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相移点衍射干涉仪(PS/PDI)是应用于极紫外光刻投影物镜波像差在线检测的高精度检测设备。在介绍国际相关机构PS/PDI研究进展的基础上,重点阐述在干涉仪优化设计、高精度对准、系统误差标定以及干涉图像处理等PS/PDI关键技术研究方面取得的成果。以关键技术研究为基础,开发了一套可见光波段的PS/PDI原理实验装置,并利用该装置检测了极紫外光刻中典型的Schwarzschild投影物镜的波像差,自主开发的20倍缩小Schwarzschild物镜的数值孔径达到了0.2。实验结果表明,干涉仪的重复对准精度优于0.1μm,波像差的绝对检测精度均方根(RMS)误差达到了0.025λ(λ为检查光波长),重复检测精度RMS优于0.001λ,检测速度达到了20秒/视场点。
Phase-shift point diffraction interferometer (PS / PDI) is a high-precision detection device used in online detection of wave aberration of EUV lithography objective lens. Based on the research progress of PS / PDI in related international agencies, this paper mainly elaborates the achievements in the key PS / PDI technologies such as interferometer optimization design, high precision alignment, system error calibration and interference image processing. Based on the key technologies, a set of PS / PDI experimental apparatus in the visible light band was developed. The wavefront aberration of typical Schwarzschild projection objective in EUV lithography was detected by this device. The self-developed 20x Schwarzschild objective lens The numerical aperture reached 0.2. Experimental results show that the repeatability of the interferometer is better than 0.1μm, RMS error of the absolute detection accuracy of the wave aberration reaches 0.025λ (λ is the wavelength of the inspection light), and the RMS of repeatability is better than 0.001λ , Detection speed reached 20 seconds / field of view.