Articles

Water immersion of model photoresists: interfacial influences on water concentration and surface morphology

[+] Author Affiliations
Bryan D. Vogt, Christopher L. Soles, Chia-Ying Wang, Vivek M. Prabhu, Patricia M. McGuiggan, Jack F. Douglas, Eric K. Lin, Wen-li Wu

National Institute of Standards and Technology, Polymers Division, Gaithersburg, Maryland?20899

Sushil K. Satija

National Institute of Standards and Technology, Center for Neutron Research, Gaithersburg, Maryland?20899

Darı´o L. Goldfarb, Marie Angelopoulos

IBM T. J. Watson Research Center, Yorktown Heights, New York?10598

J. Micro/Nanolith. MEMS MOEMS. 4(1), 013003 (Feb. 10, 2005). doi:10.1117/1.1861852
History: Received Jun. 4, 2004; Accepted Jul. 8, 2004; Feb. 10, 2005; Online February 10, 2005
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The emergence of immersion lithography as a potential alternative for the extension of current lithography tools requires a fundamental understanding of the interactions between the photoresist and an immersion liquid such as water. The water concentration depth profile within the immersed photoresist films is measured with neutron reflectometry. The polymer/substrate interface affects both the water concentration near the interface and the surface morphology of the film. Immersed films are not stable (adhesive failure) over the course of hours when supported on a silicon wafer with a native oxide surface, but are stable when the substrate is first treated with hexamethyldisilazane (HMDS). The bulk of the polymer films swells to the equilibrium water concentration, however, a gradient in water concentration is observed near the polymer/HMDS substrate interface with a concentration of approximately 17% by volume fraction and extending up to 50 Å into the film. Thus, polymers that absorb more than this amount exhibit depletion near the interface, whereas polymers that absorb less exhibit a water excess layer. These concentration gradients extend approximately 50 Å away from the interface into the film. As the total film thickness approaches this length scale, the substrate-induced concentration gradients lead to a film-thickness-dependent swelling; enhanced or suppressed swelling is witnessed for the excess or depleted interfacial concentrations, respectively. The substrate also influences the surface morphology of immersed thin films. The film surface is smooth for the HMDS-treated substrate, but pin-hole defects with an average radius of 19±9nm are formed in the films supported on the native oxide substrates. © 2005 Society of Photo-Optical Instrumentation Engineers.

© 2005 Society of Photo-Optical Instrumentation Engineers

Citation

Bryan D. Vogt ; Christopher L. Soles ; Chia-Ying Wang ; Vivek M. Prabhu ; Patricia M. McGuiggan, et al.
"Water immersion of model photoresists: interfacial influences on water concentration and surface morphology", J. Micro/Nanolith. MEMS MOEMS. 4(1), 013003 (Feb. 10, 2005). ; http://dx.doi.org/10.1117/1.1861852


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