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17 May 1994 Minimization of total overlay errors when matching nonconcentric exposure fields
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Abstract
As stepper field sizes increase, integrated circuit manufacturers are faced with a new series of challenges in matching exposure tools. Existing fabrication lines with smaller field steppers must determine how to match new, large field tools to their existing steppers. For optimum efficiency, one would prefer to expose a larger number of die per field on the larger field lenses. From a manufacturing standpoint, it is also necessary to expose some layers of these devices on the smaller field tools, which are limited to a smaller number of die per field. This requires matching non-concentric fields, placing two or more exposure fields of the smaller lenses within a single exposure field of the larger lenses. This paper discusses the potential overlay problems associated with non-concentric matching, and presents our methodology for determining the overlay capability and optimum matching strategy for such a scenario. We present data and simulations showing how overlay is affected by different configurations of these non-concentric fields, and solutions to minimize total overlay errors.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Moshe E. Preil, Terry M. Manchester, Anna Maria Minvielle, and Robert J. Chung "Minimization of total overlay errors when matching nonconcentric exposure fields", Proc. SPIE 2197, Optical/Laser Microlithography VII, (17 May 1994); https://doi.org/10.1117/12.175466
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