Study of Ultraviolet Transmittance Measurement by Photoacoustic Method for next generation of Stepper Lens

本研究旨在建立大口径透镜（材料：CaF2，直径：Φ 200 mm）对紫外线（波长：193 nm）透过率的高精度测量技术（精度：0.01%）。提出了光声光谱法测量透射率的方法。该技术仅依赖于局部微小区域的光热光谱，并且与透镜尺寸无关。该方法可应用于大口径透镜。而且在一个点上的测量时间非常短。因此，该方法的优点在于可以方便地测量面内透射率分布。实验验证了该光声光谱法可用于大口径透镜的测量，在利用高光子能量的准分子激光（ArF）测量CaF 2透过率的情况下，观察到了与残余应力相关的光能吸收现象。在本报告中，我们建立了一个光学吸收的旋光性模型，我们验证了这个模型，双折射测量的应变测试机（塞纳蒙特方法），光吸收能量的量由二向色性模型制定。

The purpose of this study is establishment of the high precision transmittance measurement technology (accuracy : 0.01%) of the large diameter lens(material : CaF2, diameter : Φ 200mm) for ultraviolet rays (wavelength : 193nm). Transmittance measurement method with photoacoustic spectroscopy is proposed. This technology depends on only photothermal spectroscopy at a local minute area and is independent of lens size. So this proposed method can be applied to large diameter lens. And measurement time at one point is extremely short. So the superiority of this new method is that the transmittance distribution in-plane can be easily measured. It was experimentally verified that this photoacoustic spectroscopy could be applicable to large diameter lens.In the case of transmittance measurement of CaF2 by the excimer laser(ArF) which has high photon energy, the absorption phenomenon of the light energy which is correlated with the residual stress was observed. In this report, we modeled an optical absorption as optical activity, and we verified this model experimentally, the double refraction was measured by strain testing machine (the senarmont method), and the amount of light absorption energy is formulated by dichroism model.