Nagaraj Rao Ratish Rao, Bienert Florian, Moeller Michael, Bashir Danish, Hamri Alina, Celle Frederic, Gamet Emilie, Ahmed Marwan Abdou, Jourlin Yves
Opt Express. 2023 Jan 2;31(1):371-380. doi: 10.1364/OE.478688.
Gratings produced by two-spherical-beam Laser Interference Lithography (LIL) will have a nonuniform period, and the associated period variation is larger with the increase of the substrate size. This work quantitatively investigates a noninvasive method for improving the period variation on 4-inch silicon wafers. By temporarily deforming the flexible silicon wafer using a customized concave vacuum chuck [J. Vac. Sci. Technol. B19(6), 2347 (2001)10.1116/1.1421558], we show that the fabricated gratings will have improved period uniformity, with the period variation reduced by 86% at the 1000 nm central grating period setting. This process is a simple and efficient way to achieve linear gratings without altering the LIL configuration with two spherical beams. We present experimental results on the impact of a concave vacuum chuck on the chirp reduction at different grating period settings. Then, we compare two different LIL configurations with different wavelength sources concerning their influence on the efficiency of period variation reduction. Finally, the flatness of the 4-inch silicon wafers due to the temporary bending process is verified using optical profilometry measurements.
通过双球面光束激光干涉光刻（LIL）制作的光栅会具有不均匀的周期，并且随着衬底尺寸的增加，相关的周期变化会更大。这项工作定量研究了一种用于改善4英寸硅片上周期变化的非侵入性方法。通过使用定制的凹面真空吸盘使柔性硅片暂时变形[《真空科学与技术杂志B》19(6)，2347(2001)10.1116/1.1421558]，我们表明所制作的光栅将具有改善的周期均匀性，在1000 nm中心光栅周期设置下，周期变化减少了86%。此过程是一种简单有效的方法，可在不改变双球面光束LIL配置的情况下实现线性光栅。我们展示了关于凹面真空吸盘在不同光栅周期设置下对啁啾减少影响的实验结果。然后，我们比较了具有不同波长源的两种不同LIL配置对减少周期变化效率的影响。最后，使用光学轮廓测量法验证了由于临时弯曲过程导致的4英寸硅片的平整度。
