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12 June 2003 Fluoropolymer resists for 157 nm lithography
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Fluoropolymers have been shown to be one of the best materials for high transparency of 157 nm wavelength radiation. Both resists and pellicles are being designed from such materials. One of our approaches to improved transparency for 157 nm resists is based upon fluorinated variations of polymethacrylate and polyhydroxystyrene derivatives. Lithographic studies were carried out on experimental resist platforms using 157 nm and 248 nm steppers, and it was shown that, after selective modification, it is possible to use conventional resist backbones, such as acrylic or styrenic, in the design of single-layer resists for 157 nm lithography. It has been demonstrated in our studies that 157 nm absorbance of these materials can be as low as 1.5-2.0μm-1. Another approach to 157 nm resist design is based upon fluorinated backbone variations. Research will be described focusing on several new monomers having fluorine functions such as -F and -CF3 groups near a polymerizable double bond to improve transparency at 157 nm and to raise the resist glass transition temperature compared to their hydrocarbon analogues. Due to the lower electron density of the double bond, these monomers can be copolymerized with electron-rich vinyl monomers. As an extension to this strategy, we are synthesizing novel fluoropolymers having partially fluorinated monocyclic structures with radical cyclo-polymerization. These polymers have the C-F bond on the polymer main chain and also possess acid labile groups as part of a ring structure to eliminate degassing. In order to further enhance the transparency of these systolic polymers at 157 nm, we have eliminated the carbonyl group. The cyclic nature of the polymer will result in a high glass transition temperature.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Vaishali Raghu Vohra, Xiang-Qian Liu, Katsuji Douki, Christopher Kemper Ober, Will Conley, Paul Zimmerman, and Daniel Miller "Fluoropolymer resists for 157 nm lithography", Proc. SPIE 5039, Advances in Resist Technology and Processing XX, (12 June 2003);

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