title: Selective Fragmentation of Radiation-Sensitive Novel Polymeric Resist Materials by Inner-Shell Irradiation.
abstract: Two key concepts in extreme ultraviolet lithography (EUVL) are important for it to be a candidate for the mass production of future integrated circuits: the polymer formulation and the photofragmentation process. In this work, both concepts were carefully studied. The design and synthesis of radiation-sensitive organic polymeric materials based on the inclusion of a radiation-sensitive tetrahydrothiophenium functional group are outlined. A 1-(4-methacryloyoxy)naphthalene-1-yl)tetrahydro-1H-thiophenium trifluoromethanesulfonate (MANTMS) monomer containing the tetrahydrothiophenium group undergoes homo- and copolymerizations using free-radical polymerization with a 2,2'-azobis(isobutyronitrile) initiator. The surface photodegradation and oxidation of these novel polymeric materials were investigated using highly monochromatized soft X-rays from synchrotron radiation at the carbon K-edge excitation region. An efficient functionalization was observed when the excitation energy was tuned to C 1s → π*C═C. A high rate of defluorination and a loss of sulfonated groups as a result of an increase in the irradiation time for the MANTMS homopolymer thin films were mainly observed under the π*C═C excitation of the naphthyl functional groups. On the contrary, excitation similar to C 1s → π*C═O or C 1s → σ*C-F did not produce important degradation, showing a highly selective process of bond breaking. Additionally, the presence of methyl methacrylate copolymer in the original MANTMS yielded a much higher degree of stability against inner-shell radiation damage. Our results highlight the importance of choosing the right polymer formulation and excitation energy to produce a sensitive material for EUVL without using the concept of chemical amplification.
authors.affiliation: †Department of Chemical Physics, Chemical Institute, UFRGS, Porto Alegre, Postal Code 91501-970, Rio Grande do Sul, Brazil.
authors.forename: Gabriela Ramos
authors.initials: GR
authors.lastname: Chagas
authors.affiliation: ‡School of Basic Sciences, Indian Institute of Technology Mandi, Mandi-175001, Himachal Pradesh, India.
authors.forename: Vardhineedi Sri Venkata
authors.initials: VS
authors.lastname: Satyanarayana
authors.affiliation: §School of Chemistry and Food, Federal University of Rio Grande, Avenida Itália km 8, Postal Code 96.201-900, Rio Grande, Rio Grande do Sul, Brazil.
authors.forename: Felipe
authors.initials: F
authors.lastname: Kessler
authors.affiliation: †Department of Chemical Physics, Chemical Institute, UFRGS, Porto Alegre, Postal Code 91501-970, Rio Grande do Sul, Brazil.
authors.forename: Guilherme Kretzmann
authors.initials: GK
authors.lastname: Belmonte
authors.affiliation: ‡School of Basic Sciences, Indian Institute of Technology Mandi, Mandi-175001, Himachal Pradesh, India.
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Gonsalves
authors.affiliation: †Department of Chemical Physics, Chemical Institute, UFRGS, Porto Alegre, Postal Code 91501-970, Rio Grande do Sul, Brazil.
authors.forename: Daniel Eduardo
authors.initials: DE
authors.lastname: Weibel
keywords: EUV degradation; inner-shell excitation; nonchemically amplified resist; surface functionalization; synchrotron radiation