扫描干涉光刻中干涉条纹漂移误差分析及抑制

发布时间：2018-09-05 07:27

【摘要】：大面积高精度平面光栅在高端光刻机工件台、惯性约束核聚变以及大型天文望远镜等重大民生及国防科学领域具有不可替代的作用,国家的诸多重大工程建设项目对这类光栅有着非常迫切的需求。然而由于技术与产品禁运,我国不得不自行研制生产这类高技术难度的平面光栅。目前平面光栅的制作方法中,MIT的Schattenburg课题组所采用的扫描干涉光刻法制作出的光栅面积最大,同时精度也非常高。该技术利用工件台承载基底相对于直径仅为2mm左右的曝光图像做步进扫描运动实现大口径光栅的制造。该技术的核心在于通过相关的图像锁定技术抑制曝光图像上干涉条纹相对于曝光基底的漂移,而从形成方式上区分,条纹漂移又可分为干涉条纹自身的漂移以及曝光图像整体相对于曝光基底的漂移。在光刻系统中如何降低上述条纹漂移误差是提高曝光光栅图像精度的关键,这将直接影响成品光栅的各项精度指标。本文围绕清华大学王磊杰提出的基于零差图像锁定技术制作光栅的扫描干涉光刻系统方案,把对光刻精度影响最大的干涉图像条纹漂移误差分为三种类型,并由此展开,详细分析了相位测量框架、光栅位移测量干涉仪模块以及工件台刚体运动引入的测量误差以及由此间接对条纹稳定性造成的影响,给出了必须在扫描干涉光刻机设计中予以重视的相关测量误差。此外,以现有零差图像锁定验证实验装置为分析对象,对扫描干涉光刻中的相关光学元件的高频振动直接引起的条纹漂移误差进行了分析,得到了光学元件振动与条纹漂移间的传递关系,同时分析得出系统设计中应该避免并且会引入高频条纹漂移误差的结构弱点。最后以条纹漂移误差分析为基础,建立了一套在扫描干涉光刻机中抑制条纹漂移误差的整体优化设计方案,包括对刚体运动引起的测量误差以及反馈控制难以抑制的高频条纹漂移误差的抑制。并且对关键优化方法设计了相应的单元实验验证方案,实验结果显示,因测量光栅相对于光栅干涉仪刚体偏转引起的测量误差大幅下降,同时零差图像锁定误差从未优化前的46.1mrad(3σ)下降到了6.5mrad(3σ)。以上结果均很好的验证了文中所提出的优化方案的可行性,为今后的扫描干涉光刻机实际设计提供了切实有效的条纹漂移误差抑制思路。
[Abstract]:Large area and high precision plane gratings play an irreplaceable role in the fields of high end lithography workpiece, inertial confinement fusion, large astronomical telescope and other important fields of people's livelihood and national defense science. There is an urgent need for this kind of grating in many major national engineering projects. However, due to the embargo of technology and products, China has to develop and produce this kind of high-tech plane gratings. At present, the scanning interference lithography method used by the Schattenburg team of Schattenburg is the largest in the fabrication of plane grating, and the precision is very high. In this technique, the large aperture grating can be fabricated by the step scanning motion of the workpiece bearing substrate relative to the exposure image whose diameter is only about 2mm. The core of this technique is to suppress the drift of interference fringes relative to the exposure substrate through the relevant image locking technique, and to distinguish the pattern of the interference fringes from the exposure substrate. The fringes drift can be divided into the drift of interference fringes and the drift of the whole exposure image relative to the exposure substrate. In the lithography system, how to reduce the fringe drift error is the key to improve the precision of the exposure grating image, which will directly affect the precision of the finished grating. In this paper, the scanning interference lithography system based on the homodyne image locking technique proposed by Wang Gupta of Tsinghua University is proposed. The fringe drift error of the interference image, which has the greatest influence on the lithography accuracy, is divided into three types, and it is expanded. The measurement errors caused by the phase measurement frame, the interferometer module of grating displacement measurement and the rigid body motion of the workpiece are analyzed in detail, as well as the indirect influence on the stability of the fringes. The relative measurement errors which must be paid attention to in the design of scanning interference lithography machine are given. In addition, the fringe drift error caused by high frequency vibration of relative optical elements in scanning interferometry lithography is analyzed by using the existing lock-in verification device of homodyne image as the object of analysis. The transfer relationship between vibration and stripe drift of optical elements is obtained, and the structural weakness that high frequency fringe drift error should be avoided and will be introduced in the system design is analyzed. Finally, based on the analysis of the fringe drift error, a set of overall optimum design scheme for restraining the fringe drift error in the scanning interference lithography is established. Including the measurement error caused by rigid body motion and the high frequency fringe drift error which is difficult to be suppressed by feedback control. The experimental results show that the measurement error caused by the deflection of the grating relative to the rigid body of the grating interferometer is greatly reduced. At the same time, the lock-in error of homodyne image has never been reduced from 46.1mrad (3 蟽) to 6.5mrad (3 蟽) before optimization. The above results all verify the feasibility of the proposed optimization scheme and provide a practical and effective way to suppress the fringe drift error for the practical design of the scanning interference lithography machine in the future.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN305.7

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