Hsieh Hung-Chih, Cheng Jui-Ming, Yeh Yun-Chi
Appl Opt. 2022 Feb 20;61(6):1389-1397. doi: 10.1364/AO.449500.
A robust and wafer-less wavelength selection methodology was proposed. An overlay calculation model considering the asymmetric bottom grating structure showed that additional intensities diffracted from the asymmetric structure caused the overlay error. An asymmetry factor was introduced to describe the intensity ratio of the original overlay mark and a mark with bottom grating only. Based on the simulation results, the optimized wavelength was selected by analyzing the wavelength at which there is the minimum variation of the asymmetry factor. Four cases were tested by the simulation, and the maximum overlay error of the optimized wavelength selected by this method was 0.21 nm.
提出了一种稳健的无晶圆波长选择方法。考虑非对称底部光栅结构的重叠计算模型表明，从非对称结构衍射出的额外强度会导致重叠误差。引入了一个不对称因子来描述原始重叠标记和仅具有底部光栅的标记的强度比。基于模拟结果，通过分析不对称因子变化最小的波长来选择优化波长。通过模拟测试了四种情况，该方法选择的优化波长的最大重叠误差为0.21nm。
