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Proceedings Paper

Chromium-based attenuated embedded phase-shift photomask blanks for use in 1X lithography
Author(s): Dan L. Schurz; Elizabeth Tai; Franklin D. Kalk
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Paper 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.

Paper Details

Date Published: 8 December 1995
PDF: 11 pages
Proc. SPIE 2621, 15th Annual BACUS Symposium on Photomask Technology and Management, (8 December 1995); doi: 10.1117/12.228204
Show Author Affiliations
Dan L. Schurz, Ultratech Stepper (United States)
Elizabeth Tai, Ultratech Stepper (United States)
Franklin D. Kalk, DuPont Photomasks, Inc. (United States)

Published in SPIE Proceedings Vol. 2621:
15th Annual BACUS Symposium on Photomask Technology and Management
Gilbert V. Shelden; James N. Wiley, Editor(s)

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