Daisuke Shimizu

A novel noria (water-wheel-like cyclic oligomer) derivative as a chemically amplified electron-beam resist material

A novel ladder-type cyclic oligomer (molecular water-wheel = noria) derivative containing t-butyl ester groups was synthesized. This derivative (noria-COOtBu) had good thermal stability, good solubility in common organic solvents, and good film-forming ability. The photo-induced deprotection (UV irradiation for 30 min followed by heating at 130 °C) of films of noria-COOtBu was examined in the presence of a photo-acid generator, and it was found that deprotection of the t-butyl groups proceeded smoothly to give the corresponding carboxylic acid derivative (noria-COOH). Furthermore, when noria-COOtBu(71) (ratio of t-butyl ester groups: 71%) was examined as an electron-beam resist material, a clear line and space pattern was obtained at a resolution of 70 nm.

Difference between Acid Generation Mechanisms in Poly(hydroxystyrene)- and Polyacrylate-Based Chemically Amplified Resists upon Exposure to Extreme Ultraviolet Radiation

Chemically amplified resists have been used in the mass production of semiconductors. Poly(hydroxystyrene)-based resists have been extensively developed for KrF lithography. After KrF lithography, polyacrylate-based resists have been developed for ArF lithography and used in sub-60 nm fabrication. Both types of resist are candidate platforms of extreme ultraviolet (EUV) resists. In this study, the acid generation mechanisms induced by EUV radiation in both types of resist were investigated from the viewpoint of the deprotonation of polymer radical cations using poly(4-hydroxystyrene), poly(methyl methacrylate), and poly(methyl methacrylate-co-4-hydroxystyrene) as model polymers. The dependence of the quantum efficiencies on the molecular structures and acid generator concentration indicated that the deprotonation mechanisms induced by EUV radiation is the same as those induced using an electron beam.

Qualitative gas temperature distribution in positive DC glow corona using spectral image processing in atmospheric air

An experimental method of determining a qualitative two-dimensional image of the gas temperature in stationary atmospheric nonthermal plasma by spectral image processing was presented. In the experiment, a steady-state glow corona discharge was generated by applying a positive DC voltage to a rod-plane electrode in synthetic air. The changes in the gas temperature distribution due to the amplitude of applied voltage and the ambient gas pressure were investigated. Spectral images of a positive DC glow corona were taken using a gated ICCD camera with ultranarrow band-pass filters, corresponding to the head and tail of a N2 second positive system band (0–2). The qualitative gas temperature was obtained from the emission intensity ratio between the head and tail of the N2 second positive system band (0–2). From the results, we confirmed that the gas temperature and its distribution of a positive DC glow corona increased with increasing applied voltage. In particular, just before the sparkover voltage, a distinctly high temperature region was formed in the positive DC glow at the tip of the rod electrode. In addition, the gas temperature decreased and its distribution spread diffusely with decreasing ambient gas pressure.

Performance comparison of chemically amplified resists under EUV, EB and KrF exposure

EUV exposure is crucial to evaluate EUV resists but there are currently a limited number of EUV exposure tools available worldwide. Therefore, an alternative exposure method should be considered to accelerate EUV resist development. To design materials for EUV resist, it is useful to identify and characterize acid generation mechanisms under EUV exposure. To do this, a performance comparison under EUV, EB and KrF exposure was performed to gather information about the acid generation mechanism during EUV exposure. In this paper, the performance of chemically amplified resists under EUV, EB and KrF was compared regarding sensitivity, LWR and pattern-profile not only to consider alternative exposure methods but also to elucidate the acid generation mechanism under EUV exposure. Regarding sensitivity, good correlation was observed between EUV and EB exposure, however, in regard to LWR and resist pattern profile, poor correlation was observed between EUV and EB exposure, and between EUV and KrF exposure. As a result, alternative exposure methods could be used only for basic evaluation and it was determined that EUV exposure was necessary for EUV resist development using chemically amplified resist. From the correlation of sensitivity between EUV and EB exposure, it is suggested that the main acid generation mechanism under EUV exposure was ionization.

Electron swarm parameters in gas mixtures of CF 3 I, SF 6 , CO 2 with N 2 at atmospheric pressure

This paper presents the insulation characteristics of gas mixture containing CF3I as an alternative to SF6 from the view point of electron swarm parameters. The electron swarm parameters including electron attachment and multiplication, electron drift velocity and the effective ionization coefficient were investigated both experimentally and numerically in gas mixtures of CF3I, SF6, CO2 with N2 at atmospheric pressure. In the experiment, weakly-ionized plasma was generated between a quasi-uniform field gap by pulse laser irradiation in test gas, and the electron drift velocity and the effective ionization coefficient were estimated from the electron current waveforms at various electric field strength. In addition, the measured results were compared with numerical results calculated by means of Monte Carlo Simulation. As a result, the measured result of electron drift velocity was in good agreement with calculated one. It was revealed that dilute CF3I in N2 had a strong electron attachment effect as well or better to dilute SF6 in N2 at atmospheric pressure.