基于深度学习的数字光刻自动检焦方法  

Deep Learning Based Method for Automatic Focus Detection in Digital Lithography

作　　者：杨聚圃 杜佳林 李凡星[1] 谌庆荣 王思沫 严伟[1] YANG Jupu;DU Jialin;LI Fanxing;CHEN Qingrong;WANG Simo;YAN Wei(Institute of Environmental Optics,Institute of Optics and Electronics,Chinese Academy of Sciences,Chengdu 610209,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院光电技术研究所环境光学研究院,成都610209 [2]中国科学院大学,北京100049

出　　处：《光子学报》2022年第6期253-265,共13页Acta Photonica Sinica

基　　金：四川省科技计划项目(Nos.2020JDJQ0007,2021JDRC0089);中科院关键技术团队项目(No.YA20K023);中科院科研仪器设备研制项目(No.YJKYYQ20210041)。

摘　　要：目前基于数字微镜器件的无掩膜光刻系统离不开高精度的检焦系统,单独设计的检焦系统不仅会增加全系统结构的复杂度,还会增加装调的难度。因此提出一种基于深度学习的检焦方法,通过调节光路使曝光焦面和相机成像焦面重合,仅根据当前所成的图像即可实现焦平面的快速自动检测。该算法由粗检焦和精检焦两步组成,粗检焦利用深度学习模型对相机记录的图像进行分类,仅需90 ms就可判断当前基片的离焦区间;精检焦利用清晰度评价函数计算图像清晰度值,结合搜索算法即可在粗检焦的基础上准确找到焦平面。用5倍聚焦物镜进行实验,在(-40μm,40μm)的离焦区间内,检焦精度可达2μm,总用时不超过300 ms。仿真分析和实验验证结果表明,该方法具有结构复杂度低、检焦速度快、检焦精度高等优点,能够很好地应用于数字光刻领域。Digital lithography based on digital micromirror array devices is one of the methods for the production of micro and nano structures,with the advantages of low cost and high flexibility,and has great advantages in micro and nano processing.As the demand for higher resolution of micro and nano structures increases,the wavelengths of lithography systems are getting shorter and the numerical apertures are getting larger,which leads to shorter and shorter exposure depths of focus.To ensure the quality of lithography patterns,the substrate must be within the depth of focus,so fast and high precision inspection of the focal plane becomes the key to the production of high resolution micro and nano structures.Most of the traditional methods require a separate design of the focus detection system,which will not only increase the complexity of the whole system structure but also increase the difficulty of mounting.With the growing development of image processing technology,focusing methods do not require complex optical path adjustment and can achieve focal plane detection based on out-of-focus images only,and the methods have been applied to many fields.Inspired by this,this paper proposes a deep learning based focus detection method,by adjusting the optical path of digital lithography so that the exposure focal plane and the camera imaging focal plane coincide,at this time the image captured by the CCD is the exposure pattern on the exposure focal plane,the blurred degree of the image directly reflects the out-of-focus degree of the exposure pattern,so the focal plane can be quickly and automatically detected using the algorithm only based on the currently formed image.The focus detection algorithm proposed in this study consists of two steps,firstly a coarse focus detection of the substrate at a large out-of-focus distance to reduce the out-of-focus range of the substrate,and then a further improvement of the focus detection accuracy at a small out-of-focus distance.According to the characteristics of these two focusing

关 键 词：数字光刻 自动检焦 深度学习 图像处理 

分 类 号：O436[机械工程—光学工程]