30 July 2002 In-situ measurements of VUV optical materials for F2 laser
Author Affiliations +
F2 laser lithography (wavelength:157 nm) is a candidate of post-ArF excimer laser lithography. In order to test the characteristics of vacuum ultraviolet (VUV) materials for F2 laser lithography, we developed an evaluation system consisting of a 1 kHz F2 laser, an in-situ real-time transmittance measurement unit and an in-situ VUV spectrophotometer. The precision of the real-time transmittance measurement is +/- 0.5%. The precision of the VUV spectrophotometer measurement is +/- 0.5% for scanned wavelengths (140 - 300 nm) and +/- 0.1% for a constant wavelength (at 157.6 nm). Due to F2 laser irradiation cleaning, the transmittance of uncoated calcium fluoride (CaF2) substrates and of F2 laser coatings at first rapidly and then gradually increased. Thereafter the transmittance remained constant. Results of the real-time transmittance and the VUV spectrophotometer measurement were almost identical. In addition, durability tests of CaF2 substrates and of F2 laser coatings were performed with a 4 kHz F2 laser for more than 10 billion pulses (Bpls). After the initial transmittance increase of CaF2 substrates, no change in transmittance was observed during more than 10 Bpls. In order to maintain the CaF2 substrate transmittance, silicon compounds have to be removed from the purge gas and from the irradiation chamber where optical materials are placed. F2 laser coating quality varied enormously between suppliers.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Akira Sumitani, Yasuo Itakura, Fumika Yoshida, Youichi Kawasa, Jing Zhang, Noriyoshi Kanda, Toshiro Itani, "In-situ measurements of VUV optical materials for F2 laser", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); doi: 10.1117/12.474557; https://doi.org/10.1117/12.474557


Development of bilayered TaSiOx-HTPSM: I
Proceedings of SPIE (September 05 2001)
Materials for an attenuated phase shifting mask in 157 nm...
Proceedings of SPIE (January 22 2001)
Evaluation systems of F2 laser lithography materials
Proceedings of SPIE (May 28 2004)
Fused silica for 157-nm transmittance
Proceedings of SPIE (June 25 1999)

Back to Top