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### Journal of Micro/Nanolithography, MEMS, and MOEMS

Water immersion of model photoresists: interfacial influences on water concentration and surface morphology
Author(s): Bryan D. Vogt; Christopher L. Soles; Chia-Ying Wang; Vivek M. Prabhu; Patricia M. McGuiggan; Jack Douglas; Eric K. Lin; Wen-Li Wu; Sushil K. Satija; Dario L. Goldfarb; Marie Angelopoulos
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Paper Abstract

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±9 nm are formed in the films supported on the native oxide substrates.

Paper Details

Date Published: 1 January 2005
PDF: 6 pages
J. Micro/Nanolith. MEMS MOEMS 4(1) 013003 doi: 10.1117/1.1861852
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 4, Issue 1
Show Author Affiliations
Bryan D. Vogt, National Institute of Standards and Technology (United States)
Christopher L. Soles, National Institute of Standards and Technology (United States)
Chia-Ying Wang, National Institute of Standards and Technology (United States)
Vivek M. Prabhu, National Institute of Standards and Technology (United States)
Patricia M. McGuiggan, National Institute of Standards and Technology (United States)
Jack Douglas, National Institute of Standards and Technology (United States)
Eric K. Lin, National Institute of Standards and Technology (United States)
Wen-Li Wu, National Institute of Standards and Technology (United States)
Sushil K. Satija, National Institute of Standards and Technology (United States)
Dario L. Goldfarb, IBM Thomas J. Watson Research Ctr. (United States)
Marie Angelopoulos, IBM Thomas J. Watson Research Ctr. (United States)