Decarboxylation efficiency of carboxylic acids as ligands of metal oxide nanocluster resists upon γ-ray irradiation

Abstract

Metal oxide nanocluster resists have recently attracted considerable attention for use in extreme ultraviolet (EUV) lithography. To obtain sophisticated guidelines for material design, it is necessary to understand well the radiation-induced chemical reaction scheme including the insolubilization mechanism. In this study, the production of CO2, which is considered to be one of the end products of treatment with an ionizing radiation, was investigated for eight types of carboxylic acid under various conditions using -rays (60Co) as a radiation source. The amount of CO2 produced was measured by gas chromatography (GC). GCO2 (/100 eV), which indicates decarboxylation efficiency, was evaluated. CO2 was generated through electron addition, hole transfer, and hydroxyl radical addition to the molecular and ionic forms of carboxylic acids. The dependences of GCO2 on reaction partners were clarified. The dependences of GCO2 on the molecular structure and dissociative state of carboxylic acids were also clarified.

Sensitization mechanism of metal oxide nanocluster resists with carboxylic acid ligands

“…On the basis of the results in Figs. 4-6 and the reaction mechanism reported in previous studies, 4,19,20,22) the molecular structures of end products were estimated and are shown in Fig. 7.…”

“…study. 4,19,20,22) Figure 4(a) shows the mass spectrum of the irradiated MAA aqueous solution with no additive. Under this condition, the reactions initiated by a hydrated electron and a hydroxyl radical proceed.…”

“…Under this condition, the reactions initiated by a hydrated electron and a hydroxyl radical proceed. 22) The horizontal axis represents the molecular weight per charge m/z, which ranges from 150 (the lower limit of detection) to 1000. An enlarged graph (from m/z 290 to 390) is also shown in Fig.…”

“…18,21) In this study, we analyzed the end products produced by ionizing radiation in order to clarify the reaction mechanism following the initial reactions clarified in the previous studies. 4,19,20) In our previous work, 22) the production of CO 2 , which is considered to be one of the end products, was investigated for eight types of carboxylic acids under various conditions using γ-rays ( 60 Co) as a radiation source. The dependence of the G value of CO 2 (G CO2 ) on the molecular structure of carboxylic acids and reaction partners was clarified by gas chromatography.…”

“…The dependence of the G value of CO 2 (G CO2 ) on the molecular structure of carboxylic acids and reaction partners was clarified by gas chromatography. 22) The G value refers to the number of molecules of the reactant consumed or the product formed per 100 eV of energy absorbed. In this study, the sensitization mechanism including the insolubilization mechanism is discussed on the basis of the results of analyzing the end products by electrospray ionization mass spectrometry (ESI-MS), high-performance liquid chromatography (HPLC), and dynamic light scattering (DLS).…”