1 January 1994 Wafer steppers for the 64-M and 256-Mbit memory generations
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Optical wafer steppers are used in the fabrication of submicron and subhalf micron integrated circuits. The SIA Technology Roadmap has outlined the major requirements steppers must meet for the 64M and 256Mbit memory generations. These include 0.35 μm and 0.25 μm resolution over 22 and 27 mm square image fields. This article outlines these requirements and explores the impact on wafer stepper design and use. Stepper cost of ownership will be considered including the contribution of the reticle to the overall cost of the process.

Two major trends can be discerned. First, the requirement of 0.25 μm imaging over fields larger than a square inch forces the adoption of step and scan technologies as the cost and size of full field lenses grow noncompetitive. Second, in order to reduce the overall cost of ownership of the photolithography process, the industry is adopting mix-and-match strategies using high NA steppers to print critical mask layers and high speed, low NA, wide field steppers to print non-critical layers.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
William H. Arnold, Gary C. Escher, "Wafer steppers for the 64-M and 256-Mbit memory generations", Proc. SPIE 10273, 64-to 256-Megabit Reticle Generation: Technology Requirements and Approaches: A Critical Review, 1027305 (1 January 1994); doi: 10.1117/12.177438; https://doi.org/10.1117/12.177438


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