Measurement Science and Technology ( IF 2.4 ) Pub Date : 2021-05-18 , DOI: 10.1088/1361-6501/abfbac Xiujie Dou 1, 2 , Silvania F Pereira 1 , Changjun Min 2 , Yuquan Zhang 2 , Peiwen Meng 1 , H Paul Urbach 1 , Xiaocong Yuan 2
The sidewall angle (SWA) of a nanostructure exerts influence on the performance of the nanostructure and plays an important role in processing nano-structural chips. It is still a great challenge to determine steep SWAs from far field measurements especially when the SWAs are close to 90. Here, we propose a far-field detection system to determine steep SWA of a cliff-shape step structure on a silicon substrate by combining a split detector with a scanning method. The far-field radiation field is asymmetric due to the scattering of the step structure, and further numerical analysis demonstrates the reliability of this far-field measurement method. In the simulations, two key variables, i.e. the polarization state and the focus position of the incident laser beam, are considered to explore their impacts. By scanning over the structure laterally and longitudinally with both TE and TM polarizations, polarization effects on the far-field occur. These effects show higher sensitivity to steep SWA variation for TM polarization as compared to TE. Furthermore, with a comprehensive longitudinal scanning analysis for the TM polarization case, a feasible focus interval can be optimized to retrieve the steep SWA. As the proposed method is fast, highly sensitive and easy to implement, it provides a powerful approach to investigate the scattering behavior of nanostructures.
中文翻译:
使用偏振敏感的非对称散射确定陡峭的侧壁角
纳米结构的侧壁角(SWA)对纳米结构的性能产生影响,在加工纳米结构芯片中起着重要作用。从远场测量中确定陡峭的 SWA 仍然是一个巨大的挑战,尤其是当 SWA 接近 90 时。 在这里,我们提出了一种远场检测系统,通过结合采用扫描方法的分裂检测器。由于阶梯结构的散射,远场辐射场是不对称的,进一步的数值分析证明了这种远场测量方法的可靠性。在模拟中,考虑了两个关键变量,即入射激光束的偏振态和焦点位置,以探索它们的影响。通过使用 TE 和 TM 极化横向和纵向扫描结构,远场的极化效应发生。与 TE 相比,这些效应对 TM 极化的陡峭 SWA 变化表现出更高的敏感性。此外,通过对 TM 偏振情况的全面纵向扫描分析,可以优化可行的聚焦间隔以检索陡峭的 SWA。由于所提出的方法速度快、灵敏度高且易于实施,它为研究纳米结构的散射行为提供了一种强大的方法。可以优化可行的聚焦间隔以检索陡峭的 SWA。由于所提出的方法速度快、灵敏度高且易于实施,它为研究纳米结构的散射行为提供了一种强大的方法。可以优化可行的聚焦间隔以检索陡峭的 SWA。由于所提出的方法速度快、灵敏度高且易于实施,它为研究纳米结构的散射行为提供了一种强大的方法。