单幅圆条纹相位展开光刻对准研究

Alignment in Lithography with Single Circular Fringe Pattern Phase Unwrapping

针对光刻对准中产生的单幅封闭干涉条纹经相位解析后获得的包裹相位,提出在极坐标系对其进行相位展开进而获得对准偏移量的方法.该方法首先将对准过程中两圆光栅相对移动产生条纹的相位分布从直角坐标系转换到极坐标系;其次分析在极坐标系下对准偏移量与相位参量的关系;最后通过取不同径向半径获得初始相位振幅与相位延迟进而求取对准偏移量.数值模拟与实验验证该方法的可行性并与传统的最小二乘与路径跟踪相位展开方法进行了对比分析.结果表明该方法对包裹相位进行展开进而达到几十纳米量级的高准确度对准,具有很强的适应性.

The phase unwrapping method based on the polar coordinate to get the alignment offset was proposed for the wrapped phase generated after the single closed interference fringe phase extraction in alignment of nanolithography.The phase distribution of the fringe pattern occurs in the relative movement between two circular gratings was transformed from rectangular coordinates system to polar coordinates system firstly;then the relationship between the alignment offset and the phase parameter was analysis in polar coordinates system;the initial phase amplitude and phase delay in different radial radius were got to acquire the alignment offset finally.The feasibility of the method was verified by numerical simulation and experiment and the comparisons of the tradition least squares method and path tracking method are given.The results show that the wrapped phase can be unwrapped for the alignment with high precision in tens of nanometers through the method with good adaptability.