26 June 2003 Application of in-situ aberration measurements to pattern-specific imaging optimization
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With the advent of in-situ aberration measurement, users may now gather a 'snapshot’ of a given lens’ aberration fingerprint following installation of the exposure tool in their fab. This paper will detail how this information may be used as input data into an optimization routine whose final output is a set of lens adjustments that will yield improved imaging performance. It will be shown that a lens with many reliable degrees of adjustment freedom can offer a wide range of optimization options. For example, for some process levels, a fixed focus latitude requirement is well defined, and it often is desirable to optimize the CD distribution over that available focus range. For other levels, there may be a strict 'image shift’ requirement over a specified focus range. In general, such optimization should include some combination of imaging performance targets. Within some limits, the user may specify the imaging performance priorities, and an optimization routine can be executed. The optimization routine may in principle allow manipulation of all available lens adjustment degrees of freedom, ending with a lens adjustment prescription that delivers the optimum result in terms of the user-specified priorities. Examples of such optimization, showing the expected improvement in the imaging performance, will be presented through image simulation results.
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Steve D. Slonaker, Steve D. Slonaker, Robert J. Chung, Robert J. Chung, "Application of in-situ aberration measurements to pattern-specific imaging optimization", Proc. SPIE 5040, Optical Microlithography XVI, (26 June 2003); doi: 10.1117/12.485534; https://doi.org/10.1117/12.485534

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