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8 December 1995 Chromium-based attenuated embedded phase-shift photomask blanks for use in 1X lithography
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Abstract
Process latitude, especially depth of focus (DOF), is an ever-growing concern to semiconductor and thin film head (TFH) manufacturers. It is well known that as lithographers pursue smaller linewidth resolution through the use of larger numerical apertures (NA) and smaller exposure wavelengths, DOF continues to shrink. TFH manufacturers are faced with the additional burdens of thick resist and high aspect ratios. One successful method of regaining a portion of the lost DOF in i-line reduction lithography is the use of phase shift masks. There are a variety of phase shift mask types that typically involve a conventional chrome mask with an added layer of shifter material adjacent to specific geometries. Another type, without added shifter material, requires a second etch into the quartz substrate. Compared to conventional masks, these mask types require additional patterning and processing steps. Because of their high cost and technical limitations, phase shift masks are frequently used only for contact layers in i-line processes. Attenuated embedded phase shift (AEPS) masks have the potential to improve depth of focus for 1X g/h-line systems. Because the shifter material is incorporated in the substrate, these masks can be patterned and processed similar to conventional chrome masks. Consequently, their cost is much lower than other phase shift mask types and their applications are not limited by dense geometries.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Dan L. Schurz, Elizabeth Tai, and Franklin D. Kalk "Chromium-based attenuated embedded phase-shift photomask blanks for use in 1X lithography", Proc. SPIE 2621, 15th Annual BACUS Symposium on Photomask Technology and Management, (8 December 1995); https://doi.org/10.1117/12.228204
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