In 1979, Electronics magazine reported that optical lithography would be a passing fancy superseded by direct write electron beam lithography by the year 1985. It was admitted in a follow-up article, written for that same magazine in 1985, that the demise of optical lithography had been predicted prematurely and that it would take until 1994 for shipments of optical wafer steppers to be of lower volume than those of x-ray step-and-repeat systems. It was expected that optical lithography, having reached a resolution limit of 0.5 μm, would need to be replaced. It is now 1996, and optical lithography is still going strong.
Much of optical lithography's longevity and productivity may be attributed to the extent to which fundamental problems have been identified, understood, and addressed. It is the authors' intention that this chapter should contribute toward an understanding by providing a clear explication of engineering problems inherent to optical lithography, along with a review of many of the contributions towards achieving this understanding and some of the ingenious solutions that have been devised along the way.
For the manufacture of integrated circuits, the lithographer has responsibility for creating the patterns of the desired sizes and shapes, overlaying these to prior patterns, and ensuring that the patterns are defect free. These three topics are the subjects of this chapter.
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