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A new optical system has recently been designed, built, and tested to meet the demands of large area lithography applications. The new optical system is referred to as Scanning Array Lens LithographY (SALLY) and is based on the well-known Wynne Dyson 1:1 projection lens configuration that has found widespread use in the IC, thin-film head, and micromachining industries. Recent advances in the areas of optical design, alignment, assembly and packaging have led to the development of an array lens that essentially projects a single elongated field that can be extended to span the width of any substrate. This enables a substrate to be exposed in a single scanning motion. The array lens is composed of multiple compact, catadioptric lens relays having trapezoidal shaped image fields that are positioned in an alternating and overlapping fashion. The resulting imaging capability is indistinguishable from that which would be accomplished by a single very large, well-corrected lens. Features exposed in the transition between separate fields exhibit no visible variations in their structures. This paper describes a three field prototype SALLY system composed of lens relays with a numerical aperture (NA) of 0.10 designed to include the g- and h-lines of the mercury spectrum. This NA was selected to provide a useful combination of resolution, depth-of-focus, and exposure irradiance for a range of applications including micromachining. Test results demonstrate a seamless transition between separate image fields and resolution of equal line/space patterns down to 2.3 micrometers . Thick resist film imagery showing thickness to linewidth aspect ratios of up to 4:1 using conventional application and development techniques are also shown.
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