| 题名 | 光刻投影物镜波像差原位干涉检测技术研究 |
| 作者 | 吴飞斌 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 唐锋 |
| 关键词 | 光刻投影物镜 1xnm节点 波像差原位检测 Ronchi剪切干涉仪 相位提取 |
| 其他题名 | Study on In-situ Interferometric Wavefront Aberration Measurement Techniques for Lithography Projection Lens |
| 中文摘要 | 光刻技术是极大规模集成电路制造的核心技术，光刻机是光刻工艺中的关键设备，决定了集成电路的特征尺寸。投影物镜是光刻机系统的核心部件，其成像质量决定了光刻分辨率和套刻精度。波像差是评价光刻投影物镜成像质量的重要参数；随着193nm浸液式光刻机延伸至1x nm以下技术节点，高端光刻机投影物镜的波像差已达到1nm RMS以下；并且光刻机产率已达到250wph，投影物镜热像差更加显著；为了准确控制光刻投影物镜波像差，需要进行高速、高精度原位波像差检测。 干涉检测技术是目前检测精度最高的波像差检测技术。面向高端光刻机投影物镜波像差原位检测，研究Ronchi剪切干涉仪的工作原理、干涉场表达式、相位提取算法及其相位提取误差，并进行实验系统设计及实验验证。主要工作总结如下： 1．研究了Ronchi剪切干涉技术的工作原理及干涉场表达式。在被测投影物镜物平面和像平面分别放置Ronchi光栅和棋盘光栅，物面Ronchi光栅对光场空间相干性进行调制，像面棋盘光栅对光束进行剪切，通过沿剪切方向移动像面光栅实现相移；与传统的横向剪切干涉仪相比，Ronchi剪切干涉仪具备共光路、零条纹检测、不存在载波和空间光程误差等优点，且用于光刻机波像差原位检测时，不明显增加额外硬件、检测速度快、精度高。基于光栅衍射和范西特-泽尼克空间相干性理论推导了Ronchi剪切干涉场的表达式。 2．提出了两种新的可消除多级衍射光寄生干涉影响的Ronchi剪切干涉仪相位提取算法。针对Ronchi剪切干涉仪光栅同时存在多级衍射寄生干涉影响波前相位提取，提出了八步和十步相移算法，分别消除±5级和±9级以内衍射寄生干涉的影响，理论相位提取误差RMS值分别达到4.4mλ和1.9mλ。 3．系统研究了影响Ronchi剪切干涉仪相位提取精度的主要因素。对相移误差、探测器响应非线性、振动、光栅制造工艺误差和光源空间相干性等误差源的对相位提取误差的影响进行定量分析，对比了不同相移算法下Ronchi相移剪切干涉仪的相位提取精度。开展了采用不同的相移算法、剪切率和光源空间相干性的三组对比实验，实验数据验证了理论推导的正确性和相位提取算法的有效性。基于相位提取精度需求，提出了高精度Ronchi剪切干涉仪的系统参数需求：高精度Ronchi剪切干涉仪系统应满足相移误差优于2%；探测器位数大于10位；光栅周期误差小于1%；光源空间相干性低于0.1。 4．基于上述分析，针对面向1x nm节点的光刻投影物镜原位检测需求，开展了用于193nm光刻机投影物镜波像差检测的Ronchi剪切干涉仪系统参数设计。 5．建立了Ronchi剪切干涉投影物镜波像差检测实验系统。光源采用432nm的LED光源，被测物镜是成像放大倍数为10:1、数值孔径为0.25的标准显微物镜，物面光栅是周期为117.4μm的Ronchi光栅，像面光栅是周期为11.74μm的棋盘光栅，采用所提出的相移算法对所采集的干涉图进行计算，求出x方向和y方向的剪切波前相位，采用差分Zernike波前重建算进行波前重建，得到被测物镜波像差为77.01nm PV，16.43nm RMS。 |
| 英文摘要 | Optical lithography is the key technology in the manufacturing of ultra-large scale integrated circuits. As the key equipment in the lithography process, the lithography tools determine the critical dimension of the integrated circuits. The projection lens is the core component of a lithography tool. Its performances can determine the resolution and overlay of the lithography tool. Wavefront aberration is a significant parameter for evaluating the lithography imaging quality. Combined with the Multiple Patterning, Directed Self Assembly and so on, state-of-the-art immersion lithography is extended down to 1x nm production nodes. The wavefront aberration of advanced lithography projection lens is better than 1 nm RMS. With the critical dimension uniformity and overlay become tighter and the requirements for throughput become higher, the thermal aberration caused by lens heating cannot be neglected. In order to meet the requirements for the performance improvements of lithographic tools, the lithography imaging quality must be guaranteed. So in-situ wavefront aberration measurement techniques with high speed and accuracy must be developed. Interferometric measurement techniques have the highest measurement accuracy of current wavefront aberration measurement techniques. In this dissertation, the work principles, interference model, phase retrieval algorithms and errors of Ronchi shearing interferometer are studied for in-situ interferometric wavefront aberration measurement for advanced lithography projection lens.The main contents are as follows: 1.The work principles and interference model of Ronchi shearing interferometer are studied. A Ronchi grating is placed at the object plane of the projection lens under test to modulate the spatial coherence of light field. A chessboard grating is placed at the image plane of the projection lens under test to split the wavefront into overlapping diffraction orders that generates the sheared interferogram. Phase shifting can be brought by laterally moving the image plane grating. Compared with the traditional lateral shearing interferometer, the Ronchi shearing interferometer has the advantages of simple structure, common-path, null-fringe detection and so on. With the advantages of high detection speed and accuray without installing additional optics, the Ronchi shearing interferometer can be used for in-situ aberration measurement of lithography projection lens. The interference model of Ronchi shearing interferometer is derived by theories of grating diffraction and spatial coherence. 2.Two novel phase-shifting algorithms are proposed to eliminate negative effects of unwanted interference from the high order diffraction light, which limits the accuracy of phase retrieval. Two phase extraction algorithms with eight and ten phase steps repectivelly are proposed to eliminate negative effects of unwanted interference from the high order diffraction light. The negtive influence of the first ±5 and the first ±9 orders diffractions on phase extraction can be eliminated by the eight-frame and ten-frame algorithm respectively. Their theoretical phase calculation errors are 4.4mλ and 1.9mλ (RMS) respectively. 3.The main error sources of the Ronchi interferometer are systematically studied. The effects on phase extraction accuracy are quantitative analyzed, including phase-shift non-linearity, detector non-linearity and quantization, vibration, grating manufacturing and period errors, the spatial coherence error and so on. The measurement accuracy of different phase-shifting algorithms are compared. The theoretical analysis is validated by three groups of comparison experiments with different phase extraction algorithms, shear ratios and spatial coherence of light. In order to meet the phase retrieval accuracy requirements, the following system parameters should be satisfied: the phase shifting error should be less than 2%, at least 10-bit quantization detector should be used, the grating period error and the spatial coherence of light should be less than 1% and 0.1 respectively. 4.Based on the requirements of in situ wavefront aberration measurement for 1x nm node lithography projection lens, typical system parameters of Ronchi shearing interferometer are designed for 193nm lithography projection lens wavefront aberration measurement. 5.A lithography lens wavefront aberration measurement system based on Ronchi shearing interferometry is built. In this system, a LED array light (λ=432nm) is used as the exposure source. A strandard microobjective with a 10:1 magnification factor and 0.35 numerical aperture is used as the tested projection lens. A Ronchi grating (period=117.4μm) and a chessboard grating (period=11.74μm) are used as the object grating and the image grating respectively. The x- and y- direction phase of the tested wavefront can be calculated from the shearing interferograms by using the proposed phase extraction algorithms. With the differential Zernike wavefront reconstruction algorithms, the tested wavefront can be reconstructed and the calculation aberration results are 77.01nm (PV) and 16.43nm (RMS) |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16900]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 吴飞斌. 光刻投影物镜波像差原位干涉检测技术研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
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