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The Mann 4800 Direct Step on Wafer, or DSW, is the true grandfather of all modern steppers. It was derived from an earlier David W. Mann photo-repeater used for mask making. Introduced in the early seventies by GCA, the Mann 4800 soon revolutionized wafer exposure, obsolescing not only contact and proximity aligners but projection aligners as well. It could easily reach critical dimensions of one micron, about 5 times better than projection aligners could do.
While that got the industry’s attention loud and clear, it was
really the enhanced overlay registration of the system that swung
them over. Perkin Elmer’s vain attempt to re-invent projection aligners led to that company’s ultimate demise. Before then however, the projection aligner was merged with the stepping aligner to become the modern-day scanning stepper.
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