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Proceedings Paper

Low surface energy polymeric release coating for improved contact print lithography
Author(s): David P. Mancini; Douglas J. Resnick; Kathleen A. Gehoski; Laura L. Popovich; Daniel Chang
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Paper Abstract

Contact printing has been used for decades in many various lithography applications in the microelectronic industry. While vacuum contact printing processes offer sub-micron resolution and high throughput, they often suffer from some important drawbacks. One of the most common problems is degradation in both resolution and defect density which occurs when the same mask si used for multiple exposures without frequent mask cleans. This is largely due to the relatively high surface energy of both quartz and chrome and the tendency of most photoresists to adhere to these surfaces. As a result, when a mask and wafer are pressed into intimate contact, resist will tend to stick to the mask creating a defect on the wafer, effectively propagating defects to subsequent wafers. In this study, DuPont Teflon AF 1601S is used as a photomask coating and evaluated for its ability to act as a release agent and reduce defects while maintaining resolution for multiple exposures. Teflon AF is an amorphous, transparent, low surface energy, polymeric material that can be spin coated into a thin conformal film. Tests have shown that when using an uncoated mask in vacuum contact, resolution of 0.75 micrometers dense lines is severely degraded after less than 10 consecutive exposures. However, when the mask is coated, 0.75 micrometers dense lines were successfully resolved using vacuum contact for over 200 exposures without cleaning. In addition, it has been demonstrated that Teflon AF coatings impart to a mask a self-cleaning capability, since particles tend to stick to the photoresist rather than the mask. A coated mask, which was purposefully contaminated with particulates, resolved 0.75 micrometers dense lines on all but the first wafer of a series of 25 consecutive exposures. The patented mask releases layer process has successfully been demonstrated with a positive novolak resist. Additional data which describes the system chemistry, dilution and coating process, and film morphology are also presented.

Paper Details

Date Published: 3 October 2001
PDF: 7 pages
Proc. SPIE 4562, 21st Annual BACUS Symposium on Photomask Technology, (3 October 2001); doi: 10.1117/12.458339
Show Author Affiliations
David P. Mancini, Motorola (United States)
Douglas J. Resnick, Motorola (United States)
Kathleen A. Gehoski, Motorola (United States)
Laura L. Popovich, Motorola (United States)
Daniel Chang, Motorola (United States)

Published in SPIE Proceedings Vol. 4562:
21st Annual BACUS Symposium on Photomask Technology
Giang T. Dao; Brian J. Grenon, Editor(s)

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