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Proceedings Paper

Transparency vs. efficiency in 193-nm photoacid generator design
Author(s): Gerd Pohlers; Yasuhiro Suzuki; Nicholas Chan; James F. Cameron
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Paper Abstract

The advent of 193nm lithography has stimulated the search for novel photocid generators (PAGs) with increased transparency at 193nm. This need for more transparency stems from the use of phenyl groups in the classic 248nm PAGs, such as triphenylsulfonium salts. Unfortunately for 193nm resist development, the phenyl group is highly absorbing at that wavelength, thereby severely restricting the PAG formulation space. It has not yet been pointed out, however, that photoacid generation efficiency has also become more important for 193nm systems. The reason is that 193 polymers cannot sensitize the PAG, as is the case for 248nm phenolic systems, i.e. the light absorbed by the polymer does not contribute to acid generation. Furthermore, the photoacid generation efficiency of sulfonium PAGs drops considerably when going from 248nm to 193nm. Thus, the ability to quantify the photoefficiency of a new PAG quickly becomes key to successful new 193nm PAG development. While there are many ways to determine the quantum yield of photoacid generation ((Phi) ) of PAGs, they are usually time and labor-intensive. Therefore, in the first part of this paper, we describe the P-parameter as a fast, simple and more practical way than the quantum yield, (Phi) to characterize the photoefficiency of a PAG. Results for a number of sulfonium PAGs at both 248 and 193nm are determined this way, and the observed trends are discussed. In the second part of this work we investigate how lithographic performance is impacted by those two parameters. A transparency/efficiency matrix of nine PAGs is evaluated in a 193nm standard resist formulation. The results indicate that the PAGs with a combination of high efficiency and transparency yield the best lithographic results, underlining the importance of efficiency as a key parameter in 193nm PAG design.

Paper Details

Date Published: 24 July 2002
PDF: 13 pages
Proc. SPIE 4690, Advances in Resist Technology and Processing XIX, (24 July 2002); doi: 10.1117/12.474217
Show Author Affiliations
Gerd Pohlers, Shipley Co. Inc. (United States)
Yasuhiro Suzuki, Shipley Co. Inc. (United States)
Nicholas Chan, Shipley Co. Inc. (United States)
James F. Cameron, Shipley Co. Inc. (United States)

Published in SPIE Proceedings Vol. 4690:
Advances in Resist Technology and Processing XIX
Theodore H. Fedynyshyn, Editor(s)

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