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Publication Citation: Water Distribution Within Immersed Polymer Films

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Author(s): B D. Vogt; Christopher L. Soles; Vivek M. Prabhu; Sushil K. Satija; Eric K. Lin; Wen-Li Wu;
Title: Water Distribution Within Immersed Polymer Films
Published: February 01, 2005
Abstract: The emergence of immersion lithography as a potential alternative for the extension of current lithography tools will require a fundamental understanding of the interactions between the photoresist and the immersion liquid such as water. The water concentration depth profile within the immersed photoresist films was measured with neutron reflectometry. The bulk of the polymer films swelled to the equilibrium water concentration, however a gradient in water concentration was observed near the polymer/substrate interface. Dependent on the relative hydrophilicity of the photoresist and the substrate, either a depletion or excess of water was observed at the interface. Using HMDS treated silicon wafers as the substrate results in approximately 17 % water by volume at the interface.The interfacial concentration decreases (or increases) to the bulk water solubility limit approximately 50 from the substrate. 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. Variation of the substrate surface energy allows for tuning of the interfacial water concentration, ranging from 30 % to less than 1 % water by volume.
Conference: SPIE Advanced Lithography
Proceedings: Proceedings of SPIE
Volume: 5753
Pages: pp. 31 - 39
Location: San Jose, CA
Dates: February 28-March 4, 2005
Keywords: lithography,reflectivity,thin films
Research Areas: Polymers
PDF version: PDF Document Click here to retrieve PDF version of paper (126KB)