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30 July 2002 Design and fabrication of customized illumination patterns for low-k1 lithography--a diffractive approach: II. Calcium fluoride controlled-angle diffusers
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Abstract
As CDs continue to shrink, lithographers are moving more towards using off-axis illumination schemes to increase their CD budget. There have been several papers over the last few years describing various custom illumination profiles designed for application specific optimization. These include various annular and quadrupole illumination schemes including weak quadrupole, CQUEST, and QuasarTM. Diffractive optics, if incorporated into the design of the illumination system, can be used to create arbitrary illumination profiles without the associated light loss, thus maintaining throughput while optimizing system performance. Diffractive optical elements used to generate efficient illumination profiles for 248 nm and 193 nm excimer laser-source scanners, have been reported and realized in fused silica. The fabrication of such elements in calcium fluoride (CaF2), for use in 157 nm wavelength lithographic projection tools has been developed and is presented in this paper. Three different categories of elements are shown: large-diagonal-cluster diffusers, medium- and small-rectangular-cluster diffusers. The diffusers were fabricated as binary phase devices, in order to determine calcium fluoride processing capabilities.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Menelaos K Poutous, Marc D. Himel, William F. Delaney, Jared D. Stack, Alan D. Kathman, Adam S. Fedor, Robert E. Hutchins, and Jerry L. Leonard Jr. "Design and fabrication of customized illumination patterns for low-k1 lithography--a diffractive approach: II. Calcium fluoride controlled-angle diffusers", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); https://doi.org/10.1117/12.474543
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