摘要
半导体芯片等微纳器件制造过程中,对其形貌进行表征有助于制造工艺评估和缺陷检测。为了获得待测样品完整的信息,通常需要使用明场显微镜、暗场显微镜等进行多种成像模式的联合表征。但目前实现多模式成像常须更改实验装置或使用不同的成像系统,导致获取的多模式图像的视场不同,不利于将多模式成像结果综合起来对待测样品进行全面分析。针对以上问题,提出基于单像素成像原理的多模式显微成像技术。该技术将宽场照明显微镜中的光源替换成结构照明光源,然后将相机每个像素点作为单像素探测器,并利用单像素重建算法得到艾里斑图像。艾里斑图像中不同位置的值代表不同物点发出的不同级次的衍射信号。通过从艾里斑图像中提取不同位置的值,按照相机像素坐标排列,可以重建不同模式的图像。与传统的多模式显微成像方法相比,所提基于单像素成像原理的多模式显微成像技术采用同一套装置和相同的实验数据,重建的多模式图像的视场相同。所提方法为显微成像技术的发展提供了一种全新的思路,有望在微纳器件的离线形貌表征中得到应用。
Objective In the manufacturing of micro-nano devices such as semiconductor chips,their morphology characterization is helpful for manufacturing process evaluation and defect detection.To obtain complete information on the sample to be tested,one has to use bright field microscopes and dark field microscopes for joint characterization of multiple imaging modes.However,the existing methods to achieve multi-mode imaging need to change the experimental device or adopt a different imaging system,which leads to different fields of view of the acquired multi-mode images and is not conducive to comprehensively analyzing the samples to be tested by synthesizing the multi-mode imaging results.Therefore,it is necessary to develop multi-mode microscopic imaging technology to deal with the above problems.For example,microscopes based on LED array light source and multi-mode microscopic imaging technology using spatial light modulators are utilized to perform different filtering in the spectral plane of traditional microscopes.Methods Our paper proposes a multi-mode microscopic imaging technology based on the single-pixel imaging principle.It employs wide-field structured light to encode the spatial information of the sample and then leverages each pixel of the camera as a single-pixel detector to reconstruct an Ariy image.Different points on the Airy disk image correspond to different orders of signals diffracted by different object points.Therefore,by designing different digital pinholes to extract the values at different positions on the Airy disk image and arranging them according to the camera pixel coordinates,multimode images can be reconstructed,such as bright field images,bias images,and dark field images.Results and Discussions To design the digital pinhole to extract the signals of different diffraction orders of the sample,we should calibrate the conjugate relationship between the camera and the pixels of the spatial light modulator.We adopt an affine matrix to represent the correspondence between the camera and the spatial light modulator,and the calibrated reprojection error is shown in Fig.7.After the affine matrix is calibrated,digital pinholes can be generated according to the calibrated affine matrix.The proposed method is employed to perform multi-modal imaging on a circuit chip and obtain the multi-modal results shown in Fig.10.However,due to the directionality of digital pinholes,the reconstructed multimodal results are also anisotropic.To obtain isotropic multi-mode results,we design digital pinholes with the same radius and different directions as shown in Fig.12 to obtain multiple images and then synthesize these images to obtain isotropic results.The isotropic multi-mode results are shown in Fig.13.We have also verified through the resolution board experiment(Fig.14)that the contrast of the bright field images reconstructed by extracting the bias signals is higher than that of the bright field images constructed by extracting the zero-frequency signals.The proposed method adopts a Fourier single-pixel imaging algorithm that includes a differential operation to enable the suppression of out-of-focus background noise.However,due to the utilization of single-pixel imaging,the measurement number of the proposed method is more than that of the traditional multi-mode microscopic imaging method.Through taking the experimental results in our paper as an example and employing Intel(R)Core(TM)i7-10700 CPU@2.90 GHz,32.0 GB memory,it takes about 4 min to reconstruct four multi-mode images with a pixel count of 850×850,and the calculation time depends on the image number of pixels.Therefore,the proposed method is not suitable for dynamic imaging scenes.Conclusions Our paper proposes a multi-mode microscopic imaging technique based on the single-pixel imaging principle.It adopts each pixel of the camera as a single-pixel detector to reconstruct an Airy disk image,and the values at different positions in the Airy disk image represent different orders of signals diffracted by different object points.The experimental results show that this technology does not need to change the experimental device or replace different microscopes.By designing different digital pinholes,the light intensity values at different positions can be extracted from the single-pixel reconstructed Airy disk images.These light intensity values correspond to different orders of diffraction signals from different object points.By arranging these extracted signals according to the camera pixel coordinates,images of different modes can be reconstructed,such as bright field imaging,bias imaging,and dark field imaging.The fields of view of these multi-mode images are the same,which is conducive to the comprehensive analysis and acquisition of the complete shape characteristics of the samples.As a new computational imaging method,the proposed method is expected to be applied to the offline characterization of micro-nano devices.
作者
李东哲
周维帅
黄素仪
姚曼虹
李仕萍
彭军政
钟金钢
Li Dongzhe;Zhou Weishuai;Huang Suyi;Yao Manhong;Li Shiping;Peng Junzheng;Zhong Jingang(Department of Optoelectronic Engineering,College of Science&Engineering,Jinan University,Guangzhou 510632,Guangdong,China;School of Optoelectronic Engineering,Guangdong Polytechnic Normal University,Guangzhou 510665,Guangdong,China;Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications,Jinan University,Guangzhou 510632,Guangdong,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2023年第21期90-102,共13页
Acta Optica Sinica
基金
广东省基础与应用基础研究基金自然科学基金(2019A1515011151,2020A1515110392,2022A1515011560,2023A1515011277)。
关键词
多模式显微成像
单像素成像
明场成像
偏置成像
暗场成像
multi-mode microscopic imaging
single-pixel imaging
bright field imaging
bias imaging
dark field imaging
