基于叠栅条纹的光刻对准理论分析及标定方法

Theoretical Analysis of Photolithography Alignment and Calibration Method Based on Moiré Fringes

在线光栅用于纳米光刻对准理论的基础上,为实现光栅方向的标定和掩模硅片对准,提出一种利用相位斜率消除角位移的新方法,并给出线光栅标记及其对准原理。在对准前,掩模对准标记和硅片对准标记存在角位移,重点讨论了此种情况下叠栅条纹的特性以及与光栅物理参数的关系,并给出了相应的计算公式。基于傅里叶频域分析法,对叠栅条纹频率成分与条纹的关系做了简要分析。利用提取叠栅条纹行列方向的一维相位,通过数据拟合,得出了相位斜率与角位移的内在关系,实现了条纹方向的标定。模拟实验结果表明,该方法简单可靠,可分辨的最小角位移低于0.02°。

To realize the calibration of grating direction and alignment between mask and wafer,on the basis of theory of line grating used for photolithography alignment,a novel method for eliminating angular displacement using phase slope is proposed.Line grating masks and their alignment principle are also given.Before alignment,there exists angular displacement between mask alignment marks and wafer alignment masks.The nature of Moiré fringes and their relation with physical parameters of grating are mainly discussed,and the corresponding calculation formulas are obtained.According to Fourier method of frequency domain,relation between Moiré fringe frequency components and stripes is briefly analyzed.Using extracted one dimensional phase of Moiré fringes in ranks,inner relation between phase slope and angular displacement is obtained by data fitting,and calibration of stripe direction is realized.Simulation experimental results show that this method is simple and reliable,minimum angular displacement with less than 0.02° can be identified.