Neutron Reflectivity Characterization of the Photoacid Reaction-Diffusion Latent and Developed Images of Molecular Resists for Extreme Ultraviolet Lithography

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• 作者：Vivek M. Prabhu ; Shuhui Kang ; Jing Sha ; Peter V. Bonnesen ; Sushil Satija ; Wen-li Wu ; Christopher K. Ober
• 刊名：Langmuir
• 出版年：2012
• 出版时间：May 22, 2012
• 年：2012
• 卷：28
• 期：20
• 页码：7665-7678
• 全文大小：614K
• 年卷期：v.28,no.20(May 22, 2012)
• ISSN：1520-5827

文摘

Lithographic feature size requirements have approached a few radius of gyration of photoresist polymers used in thin-film patterning. Furthermore, the feature dimensions are commensurate with the photoacid diffusion length that defines the underlying latent image. Smaller imaging building blocks may enable reduced feature sizes; however, resolution limits are also dependent upon the spatial extent of the photoacid-catalyzed reaction diffusion front and subsequent dissolution mechanism. The reaction-diffusion front was characterized by neutron reflectivity for ccc stereoisomer-purified, deuterium-labeled tert-butoxycarbonyloxy calix[4]resorcinarene molecular resists. The spatial extent of the reaction front exceeds the size of the molecular resist with an effective diffusion constant of (0.13 卤 0.06) nm²/s for reaction times longer than 60 s, with the maximum at shorter times. Comparison to a mean-field reaction-diffusion model shows that a photoacid trapping process provides bounds to the spatial and extent of reaction via a reaction-limited mechanism whereas the ratio of the reaction rate to trapping rate constants recovers the effective diffusion peak. Under the ideal step-exposure conditions, surface roughness was observed after either positive- or negative-tone development. However, negative-tone development follows a surface-restructuring mechanism rather than etch-like dissolution in positive-tone development.