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.

EUV photofragmentation study of hybrid nonchemically amplified resists containing antimony as an absorption enhancer

“…In the last years we have studied the photofragmentation of several n-CAR homopolymers and co-polymers under EUV synchrotron radiation (SR) excitation. 4,9,15,16,21 The obtained results showed that the photodegradation processes affected mainly the triate group but also the carbon backbone of the resists. In those works it was hypothesized that the neutral sulde Ar-S-CH 3 is formed aer irradiation rendering the irradiated area insoluble in the developer.…”

“…[4][5][6][7][8][9][10][11][12][13][14][15] The design paradigm has to incorporate the basic principles of conventional resists superimposed with the specic requirements of EUVL for attaining the lower nodes. 12,15,16 The interaction of the resist thin lms with high energy EUV photons (13.5 nm) is a very complex process triggered by EUV radiation that breaks the chemical bonds and simultaneously produces ablation and a high yield of secondary electrons. 15,16 This results in degassing which causes chemical and morphological changes in the resist surface.…”

“…12,15,16 The interaction of the resist thin lms with high energy EUV photons (13.5 nm) is a very complex process triggered by EUV radiation that breaks the chemical bonds and simultaneously produces ablation and a high yield of secondary electrons. 15,16 This results in degassing which causes chemical and morphological changes in the resist surface. One of the key challenges in EUVL is simultaneously meeting resist performance targets like sensitivity, resolution, etch resistance, and line edge roughness (LER).…”

Polarization Dependence in the Carbon K-Edge Photofragmentation of MAPDST Photoresist: An Experimental and Theoretical Study

“…In one of our studies, a selective bond dissociation process was observed when the excitation energy was tuned to the C 1s → π CC * transition (285.3 eV). 42 A high rate of defluorination and a loss of sulfonated groups were measured mainly at 285.3 eV of excitation energy. However, similar excitations to C 1s → π CO * or C 1s → σ C−F * did not produce important fragmentation, leading to an efficient preservation of the original chemical structures of the resists.…”

“…In recent years, we have studied the photochemistry and oxidation mechanisms of several resists to be used in extreme ultraviolet lithography (EUVL) for the next generation of integrated circuits. − Those investigations were an attempt to understand the complex photofragmentation mechanisms after extreme ultraviolet (EUV) or inner shell excitation using SR. In one of our studies, a selective bond dissociation process was observed when the excitation energy was tuned to the C 1s → π CC * transition (285.3 eV) . A high rate of defluorination and a loss of sulfonated groups were measured mainly at 285.3 eV of excitation energy.…”