摘要
针对车间环境下晶圆抛光盘面形测量问题,提出使用基于扩束动态干涉仪的掠入射拼接干涉测量方法。该方法结合非球面扩束系统和子孔径拼接方法,弥补了动态干涉仪测量口径的不足;利用掠入射干涉测量解决了粗糙被测面光束散射问题,同时拓展了动态干涉仪的面形误差检测量程。研究了系统出射波前离焦变化问题,基于像散光圈自校准的子孔径拼接算法,有效消除了子孔径拼接过程中系统离焦的干扰,为高精度子孔径拼接测量提供算法保障。测量了直径为576 mm晶圆抛光盘样品表面,并与三坐标机测量结果进行对比。所提方法的截线高度测量结果的平均误差为0.1375μm,平面度误差为0.17μm。实验结果表明,所提方法具备晶圆抛光盘面形检测能力,拓展了动态干涉仪的应用范围。
Objective The wafer polishing pad is a critical component in achieving global planarization of the wafer surface during the integrated circuit manufacturing process.Its surface shape has a significant effect on wafer yield.To optimize the shape of the wafer polishing pad,strict quality control measures are necessary.Precision measurement technology plays a vital role in ensuring quality.Currently,the integrated circuit industry is moving towards larger wafer sizes and smaller feature dimensions,presenting new challenges for measuring the shape of wafer polishing pads.Interferometry is one of the most effective and intuitive methods for surface measurement due to its non-contact nature,high accuracy,and rapid operation.However,traditional large-aperture Fizeau interferometers face significant manufacturing difficulties and high costs.Moreover,they often struggle to accurately measure the surface shapes of large-diameter wafer polishing pads due to limitations such as restricted dynamic range,light scattering,and diminished stripe contrast.Grazing-incidence interferometry provides an effective solution to these limitations,addressing issues related to aperture size,dynamic range,and contrast.Nevertheless,when measuring large-diameter wafer polishing pads with long interferometric cavity lengths,new challenges such as airflow disturbances and vibrations emerge.To address these issues,we propose to measure the surface shape of large-aperture wafer polishing pads using a grazing incidence splicing technique within a beam-expanding dynamic interferometer.Methods The challenges related to aperture size,dynamic range,and contrast in the interferometric measurement of large-aperture wafer polishing pad surfaces are effectively addressed through grazing incidence interferometry and subaperture stitching techniques.A high-precision and high-stability beam expansion system effectively compensates for the limitations of the dynamic interferometer regarding measurement aperture.At the same time,the inherent anti-interference capabilities of the dynamic interferometer can address the issue of environmental disturbances affecting the grazing incidence light path of large-aperture optical components.Based on a self-calibrating sub-aperture stitching algorithm,the influence of system defocus on grazing incidence measurements is decomposed into unequal astigmatic circles in the x and y directions,which are then deducted.This approach enables the measurement of the surface shape of large-diameter rough optical elements by correcting the defocus-induced errors of the beam-expanding dynamic interferometer.Results and Discussions We develop a 150 mm beam-expanding dynamic interferometer to conduct wavefront calibration experiments.We perform outgoing wavefront stability monitoring experiments with different clamping configurations for the beam expansion collimators.The results indicate that the distributed fastening screw clamping scheme has better stability than the hard-contact clamping scheme using polytetrafluoroethylene(PTFE)pads.It maintains a wavefront peak valley(PV)value stable at approximately 0.1λover a period of 9 h,with a maximum deviation not exceeding 0.108λ.Using the 150 mm beam-expanding dynamic interferometer,we collect sub-aperture data from aФ576 mm polishing pad sample produced by KYOCERA Corporation in Japan.The data are stitched together using both a standard stitching algorithm and a self-calibrating astigmatic circle algorithm.The results reveal that the standard stitching algorithm is significantly affected by defocus-induced system errors,resulting in jump errors at the sub-aperture junctions.In contrast,the self-calibrating sub-aperture stitching algorithm effectively mitigates the influence of system errors,yielding a smooth transition.Ultimately,the stitched wavefront yields a PV value of 4.784λand a root-mean-square value of 1.151λ.A comparison is made between the central cross-sections of the composite surface shape at angles of 0°,45°,90°,and 135°and the measurements from a coordinate measuring machine provided in the sample’s factory report.The average measurement error for the cross-section heights is 0.1375μm,while the flatness error is 0.17μm,both within acceptable limits.Conclusions We develop a grazing incidence splicing surface error measurement method based on beam expanding dynamic interferometer,which can solve the problem of surface error detection of large diameter wafer polishing pad in workshop environment.We investigate the issue of defocus variation in the system’s outgoing wavefront and employ a selfcalibrating astigmatic circle sub-aperture stitching algorithm to decompose the influence of system defocus on grazing incidence measurements into unequal astigmatic circles in the x and y directions,which are then corrected.Simulation results demonstrate that this algorithm can effectively eliminate the interference caused by system defocus during subaperture stitching,providing a robust algorithmic foundation for high-precision sub-aperture measurements.Experimental comparisons are conducted to assess the degradation of the system’s outgoing wavefront under different clamping configurations over the same period.The results indicate that the distributed fastening screw clamping scheme significantly enhances system stability.A sub-aperture stitching detection device based on a grazing incidence beam-expanding dynamic interferometer is established to measure aФ576 mm wafer polishing pad sample.Comparing the measurement results with those from the factory’s coordinate measuring machine reveals that the average measurement error for cross-section heights is 0.1375μm,while the flatness error is 0.17μm.Experimental results demonstrate that this method can inspect the surface error of wafer polishing pads,thereby expanding the application scope of dynamic interferometers.
作者
芮九多
巫智勋
邓嘉信
张嘉博
韩志刚
王青
朱日宏
Rui Jiuduo;Wu Zhixun;Deng Jiaxin;Zhang Jiabo;Han Zhigang;Wang Qing;Zhu Rihong(School of Electronic and Optical Engineering,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China;MIIT Key Laboratory of Advanced Solid Laser,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China)
出处
《光学学报》
北大核心
2025年第2期183-194,共12页
Acta Optica Sinica
基金
国家自然科学基金(61875087)。
关键词
晶圆抛光盘
动态干涉
掠入射
子孔径拼接
面形测量
wafer polishing pad
dynamic interference
grazing incidence
sub-aperture splicing
surface measurement
