| 초록 |
Acetal and t-butyl ester groups have been used as protecting groups for carboxylic acid in the matrix polymers for ArF chemically amplified resists. However, the polymers with these protecting groups release the volatile byproducts such as ethyl vinyl ether, or isobutene by the acid-catalyzed deprotection reaction. All these molecules will outgas from the resist film during the lithographic process. This outgassing causes volume shrinkage of the resist film and extensive damage to optical lenses of exposure tools. Transmission loss and severe image distortion can take place due to this resist outgassing. The purpose of our study is to apply a novel method of polarity change, ring-opening instead of deprotection for a chemically amplified resist system in order to eliminate the resist outgassing. We designed and synthesized a new acid labile group, 7,7-dimethyloxepan-2-one, which was introduced into the matrix polymers for ArF positive chemically amplified resists. The 7,7-dimethyloxepan-2-one group was readily cleaved and the carboxylic acid functionality was formed by acid-catalyzed ring-opening reaction in the exposed region after post-exposure bake. Monomers and polymers containing 7,7-dimethyloxepan-2-one group were synthesized by oxidation of cyclic ketones such as derivatives of bile acids. 3-Chloroperbenzoic acid were used as oxidizing agents of those cyclic ketones. FT-IR and NMR investigation confirmed the acid-catalyzed ring opening reaction of the 7,7-dimethyloxepan-2-one. The matrix polymer does not release the gaseous byproducts due to the ring-opening reaction. The sub-0.3 μm patterns were obtained with a conventional developer using an ArF exposure tool. |
