Green Lithography Using Water-Developable Sugar-Based Negative Resist Materials
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Green Lithography Using Water-Developable Sugar-Based Negative Resist Materials Satoshi Takei1, Makoto Hanabata1, Kigen Sugahara1, Naoto Sugino2, Takao Kameda2, and Jiro Fukushima3 1 Toyama Prefectural University, Imizu, Toyama 939-0398, Japan 2 Sanko gosei, Koreyasu Nanto, Toyama 939-1852, Japan 3 Toyama Prefectural Plastic Industries Association, Toyama, Toyama 930-0866, Japan ABSTRACT A water-developable sugar-based negative resist material was developed. This material enables the use of pure water in the development process of electron beam (EB) green lithography instead of conventionally used aqueous alkaline developers and organic solvents. The sugar-based negative resist material was developed by replacing the hydroxyl groups in alpha-linked disaccharides with EB-sensitive 2-methacryloyloxyethyl groups. The sugar-based negative resist material features highly efficient crosslinking and low film thickness shrinkage under EB irradiation. It is demonstrated to be applicable to green lithography with a 100– 500 nm line-and-space pattern and an EB exposure dose of 18 μC/cm2. INTRODUCTION The use of plant products in lithography has been increasing for eco-friendly manufacturing processes; the use of plant products in this application necessitates the development of new techniques such as organic-solvent-free spin-coating and water-developable resist materials. In this study, we report progress in the characterization of a water-developable, non-chemically amplified, negative tone resist material derived from biomass with the sugar chain structure serving as a backbone of a linear polymer; we also developed a pure water development process for electron beam (EB) lithography. In the development process commonly used in lithographic methods, resist materials are dipped in an aqueous alkaline solution developer of tetramethylammonium hydroxide (TMAH) in pure water. Water-developable resist materials have been developed in photolithography [1-10]. In our previous studies, we reported resist materials derived from biomass such as sugar and cellulose [11-16]. In environmentally compatible green lithography for biomedical, pharmaceutical, optical, and electronic devices, the use of a developer process that involves water rather than TMAH or organic solvents is preferred to circumvent issues related to potential health effects, toxicity, and environmental safety. The use of water-based developer processes also provides easier handling and promotes resource conservation. The material design concept of using an interface in combination with a water-developable sugar-based resist material has been suggested to cause crosslinking of two materials between the bottom of the resist and the surface of the underlayer under EB irradiation; this approach has also been reported to prevent resist-pattern collapse during the water-developable process. Figure 1 shows a schematic of chemical adhesion by radical polymerization between the EB-curable groups of a water-developable sugar resist and hardmask materials for reduction of resist-p
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