20 August 1986 Alignment Wavelength Optimization For Wafer Stepper Microscope
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In modern photolithography, alignment to targets which are burried under layers of highly absorptive coatings at the actinic wavelength, is a severe problem. A novel optical technique has been developed at TRE allowing the use of an arbitrary optical wavelength for target alignment. Significant improvement in target image quality and in system alignment accuracy has been achieved when the alignment wavelength is optimized for minimum process layer absorption and stepper lens aberration. In this paper, the optical approach which corrects for chromatic aberration and astigmatism of the stepper lens will be described. Technical data with a number of commonly used, highly absorptive materials will be presented. Better than 0.25 micron three sigma alignment in realistic absorptive process layers has been achieved with this technique.
© (1986) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sungmuk Lee, Shi-kay Yao, Michele Nuhn, "Alignment Wavelength Optimization For Wafer Stepper Microscope", Proc. SPIE 0633, Optical Microlithography V, (20 August 1986); doi: 10.1117/12.963705; https://doi.org/10.1117/12.963705


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