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Proceedings Paper

Silsesquioxane-based 193 nm bilayer resists: characterization and lithographic evaluation
Author(s): Hiroshi Ito; Hoa D. Truong; Sean D. Burns; Dirk Pfeiffer; Wu-Song Huang; Mahmoud M. Khojasteh; P. Rao Varanasi; Mike Lercel
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Paper Abstract

Polysilsesquioxane-based 193 nm positive bilayer resists are described. In this design Si for etch resistance is placed in every repeat unit and acid-labile protected and acidic groups (and polar units) are in the side chain, allowing to incorporate each lithographically critical functionality in sufficient quantity. Fluoroalcohol is employed as an acid group instead of carboxylic acid because of its more attractive dissolution properties. Polymers were carefully analyzed by 19F, 13C, and 29Si NMR to determine composition and to quantify residual acetyl, silanol, and Q/T. Hydrogen-bonding between tertiary ester and fluoroalcohol in the polysilsesquioxanes was investigated by FT-IR and the effect of lactone incorporation on the thermal deprotection temperature elucidated. In order to better understand the dissolution behavior of exposed resist films, the silsesquioxane resist polymers were partially (ca. 30%) and fully deprotected in solution with acid and their dissolution kinetics investigated by using a quartz crystal microbalance (QCM). It has been found that the exposed areas of the silsesquioxane resists can have a very fast dissolution rate (Rmax) of >20,000 A/sec (or even >100,000 A/sec). Heating the fully deprotected model polymers to 150°C did not reduce the dissolution rate much, suggesting thermal condensation of silanol end groups is insignificant. Model deprotected polymers containing triphenylsulfonium nonaflate were exposed to 254 nm radiation, baked, and subjected to QCM measurements in order to determine whether or not acid-catalyzed silanol condensation would reduce the dissolution rate. A combination of high dose and high temperature bake resulted in significant reduction of the dissolution rate in the silsesquioxane polymer containing a small trifluoroalcohol. However, the dissolution behavior of the polymer bearing a bulky norbornene hexafluoroalcohol was unaffected by exposure and bake. Chemical and development contrast curves were generated by using a temperature gradient plate and bake temperature effects investigated. While a postapply bake temperature variation from 95 to 130°C did not affect the contrast (chemical and development) and sensitivity, a postexposure bake temperature effect was quite small. The process window of the silsesquioxane bilayer resists was comparable to that of a high performance commercial 193 nm single layer resist for both isolated and nested contact hole imaging, Superior performance of our silsesquioxane resist was demonstrated in patterned etch in comparison with a COMA-based bilayer resist.

Paper Details

Date Published: 4 May 2005
PDF: 13 pages
Proc. SPIE 5753, Advances in Resist Technology and Processing XXII, (4 May 2005); doi: 10.1117/12.598847
Show Author Affiliations
Hiroshi Ito, IBM Almaden Research Ctr. (United States)
Hoa D. Truong, IBM Almaden Research Ctr. (United States)
Sean D. Burns, IBM T.J. Watson Research Ctr. (United States)
Dirk Pfeiffer, IBM T.J. Watson Research Ctr. (United States)
Wu-Song Huang, IBM Microelectronics Div. (United States)
Mahmoud M. Khojasteh, IBM Microelectronics Div. (United States)
P. Rao Varanasi, IBM Microelectronics Div. (United States)
Mike Lercel, IBM T.J. Watson Research Ctr. (United States)
IBM Microelectronics Div. (United States)


Published in SPIE Proceedings Vol. 5753:
Advances in Resist Technology and Processing XXII
John L. Sturtevant, Editor(s)

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