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题名	基于平面光栅尺的光刻机工件台位置测量技术研究
作者	郑亚忠
文献子类	硕士
导师	步扬
关键词	光刻机，工件台，位置测量，平面光栅尺 Lithography tools, Wafer stage, Position measurement, Plane grating encoder
其他题名	Study on the Position Measurement Technique of Wafer Stage Based on Plane Grating Encoder
英文摘要	集成电路产业是信息技术产业的核心。作为集成电路制造的关键装备，光刻机决定了集成电路的特征尺寸和集成度。工件台系统是光刻机的核心分系统，直接影响光刻机三大性能指标中的产率和套刻精度。其中，光刻机套刻精度受到工件台定位精度的制约，而高精度的工件台位置测量是保证工件台定位精度的先决条件。随着光刻工艺持续向1x nm及以下节点推进，光刻机工件台位置测量精度需求不断提升。 自28nm光刻节点起，光刻机套刻精度要求达到5.7nm以下。以激光波长为测量基准的双频激光干涉技术因测量光程长、易受环境变化影响等缺点，其测量精度已不能满足28nm节点工件台位置测量精度要求。与之相比，平面光栅尺测量技术以光栅栅距为测量基准，具有测量光程短、环境变化敏感性低的优点，理论上其测量精度能够达到亚纳米量级。目前国内基于平面光栅尺的高精度工件台/掩模台位置测量模型尚不完备；对存在栅距误差的平面光栅尺测量系统，如何高精度检测其栅距并进行相应的误差补偿，还缺乏有效的方法。针对上述问题，本文围绕基于平面光栅尺的光刻机工件台位置测量技术开展研究，主要工作有： 1. 建立了基于平面光栅尺的光刻机工件台六自由度测量模型。根据工件台的实际工作状态，设计工件台光栅尺测量系统布局，定义相关坐标系及安装误差，以扫描光程为中间量推导了工件台位置与探测器读数的关系，考虑工件台实际工作过程中可能出现的某一个象限探测器失效的情况，建立全行程范围内工件台六自由度关于激光波长、光栅栅距及安装误差的测量模型。仿真结果表明，采用工件台实际运动速度及运动行程参数，引入与已知设计和装配精度相匹配的安装误差，所建模型的线位移量（X/Y/Z）测量精度优于0.44nm，角位移量（Rx/Ry/Rz）测量精度优于1.36nrad；分别模拟了不同计算频率下的模型测量精度，结果表明在满足工件台位置测量系统实时性要求的条件下，计算频率为5kHz时模型精度更高。 2. 建立了基于平面光栅尺的光刻机掩模台水平向三自由度（X/Y/Rz）测量模型。根据光刻机掩模台的实际工作状态，设计光刻机掩模台光栅尺测量系统布局，以扫描光程为中间量推导了掩模台位置与探测器读数的关系，建立了掩模台水平向三自由度关于激光波长、光栅栅距及安装误差的测量模型。仿真结果表明，在已知掩模台当前时刻Z自由度的情况下，引入与已知设计和装配精度相匹配的安装误差，所建模型线位移量X的测量精度优于1.70nm，Y的测量精度优于0.79nm，角位移量Rz的测量精度优于0.53nrad。 3. 分析了不同类型的光栅栅距误差对光栅尺测量精度的影响。考虑存在局部畸变误差等不同类型栅距误差的光栅尺测量系统，仿真结果表明不同类型的栅距误差均会导致光栅尺测量误差增大，且对光栅尺XOY平面的面内位移测量精度影响远大于垂直于XOY平面的离面位移。为保证光栅尺测量精度，需对存在栅距误差的光栅尺测量系统进行误差补偿，而误差补偿必须以精确的光栅栅距检测结果为基础。为了准确获取光栅尺测量系统中平面光栅的栅距数据，提出了一种基于数字图像相关法的二维光栅栅距检测方法。该方法能够实现光栅栅距的高精度、非接触检测。仿真结果表明，在二维正弦型光栅和二维闪耀光栅栅距检测中，该方法检测精度均优于现有的数字图像周期检测方法。; Integrated circuit (IC) industry is the core of information technology industries. As the key equipment for integrated circuit fabrication, lithography tools determine the critical dimension and the integration level of integrated circuits. Wafer stage system， which is one of the core subsystems in lithography tools, directly affects the throughput and overlay accuracy of lithography tools. The overlay accuracy of lithography tools is restricted by the positioning accuracy of wafer stage, while the high-precision position measurement is a prerequisite for the positioning accuracy of wafer stage. As the lithography process extends to 1x nm technology node and below, the accuracy requirement for position measurement of wafer stage must be improved. For 28nm technology node and below, the overlay accuracy of lithography tools less should be than 5.7nm. The dual-frequency laser interference technique uses laser wavelength as measuring basis. Due to its long measuring beam-length and unstability caused by the measuring environmental change, it cannot meet the accuracy requirement for position measurement of wafer stage. The plane grating encoder measurement technique uses grating pitch as measuring basis. It has short measuring beam-length and it is insensitive to the measuring environmental change. This technique has a theoretical measurement accuracy of sub-nanometer, so it can meet the accuracy requirement for wafer stage’s position measurement. At present, the high-accuracy position measurement model for wafer stage based on plane grating encoder needs to be refined. The technique to detect the pitch error and compensate the pitch error in grating remains to be optimized. In this dissertation, the position measurement technique of wafer stage based on plane grating encoder is studied, the main work are as follows: 1. A six degree of freedom position measuring model for wafer stage based on plane grating encoder is built. According to the actual working state of wafer stage, the layout of encoder measurement system of wafer stage is designed, then the relevant coordinate systems and installation errors is defined. By taking the optical length as intermediate variable, the relationship between position of the wafer stage and the readings of the encoder detectors is modeled. When this system is used to measure the position of wafer stage, the reading of detector in one quadrant may be lost, the model for the six degree of freedom of wafer stage and laser wavelength, grating pitch and installation errors is built through the full stroke. Simulation results show that under the speed of 0.5m/s and moving distance of 500mm, the measurement accuracy of linear displacement (X/Y/Z) is better than 0.44nm, the measurement accuracy of angular displacement (Rx/Ry/Rz) is better than 1.36nrad. The measurement accuracy of model is simulated at different frequencies respectively, simulation results show that the position model with a frequency of 5kHz can measure the position of wafer stage more accurate. 2. A horizontal three degree of freedom position measuring model for reticle stage based on plane grating encoder is built. According to the actual working state of reticle stage, the layout of plane grating encoder measurement system of reticle stage is designed. By taking the optical length as intermediate variable, the relationship between position of reticle stage and the readings of the encoder detectors is modeled. Furthermore, the model for the horizontal three degree of freedom of reticle stage and laser wavelength, grating pitch and installation errors is built. Simulation results show that under the condition of given reticle stage’s real-time Z degree of freedom, the measurement accuracy of linear displacement X is better than 1.70nm, the measurement accuracy of linear displacement Y is better than 0.79nm, the measurement accuracy of angular displacement Rz is better than 0.53nrad. 3. The influence of different types of grating pitch errors on the measurement accuracy of plane grating encoder is analyzed. The plane grating encoder measurement system is simulated with the presence of different types of pitch errors respectively. Simulation results show that different types of pitch errors will increase the measurement error in encoder, and the error of in-plane displacement measurement accuracy increases much more than out-of-plane displacement measurement. In order to ensure the accuracy of the encoder measurement system, the pitch error in encoder measurement system must be compensated, but the error compensation should be based on the accurate pitch evaluation result. Aiming at getting the accurate pitch data of plane grating, a pitch measurement method of two-dimensional gratings based on digital image correlation (DIC) method is proposed, which can detect grating pitch without contact. Simulation results show that the accuracy of DIC method is better than the existing digital image period measurement method in grating pitch detections of two-dimensional sinusoidal grating and two-dimensional blazed grating.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/30978]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	郑亚忠. 基于平面光栅尺的光刻机工件台位置测量技术研究[D].

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