Hiroshi Komano

Photoinduced outgassing from the resist for extreme ultraviolet lithography by the analysis of mass spectroscopy

Extreme ultraviolet lithography (EUVL) requires the vacuum environment for exposing the resist. The contamination in the vacuum environment decreases the reflectivity of the reflective mask and that of the imaging optics. The photoinduced outgassing from the resist becomes the contamination in the vacuum environment. Therefore, the outgassing detection investigation is very important. The outgassing from the chemically amplified (CA) resists EUV001 for EUVL, EUV006N for EUVL, UV5 for KrF lithography and the nonchemically amplified resists OEBR2000 and ZEP520 for electron beam lithography were investigated. Based on the photoinduced reactions of the resist, the fragment ions species that were measured by the quadrupole mass spectrometer were identified. It is found that the amount of the photoinduced outgassing such as hydrocarbons from the DQN resist and annealing-type CA positive-tone resist is small.

Development of fast-photospeed chemically amplified resist in extreme ultraviolet lithography

In a high-annealing type resist system that employs polyhyodroxy styrene as a base resin, we found that tri-phenysulfonium cyclo(1,3-perfluoropropanedisulfone) imidate when employed as a photoacid generator (PAG) is more sensitive than tri-phenysulfonium nonaflate under extreme ultraviolet (EUV) exposure. However, their sensitivities are almost the same under KrF and EB exposures. As results of both outgassing species and FT-IR measurements, the EUV-induced reaction of cyclo(1,3-perfluoropropanedisulfone) imidate employed as an anion of PAG occurred more efficiently than that of nonaflate employed as an anion of PAG. Therefore, the anion of PAG contributes to achieve a fast photospeed under EUV exposure. Furthermore, from the sensitivity curve measurements, it is found that tri-phenylsulfonium employed as a cation increases the developing rate more than diphenyl-naphthylsulfonium employed as a cation of PAG. As a result, we have succeeded in developing a fast photospeed chemically amplified resist that has a sensitivity of 1.1 mJ/cm2 and a partial pressure displacement accumulated in the total exposure time between after and before exposures on the order of 10-6 Pa s.

Resist Outgassing Characteristics in Extreme Ultraviolet Lithography

Extreme ultraviolet (EUV) lithography requires a vacuum environment for exposure. The hydrocarbons outgassing ion species affect the reflectivity of the mask and the imaging mirror under EUV irradiation. Concerning the high-annealing-type chemically amplified (CA) resist based on the polyhydroxy styrene (PHS) resin, it is confirmed that propylene glycol monomethylether (PGME) which is employed as a solvent has the lowest outgassing characteristics under EUV irradiation. Mitigation of the hydrocarbons outgassing species and line edge roughness (LER) requires the main-chain-decomposition-type CA resist. From the outgassing measurement results, the methacrylate base resin can be employed in the resist process in EUV lithography.

Development of fast photospeed chemically amplified resist in EUV lithography

In EUV lithography, the requirement of the resist sensitivity is less than 2 mJ/cm*, which gives the large relaxation to the requirement of the EUV light source power. Furthermore, the line width roughness (LWR) of less than 2 nm (3 sigma) and outgassing total fragment pressure of less than Pa during the exposure time are required. We succeed in developing fast photospeed chemically amplified resist which has the sensitivity of 1.1 mJ/cm2 and partial pressure displacement of in the order of 1 0-6 Pa during the total exposure time. By using novel evaluation system as shown in Fig. 1 for EUVL resist which is simulating 6-imaging-mirror system, the fundamental resist characteristics such as sensitivity curve, outgassing characteristics, and surface roughness, are measured for the chemically amplified resist for EUV lithography. High sensitive quadruple mass spectrometer is utilized for the outgassing ion species from the resist under EUV irradiation. The high-annealing-type chemically amplified (CA) resists based on the polyhydroxy styrene (PHS) resin which employs sulfonium salts as photo-acid generator (PAG) are evaluated. The mitigation of the development for the fast photospeed resist is discussed based on our experimental results. Furthermore, decomposition reaction of PAG under EUV irradiation is discussed based on the results of both outgassing species and FT-IR measurement results.