wafers had been about 2.5 inches in diameter and were moving to 3 inches. Existing optical systems were having problems with that size, and every new wafer size had required redesign of the optical systems from scratch.^[1]

The Micralign was used for semiconductor fabrication in photolithography and for patterning integrated circuits. The technology was developed in response to alignment problems in the early integrated circuit industry and to the needs of high-resolution masking.^[1]

The Air Force used integrated circuits in missile systems, including the Minuteman missile, and the Micralign's development traces to a contract aimed at improving a higher-resolution aligner for that context.^[1]