Opt Express. 2023 Feb 13;31(4):6552-6565. doi: 10.1364/OE.481389.
We propose a polarized, angle-resolved spectral (PARS) reflectometry for simultaneous thickness and refractive-index measurement of ultra-thin films in real time. This technology acquires a two-dimensional, angle-resolved spectrum through a dual-angle analyzer in a single shot by radially filtering the back-focal-plane image of a high-NA objective for dispersion analysis. Thus, film parameters, including thickness and refractive indices, are precisely fitted from the hyper-spectrum in angular and wavelength domains. Through a high-accuracy spectral calibration, a primary PARS system was built. Its accuracy was carefully verified by testing a set of SiO thin films of thicknesses within two µm grown on monocrystalline-Si substrates against a commercial spectroscopic ellipsometer. Results show that the single-shot PARS reflectometry results in a root-mean-square absolute accuracy error of ∼1 nm in film thickness measurement without knowing its refractive indices.
我们提出了一种用于实时同时测量超薄膜厚度和折射率的偏振角度分辨光谱（PARS）反射率测量法。该技术通过在高数值孔径物镜的后焦平面图像上进行径向滤波，以色散分析为目的，在单次拍摄中通过双角度分析器获取二维角度分辨光谱。因此，可以从角域和波长域的超光谱中精确拟合膜参数，包括厚度和折射率。通过高精度光谱校准，构建了一个初步的 PARS 系统。通过用商业光谱椭偏仪对一组厚度在 2μm 以内的生长在单晶-Si 衬底上的 SiO 薄膜进行测试，仔细验证了该系统的准确性。结果表明，在不知道薄膜折射率的情况下，单次拍摄的 PARS 反射率测量法在薄膜厚度测量方面的均方根绝对精度误差约为 1nm。
