发挥蝙蝠翼高频脉冲特性的微结构线宽超分辨测量方法  

Harnessing Batwing High-Frequency Pulse Traits for Super-Resolution Measurement of Microstructure Linewidth

作　　者：徐志毅 范筱昕 张佳乐 周圣航 郭珍艳 朱丹[1] 高志山[1] 袁群[1] Xu Zhiyi;Fan Xiaoxin;Zhang Jiale;Zhou Shenghang;Guo Zhenyan;Zhu Dan;Gao Zhishan;Yuan Qun(School of Electronic and Optical Engineering,Nanjing University of Science&Technology,Nanjing 210094,Jiangsu,China)

机构地区：[1]南京理工大学电子工程与光电技术学院,江苏南京210094

出　　处：《光学学报》2024年第13期137-144,共8页Acta Optica Sinica

基　　金：国家自然科学基金(62175107,62205148,62327814);国家重点研发计划(2022YFF0706302,2023YFF0720601);江苏省高校青蓝工程。

摘　　要：白光显微干涉是阶跃型微结构三维形貌无损测量的经典方法,但其低通滤波特性使阶跃边缘本应突变的三维形貌被平滑,导致边缘定位困难,影响线宽参数的计算提取。当微结构深度在光源相干长度内时,蝙蝠翼效应使阶跃边缘处的复原形貌产生尖锐脉冲。蝙蝠翼脉冲是三维形貌中的伪信号,但其高频特性更利于阶跃边缘的识别。微结构线宽为两阶跃边缘各自对应蝙蝠翼脉冲高度峰值位置的间距。然而,三维形貌空间采样频率受成像艾里斑和探测器像素大小限制,在线宽测量方向上通常仅有数个像素点受蝙蝠翼效应影响,通过蝙蝠翼脉冲高度峰值定位,线宽测量精度仅有像素级别。本文建立了针对蝙蝠翼效应及其离散采样特性的白光干涉信号数值仿真模型,发掘了线宽正交方向上样品阶跃边缘形貌的空域缓变特性,等效提高了蝙蝠翼脉冲在该方向的采样频率。据此提出了一种基于蝙蝠翼高度峰值位置高精度定位的微结构线宽超分辨白光干涉测量方法,并依据实测条件分析了样品位姿对测量精度的影响。以RSN标定板为样品,采用成像艾里斑半径约为0.590μm的测量系统,利用本文方法实测标定线宽2~6μm的光栅区域线宽结果与标定值偏差小于0.021μm,实验结果证明,该方法可以实现远高于系统横向分辨率的线宽超分辨测量。Objective White light microscopic interferometry is a traditional method for non-destructively measuring the threedimensional(3D) topography of step microstructures. However, its tendency for low-pass filtering smoothens the 3D topography along sharp step edges, making precise edge detection challenging and affecting the calculation and extraction of linewidth parameters. Moreover, when the depth of the microstructure is smaller than the coherence length of the light source, the batwing effect may generate sharp pulses in the recovered 3D topography at these step edges. Despite these pulses being spurious signals, their high-frequency traits are beneficial for identifying step edges. The microstructure linewidth is determined by the distance between the peak positions of the batwing pulse heights corresponding to the two step edges. The spatial sampling frequency of the 3D topography is constrained by the size of the Airy spot and the detector pixel. Typically, only a few pixels in the linewidth measurement direction are influenced by the batwing effect. It is crucial to note that the accuracy of linewidth measurement is confined to the pixel level, and is determined by the peak location of the batwing pulse heights. In this study, we propose a super-resolution measurement method for microstructure linewidth.It is based on precisely locating the peak positions of batwing heights in white light interferometry, surpassing the system's lateral resolution. We anticipate that our findings will enhance 3D topography measurement of step microstructures and advance our understanding of the batwing effect.Methods We introduce a numerical simulation model for white light interferometry signals, with a specific focus on the batwing effect and its discrete sampling characteristics. The model unveils the slow-varying attributes of the spatial domain orthogonal to the linewidth measurement direction, offering theoretical backing for improving the sampling frequency of batwing pulses in that direction. By harnessing the spuriou

关 键 词：线宽测量 超分辨 白光干涉 蝙蝠翼效应 信号采样 

分 类 号：TH741[机械工程—光学工程]