Noriaki Shimodaira

Raman spectra of fluorine-doped silica glasses with various fictive temperatures

We have demonstrated the change of the Raman spectra in F-doped silica glasses with various fictive temperatures, and have also presented a useful peak-deconvolution technique for evaluating the relative concentration of D1 and D2 bands that could be attributed to four- and three-membered ring structures. The intensities of D1 and D2 bands are mainly dominated by the fictive temperature, and they are not almost affected by the F content at the same fictive temperature. It has been made clear that the intensity of D1 band as well as D2 band has a linear relationship with the IR peak position around 2260 cm−1 that is correlated with the average Si–O–Si bond angle, irrespective of the F content. The “activation energies” of D1 and D2, estimated from the Arrhenius plot, are 0.26 and 0.41 eV, respectively.

Refractive index and density in F- and Cl-doped silica glasses

The refractive index and density of fluorine- and chlorine-doped silica glasses were measured as functions of fictive temperature. The halogen concentrations were observed to have a refractive index or density that is independent of the fictive temperature were found. This implies that these properties are not affected by any heat-treatment conditions.

VUV transmittance of fused silica glass influenced by thermal disorder

The technological development of projection photolithography at the 157 nm wavelength of the F2 laser followed by the 193 nm of the ArF excimer laser has been progressing rapidly. Fused silica glass is most promising candidate for 157 nm photomasks, while its absorption edge is extremely close to 157 nm. In this paper the vacuum,-UV transmittance curve at temperatures of 298 to 498 K was examined. The curve gradually shift to longer wavelengths due to thermal disorder and the transmittance at 157nm decreased with increasing temperature. The rise in temperature induced by F2 laser energy density and the irradiation time. For examples, in the case of 0.9 internal transmittance and a fluence of 0.1 mJ/cm(superscript 2/pulse with 1 kHz frequency, the temperature raised by about 8K. The change of transmittance at 157 nm accompanying the increment of 8K is negligibly small. The data suggests that the transmission loss caused by thermal disorder during F2 laser irradiation can be neglected as long as the silica glass with high internal transmittance is used in 157 nm photomasks.