一种基于遗传算法的单弹光调制高速椭偏技术  

A High Speed Ellipsometry Technology for Single Photoelastic Modulation Based on Genetic Algorithm

作　　者：徐承雨 张瑞[1,2] 薛鹏[2] 郭浩杰 王赛飞 吕健宁 武振涛 王志斌[2] XU Chengyu;ZHANG Rui;XUE Peng;GUO Haojie;WANG Saifei;LÜJianning;WU Zhentao;WANG Zhibin(School of Information and Communication Engineering,North University of China,Taiyuan 030051,China;Technology Innovation Center of Shanxi Provincial for Intelligent Microwave Photoelectric,North University of China,Taiyuan 030051,China)

机构地区：[1]中北大学信息与通信工程学院,山西太原030051 [2]中北大学山西省智能微波光电技术创新中心,山西太原030051

出　　处：《测试技术学报》2025年第2期155-163,共9页Journal of Test and Measurement Technology

基　　金：国家自然科学基金资助项目(62105302)。

摘　　要：针对单弹光椭偏测量技术需锁相多个周期信号、无法快速获得样品光学椭偏参数和薄膜厚度等问题,提出一种基于弹光调制器(PEM)偏振调制和单调制周期遗传算法参数提取的高速单弹光调制椭偏测量方法,该方法的时间分辨率可达μs量级。为保证算法的精度与稳定性,利用系统输出单个调制周期干涉信号的极值对系统PEM的相位延迟幅值(δpeak)进行校准并且确定样品的光学椭偏参数范围。通过该校准方法可以确定待测参数范围,大幅缩短计算时间,提升计算精度。对空气以及61.4 nm和100 nm厚度的硅上镀二氧化硅样片进行测量,实验表明该系统PEM的静态相位延迟(δstatic)在测量范围内稳定波动,最大偏差为0.0073 rad,标准差为0.0033 rad,δpeak与FPGA输出信号的占空比线性拟合系数R2为0.9995;样品薄膜测量厚度与其真值的相对误差小于0.1%且偏差在1 nm以内,椭偏参量测量所需调制信号时间为8.3μs,较传统弹光锁相椭偏方法快1~2数量级。该方法实现的高速单弹光调制椭偏测量技术具有较高的精度和稳定性,为后续研究高速多弹光调制椭偏技术奠定基础。A high-speed single photoelastic modulation(PEM)ellipsometry measurement method based on polarization modulation of PEM and parameter extraction of single modulation period genetic algorithm is proposed to address the issues of phase locking multiple period signals and inability to quickly obtain sample optical ellipsometric parameters and thin film thickness in single PEM measurement technology.The time resolution of this method can reach up toμs level.To ensure the accuracy and stability of the algorithm,the phase delay amplitude(δpeak)of the PEM system is calibrated by the extremum of the interference signal within a modulation period of the system and the optical ellipsometry parameter range of the sample is determined.This calibration method can significantly shorten the calculation time and improve the calculation accuracy.By measuring the air and samples(made of silicon dioxide coated on silicon with thicknesses of 60 nm and 100 nm),the experiment shows that the static phase delay(δstatic)of the PEM system fluctuates stably within the measurement range.The maximum deviation ofδstatic is 0.0073 rad,and the standard deviation is 0.0033 rad.The linear fitting coefficient R2 of the duty cycle betweenδpeak and FPGA output signals is 0.9995.The experiments show that the relative error between the measured thickness of the sample film and its true value is less than 0.1%and the deviation is within 1 nm.The required modulation signal time for ellipsometric parameter measurement is 8.3μs,which is 1~2 orders of magnitude faster than traditional PEM phase-locked ellipsometry methods.The results show that the high-speed single PEM ellipsometry mea-surement technology achieved by this method has high accuracy and stability,and lays the foundation for subsequent research on high-speed multi-PEM ellipsometry technology.

关 键 词：高速椭偏测量 弹光调制 遗传算法 图像拟合仿真 

分 类 号：TP212[自动化与计算机技术—检测技术与自动化装置]