Characterization of Compositional Heterogeneity in Chemically Amplified Photoresist Polymer Thin Films with Infrared Spectroscopy

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• 作者：Shuhui Kang ; Bryan D. Vogt ; Wen-li Wu ; Vivek M. Prabhu ; David L. VanderHart ; Ashwin Rao ; Eric K. Lin ; Karen Turnquest
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：March 6, 2007
• 年：2007
• 卷：40
• 期：5
• 页码：1497 - 1503
• 全文大小：126K
• 年卷期：v.40,no.5(March 6, 2007)
• ISSN：1520-5835

文摘

We demonstrate a general approach to characterize compositional heterogeneity in polymer thinfilms using Fourier transform infrared (FTIR) spectroscopy. Polymer films with varying degrees of heterogeneitywere prepared using a model chemically amplified photoresist where a photoacid catalyzed reaction-diffusionprocess results in the formation of methacrylic acid (MAA) rich domains. Within these domains, the carboxylicacid groups dimerize through hydrogen bonding. FTIR measurements of the relative fraction of hydrogen-bondedvs free carboxylic groups are used to quantify the degree of compositional heterogeneity. The FTIR data fromcompositionally homogeneous systems, statistical copolymers, and polymer blends follow the expected lineardependence of the relative hydrogen-bonded fraction with composition. For the chemically amplified photoresistsystem, the FTIR data deviate substantially from that of the homogeneous distribution. Furthermore, parametersdescribing the size of the heterogeneity can be determined from a solid sphere model of the deprotected regionscatalyzed by the diffusing photoacid. The degree of the spatial heterogeneity varies with changes in the photoacidconcentration, reaction conditions, and initial copolymer composition. Increased nonreactive comonomer contentdecreases the degree of heterogeneity by reducing the hydrogen-bonding efficiency, which is consistent with thedilution of MAA groups.