Mr. Yasuo Itakura Profile

Yasuo Itakura

Researcher at Komatsu Ltd

SPIE Involvement:

Author

Publications (13)

Proceedings Article | 12 May 2005 Paper

Development and evaluation of an F2 laser for immersion interference lithography at 157nm

Yasuo Itakura, Youichi Kawasa, Osamu Wakabayashi, Masato Moriya, Shinji Nagai, Akira Sumitani, Takuya Hagiwara, Toshiyuki Ishimaru, Shou Tsuji, Kiyoshi Fujii, Wataru Wakamiya

Proceedings Volume 5754, (2005) https://doi.org/10.1117/12.599512

KEYWORDS: Polarization, Interferometers, Lithography, Fluorine, Spatial coherence, Prisms, Immersion lithography, Fringe analysis, Laser resonators, Visibility

Read Abstract +

Proceedings Article | 12 May 2005 Paper

Liquid immersion lithography at 157 nm

Takuya Hagiwara, Toshiyuki Ishimaru, Shou Tsuji, Kiyoshi Fujii, Yasuo Itakura, Osamu Wakabayashi, Youichi Kawasa, Keiji Egawa, Ikuo Uchino, Akira Sumitani, Yusuke Saito, Kazuhiko Maeda

Proceedings Volume 5754, (2005) https://doi.org/10.1117/12.599379

KEYWORDS: Absorption, Transparency, Interferometry, Immersion lithography, Chemical species, Microfluidics, Refractive index, Fluorine, Semiconducting wafers, Glasses

Read Abstract +

Proceedings Article | 28 May 2004 Paper

Evaluation systems of F2 laser lithography materials

Yasuo Itakura, Youichi Kawasa, Keiji Egawa, Akira Sumitani, Hironao Sasaki, Iwao Higasikawa, Shigeo Irie, Kiyoshi Fujii, Toshiro Itani, Hitoshi Nakano, Hideo Hata

Proceedings Volume 5377, (2004) https://doi.org/10.1117/12.534839

KEYWORDS: Transmittance, Pellicles, Photomasks, Fluorine, Lithography, Laser irradiation, Semiconducting wafers, Vacuum ultraviolet, Contamination, Laser development

Read Abstract +

Proceedings Article | 14 May 2004 Paper

Evaluation of outgassing from a fluorinated resist for 157-nm lithography

Shigeo Irie, Kiyoshi Fujii, Yasuo Itakura, Youichi Kawasa , Keiji Egawa, Ikuo Uchino, Akira Sumitani, Toshiro Itani

Proceedings Volume 5376, (2004) https://doi.org/10.1117/12.535110

KEYWORDS: Absorption, Transmittance, Ions, Polymers, Transmission electron microscopy, Lithography, Natural surfaces, Optical components, Contamination, Chemical analysis

Read Abstract +

We have evaluated the outgassing products and the in-situ transmittance of a contaminated CaF₂ substrate for monocyclic fluoropolymers with four protecting groups: methoxymethyl (MOM), tert-butoxycarbonyl (t-BOC), menthoxymethyl (MM), and 2-cyclohexylcyclohexyloxymethyl (CCOM). We have also evaluated the same type of fluoropolymer with seven kinds of photo-acid generators (PAGs) added to a base fluoropolymer solution. We found little correlation between the total amount of outgassing from the polymer and the decreasing rate of the CaF₂ substrate transmittance caused by outgassing adhesion. Although the MOM protecting group generated the largest amount of outgassing products, the most substantial decrease in the transmittance was observed for the t-BOC protecting group. Also, the outgassing products due to use of a PAG did not greatly reduce the absorption coefficient of a CaF₂ substrate regardless of the kind of PAG. Therefore, the absorption coefficient of the outgassing-contaminated CaF₂ substrate appears to be more sensitive to the type of protecting group, especially the t-BOC protecting group including a t-butyl unit, rather than the type of fluoropolymer or PAG. We analyzed the substrate surface contaminant due to the t-butyl unit by x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS), and found that increasing amounts of organic compounds, containing mainly C- and H-atoms, were adhered to and deposited on the substrate surface with an increasing irradiation dose. We speculate that the contaminants on a CaF₂ surface with or without an anti-reflective coating were formed not only through mere physical adsorption, but also through certain chemical combinations. We conclude that in terms of material design of the fluoropolymer resist for 157-nm lithography, we need to pay attention to the protecting group of polymers, especially the t-BOC or t-butyl protecting group, which generates isobutene product during 157-nm irradiation.

Proceedings Article | 12 June 2003 Paper

Study of resist outgassing by F2 laser irradiation

Yasuo Itakura, Youichi Kawasa, Akira Sumitani, Seiichi Ishikawa, Shigeo Irie, Toshiro Itani

Proceedings Volume 5039, (2003) https://doi.org/10.1117/12.485087

KEYWORDS: Fluorine, Contamination, Transmittance, Laser irradiation, Lithography, Absorbance, Semiconducting wafers, Pulsed laser operation, Laser development, Molecules

Read Abstract +

Proceedings Article | 30 July 2002 Paper

In-situ measurements of VUV optical materials for F2 laser

Akira Sumitani, Yasuo Itakura, Fumika Yoshida, Youichi Kawasa, Jing Zhang, Noriyoshi Kanda, Toshiro Itani

Proceedings Volume 4691, (2002) https://doi.org/10.1117/12.474557

KEYWORDS: Transmittance, Vacuum ultraviolet, Laser irradiation, Laser development, Spectrophotometry, Lithography, Silicon, Sensors, Photomasks, Fluorine

Read Abstract +

Proceedings Article | 25 February 2002 Paper

In-situ measurement of VUV optical materials under F2 laser irradiation

Yasuo Itakura, Akira Sumitani, Fumika Yoshida, Youichi Kawasa, Jing Zhang, Osamu Wakabayashi, Hakaru Mizoguchi

Proceedings Volume 4426, (2002) https://doi.org/10.1117/12.456904

KEYWORDS: Transmittance, Laser irradiation, Vacuum ultraviolet, Pulsed laser operation, Laser optics, Spectrophotometry, Reflectivity, Optical coatings, Optical testing, Fluorine

Read Abstract +

Proceedings Article | 14 September 2001 Paper

Evaluation of characteristics of VUV optical materials irradiated by F2 laser

Yasuo Itakura, Fumika Yoshida, Youichi Kawasa, Akira Sumitani, Osamu Wakabayashi, Hakaru Mizoguchi

Proceedings Volume 4346, (2001) https://doi.org/10.1117/12.435641

KEYWORDS: Transmittance, Laser irradiation, Vacuum ultraviolet, Coating, Reflectivity, Spectrophotometry, Surface finishing, Fluorine, Laser optics, Calcium

Read Abstract +

The 157 nm molecular fluorine laser is regarded as the next generation light source for semiconductor exposure technology in the vacuum ultraviolet (VUV) region. Research for high performance F₂ laser optical materials is therefore indispensable. In this paper, we describe methods and results of evaluating optical materials used in the 157 nm region. We have developed an in-situ VUV evaluation system, which can measure the transmittance in the deep ultraviolet (DUV) and the VUV region directly after laser irradiation and the temporal transmittance during 157 nm-laser irradiation without airborne contamination. The system consists of a 2 kHz F₂ laser, an in-situ VUV irradiation system and a specialized VUV spectrophotometer. Laser irradiation and measurements were carried out under high purity nitrogen gas. During the first phase of F₂ laser irradiation (0 approximately 0.7 million pulses), a rapid transmittance increase (87% yields 89%) of calcium fluoride (CaF₂) substrates was observed and this change took almost place within one minute after starting the irradiation. It is assumed that this effect is due to surface cleaning by the F₂ laser beam. Surface polishing has been excluded because the sample surface roughness measured with an atomic force microscope (AFM) showed no difference before and after irradiation. After an irradiation of 0.1 million pulses, the fast initial increase of the transmittance slowed down and finally reached about 89%. The slower increase might be correlated with a reduced chemical bonding of hydroxyl groups on the surface, because the transmittance change at 157 nm was in good agreement with the measured VUV transmittance below 170 nm. This is corresponds with the hydroxyl absorption band below 170 nm. The transmittance and reflectance of high reflection coated substrates were examined as well. Obvious damage and a huge reflectivity loss (82.4% yields 47.4%) were observed after 1.5 billion irradiation pulses. The information obtained during this work is very useful in devising optical F₂ laser components.

Proceedings Article | 6 November 2000 Paper

Evaluation of characteristics of VUV optical materials irradiated by F2 laser

Yasuo Itakura, Fumika Yoshida, Youichi Kawasa, Akira Sumitani, Osamu Wakabayashi, Hakaru Mizoguchi

Proceedings Volume 4088, (2000) https://doi.org/10.1117/12.405748

KEYWORDS: Transmittance, Vacuum ultraviolet, Laser irradiation, Spectrophotometry, Laser optics, Ultraviolet radiation, Calcium, Light sources, Lithography, Laser development

Read Abstract +

Proceedings Article | 6 November 2000 Paper

High-repetition-rate ArF excimer laser for microlithography

Osamu Wakabayashi, Tatsuo Enami, Ken Ishii, Katsutomo Terashima, Yasuo Itakura, Takayuki Watanabe, Takeshi Ohta, Ayako Ohbu, Hirokazu Kubo, Hirokazu Tanaka, Satoshi Andou, Takashi Matsunga, Hiroshi Umeda, Toru Suzuki, Akira Sumitani, Hakaru Mizoguchi

Proceedings Volume 4088, (2000) https://doi.org/10.1117/12.405749

KEYWORDS: Excimer lasers, Gas lasers, Xenon, Laser development, Laser stabilization, Pulsed laser operation, Light sources, Spectroscopy, Laser applications, Lithography

Read Abstract +

Proceedings Article | 5 July 2000 Paper

Highly durable low CoO mass production version of 2-kHz ArF excimer laser for DUV lithography

Tatsuo Enami, Osamu Wakabayashi, Ken Ishii, Katsutomo Terashima, Yasuo Itakura, Takayuki Watanabe, Takeshi Ohta, Ayako Ohbu, Hirokazu Kubo, Hirokazu Tanaka, Toru Suzuki, Akira Sumitani, Hakaru Mizoguchi

Proceedings Volume 4000, (2000) https://doi.org/10.1117/12.388981

KEYWORDS: Excimer lasers, Gas lasers, Laser development, Lithography, Deep ultraviolet, Performance modeling, Electrodes, Optical lithography, Light sources, Laser applications

Read Abstract +

Proceedings Article | 7 July 1997 Paper

Subpicometer ArF excimer laser for 193-nm lithography

Jun Akita, Hiroshi Komori, Noriaki Kouda, Shunsuke Yoshioka, Yasuo Itakura, Hakaru Mizoguchi

Proceedings Volume 3051, (1997) https://doi.org/10.1117/12.276010

KEYWORDS: Excimer lasers, Lithography, Laser development, Argon ion lasers, Lenses, Laser stabilization, Optical lithography

Read Abstract +

Proceedings Article | 7 June 1996 Paper

High-power KrF excimer laser with a solid state switch for microlithography

Hakaru Mizoguchi, Noritoshi Ito, Hiroaki Nakarai, Yukio Kobayashi, Yasuo Itakura, Hiroshi Komori, Osamu Wakabayashi, Taketo Aruga, Takashi Sakugawa, Takehisa Koganezawa

Proceedings Volume 2726, (1996) https://doi.org/10.1117/12.240945

KEYWORDS: Excimer lasers, Solid state lasers, Pulsed power, Chlorine, Solid state physics, Switches, Pulsed laser operation, Optical lithography, Reliability, Switching

Read Abstract +

Showing 5 of 13 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years