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

本研究的目的是建立大直径透镜（材料：CaF2，直径：Φ 200mm）对波长：193nm的紫外线的高精度透射率测量技术（精度：0.01%）。提出了利用光声光谱法测量透光率的方法。该技术仅依赖于局部微小区域的光热光谱，与透镜尺寸无关。因此，该方法适用于大直径透镜。而且某一点的测量时间非常短。因此，该方法的优点是可以方便地测量平面内的透射率分布。实验证明，该光声光谱法适用于大口径透镜。在高光子能量准分子激光（ArF）测量CaF2透射率的情况下，观察到光能的吸收现象与残余应力相关。在本报告中，我们将光吸收建模为光活度，并通过实验验证了该模型，通过应变试验机（senarmont法）测量了双折射，并通过二色性模型表示了光吸收能量的量。

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.