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针对精密反射镜的重力变形,提出了一种基于径向预紧力的变形补偿方法。以高数值孔径(NA)投影光刻物镜中的反射镜为研究对象,建立了反射镜的受力模型,定性分析了径向预紧力对反射镜重力变形的影响规律。利用有限元分析方法得到了在不同径向预紧力作用下反射镜的面形变化,通过数据拟合分析了径向预紧力与面形误差及其泽尼克系数之间的关系。分析结果表明:径向预紧力主要影响反射镜面形的球差项和三叶像差项;随着径向预紧力的增大,补偿后的面形误差呈现先减小后增大的趋势,当径向预紧力约为25 N时,由于重力导致的面形误差由2.009 nm减小为0.462 nm,补偿结果最优。通过实验测量了重力和预紧力作用下反射镜的面形误差,当径向预紧力为25 N时重力导致的反射镜面形误差减小了0.988 nm,从而验证了分析过程和补偿方法的正确性。
Aiming at the gravity deformation of precision mirror, a method of deformation compensation based on radial preload force is proposed. Taking high numerical aperture (NA) projection mirrors as the mirror, the force model of the mirror was established and the influence of the radial preload on the gravity deformation of the mirror was analyzed qualitatively. The surface shape of the mirror under different radial pretension is obtained by finite element analysis. The relationship between the radial pretension force and the surface error and its Zernike coefficient is analyzed by data fitting. The results show that the radial pretension mainly affects the spherical aberration and the trilobal aberration of the mirror surface. With the increase of the radial pretensioning force, the surface error after compensation decreases first and then increases The trend is that when the radial pretension is about 25 N, the compensation result is the best when the area error due to gravity decreases from 2.009 nm to 0.462 nm. The surface error of the mirror under the action of gravity and preload is measured experimentally. When the radial pretensioning force is 25 N, the mirror error caused by gravity decreases by 0.988 nm, which verifies that the analysis process and the compensation method Correctness