Shen Biyao, Zeng Lijiang, Li Lifeng
Appl Opt. 2016 Oct 20;55(30):8472-8477. doi: 10.1364/AO.55.008472.
We present an in situ duty cycle control method that relies on monitoring the TM/TE diffraction efficiency ratio of the -1st transmitted order during photoresist development. Owing to the anisotropic structure of a binary grating, at an appropriately chosen angle of incidence, diffraction efficiencies in TE and TM polarizations vary with groove depth proportionately, while they vary with duty cycle differently. Thus, measuring the TM/TE diffraction efficiency ratio can help estimate the duty cycle during development while eliminating the effect of photoresist thickness uncertainty. We experimentally verified the feasibility of this idea by fabricating photoresist gratings with different photoresist thicknesses. The experimental results were in good agreement with theoretical predictions.
我们提出了一种原位占空比控制方法，该方法依赖于在光刻胶显影过程中监测第 -1 级透射光的 TM/TE 衍射效率比。由于二元光栅的各向异性结构，在适当选择的入射角下，TE 和 TM 偏振中的衍射效率随槽深成比例变化，而它们随占空比的变化则不同。因此，测量 TM/TE 衍射效率比有助于在显影过程中估计占空比，同时消除光刻胶厚度不确定性的影响。我们通过制造具有不同光刻胶厚度的光刻胶光栅，实验验证了这一想法的可行性。实验结果与理论预测吻合良好。
