超高精度非球面面形检测技术研究

	超高精度非球面面形检测技术研究
	高松涛
学位类型	博士
导师	杨怀江
	2014-07
学位授予单位	中国科学院大学
学位专业	光学
摘要	光学设计中，单个球面可以供优化的自由度只有曲率半径；而非球面除了顶点曲率半径之外，还有二次曲面常数和高阶项系数。由于非球面比球面拥有更多设计自由度，所以在高NA投影光刻物镜中，都普遍采用非球面元件来减小系统的复杂度，并提高系统的成像质量。虽然非球面有优良的光学性质，但是非球面检测，特别是超高精度非球面面形检测，一直是光学检测领域的一个难题，也是制约非球面元件应用的关键因素。对于非球面偏离度较小的非球面，可以采用环带拼接法或子孔径拼接法进行检测，但检测精度往往受制于机械定位误差和干涉仪的非共光路误差。如果非球面是二次曲面，也可以采用无像差点法进行检测，但往往会引入中心遮拦；而高次非球面，则采用零位补偿法进行检测。对于高NA投影光刻物镜而言，非球面度往往比较大，并且对面形精度要求极为苛刻(RMS为亚纳米量级)，对于如此高精度的非球面，一般只能采用零位补偿法进行检测。针对高NA投影光刻物镜对超高精度非球面面形检测的需要，本论文以计算全息图(Computer-Generated Hologram, CGH)和补偿镜为零位补偿器，主要开展了以下研究内容：1、CGH设计。分析了CGH的工作原理、工作模式和衍射效率，给出了CGH相位和空间频率的计算方法；针对高NA投影光刻物镜中的一高次偶次非球面，详细论述了零位补偿CGH和辅助调节CGH的设计方法，并重点分析了衍射鬼像的产生机理和剔除方法；基于Matlab软件平台，利用论文所论述的方法，编写了CGH设计软件，利用该软件实现对光刻物镜中的非球面所需CGH的设计。2、用CGH对非球面检测的误差分析及标定方法。系统分析了CGH的基底误差、CGH的刻蚀误差、CGH和非球面的调节误差、CGH的成像畸变和温度压强波动等对非球面检测精度的影响；针对CGH基底误差，给出了基底的标定方法；针对CGH的成像畸变，建立了畸变校正模型，并实现了对CGH成像畸变的高精度校正；针对CGH和非球面的调节误差(球差和彗差)，提出了误差控制的方法；采用非线性最小二乘算法，在测量非球面面形的同时，也实现了对非球面顶点曲率半径的高精度测量。同时，考虑到整个系统的轴对称性，采用多角度平均的方法，实现了对非球面旋转非对称面形的绝对标定，进一步提高了非球面的检测精度。3、高精度补偿镜的设计及公差分配。论文提出采用平行光入射的补偿镜设计方案，与其他设计方法相比，该设计方案便于调节(不用调节补偿镜的轴向距离和偏心)，避免了补偿镜的调节误差对非球面测量精度的影响。另外，由于在光学加工和装配过程中采用了“光学复算”的方法，在满足非球面检测精度的情况下，使补偿镜的曲率半径加工公差、中心厚加工公差和透镜间隔装配公差变的相对宽松，方便补偿镜的加工和装配。4、检测结果的比对和实验验证。针对一抛物面，分别采用无像差点法和CGH法进行了高精度检测；通过对比二者的检测结果，从实验上验证了CGH法的准确性。
其他摘要	Sphere has only one radius of curvature (ROC) as a freedom to optimize in the optical design process. However, asphere has conic constant and high order coefficients besides the vertex radius of curvature (VROC) to optimize. Because the asphere owns more designing freedoms, aspheres are commonly used in the high-NA projection objectives to decrease the complexity and improve the imaging performance. Although asphere owns many optical advantages, the testing of asphere, especially the ultra-precise testing of asphere, is a challenge for optical testing. At the same time, it is the key factor to restrict the application of asphere. If the asphere departure from the best-fitting sphere is small, the asphere could be tested by annular stitching or sub-aperture stitching, but the testing precision is restricted by the mechanical position error and the retrace error of interferometer. If the asphere is conic surface, it could be tested by stigmatic null test, but the center of the testing asphere is usually obscured. If the asphere is general high order asphere, it could be tested by compensating null test. For the aspheres in the high-NA projection objectives, because the asphere departure is very large and the testing precision is very critical (RMS less than 1nm), maybe the compensating null test is the only choice.For the asphere testing requirements of high-NA projection objective, this dissertation uses Computer-Generated Hologram (CGH) and null lens as complementor carrying researches as below:1.The design of high precise CGH. The thesis analyses the CGH working principle, CGH working modes and diffraction efficiency, gives the calculating methods of CGH phase and CGH spatial frequency. For a general high order asphere of high-NA projection objectives, the thesis discusses the designing method of Null CGH and Alignment CGH in detail, and analyses the reason how the diffracting ghosts turn up, and gives method to avoid them. Using the methods described in this thesis a program based on Matlab platform is compiled to complete the CGHs design for the aspheres in the high-NA projection objective.2.The error analysis for asphere testing with CGH and calibration methods. The thesis analyses the substrate error, etching error, alignment error of CGH and asphere, imaging distortion and the influence of temperature and pressure fluctuation. For the substrate error of CGH, the thesis gives the calibration methods. For the imaging distortion of CGH, a model is built to complete the distortion correcting precisely. For the alignment errors of testing (spherical aberration and coma), an effective method is given to restrict these errors. Using the nonlinear least-square method, the VROC is acquired when measuring the aspheric surface. At the same time, considering the rotational symmetry of asphere, the rotational asymmetric surface could be calibrated absolutely using the multi-angle averaging method to improve the testing precision.3.The designing and tolerancing of high precise null lens. Compared to other designs, the design using the parallel beam illuminating the null lens could be easily aligned (need not to take the axial alignment and decenter alignment) and avoid the alignment errors for asphere testing. Furthermore, the null lens fabricating tolerance of ROC and center thickness, and the aligning tolerance of spacing will be much loosened for using the optical redesign method in the fabricating and aligning process. This will be very favorable for optical fabrication and alignment.4.The results comparing and experimental verification. A paraboloid is tested precisely using stigmatic null test and CGH null test respectively. The precision of CGH is verified experimentally through comparing the two testing results.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/41407
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	高松涛. 超高精度非球面面形检测技术研究[D]. 中国科学院大学,2014.

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