基于柱面透镜Otto结构SPR效应的金属薄膜厚度测量方法

Thickness Measurement Method of Metallic Thin Film Based on SPR Effect Generated by Cylindrical Lens with Otto Configuration

基于柱面透镜修正Otto结构产生的表面等离子体共振(SPR)效应,提出一种测量金属薄膜厚度的方法。该方法无需用s偏振光提取背景光强,可直接利用在p偏振光入射条件下得到的单幅SPR吸收图像拟合背景光强,进而得到竖直方向上的归一化反射率曲线。从而建立光学薄膜模型并拟合了反射率曲线,反演出待测金属薄膜的厚度参数。实验对一个纳米级厚度的Au膜样品进行测量,测量结果表明,Au膜的平均厚度与商用光谱椭偏仪的测量结果之差为0.1 nm,验证了该方法的有效性。

Based on the surface plasmon resonance(SPR) effect caused by a modified Otto structure of cylindrical lens, a method for measuring the thickness of metallic thin films is proposed. For this proposed method, the background intensity can be fitted only with the single SPR absorption image obtained under the p-polarized light incidence, no need using the s-polarized light. Hence, the normalized reflectivity curve in the vertical direction is obtained. The reflectivity curve is fitted by establishing a model of the optical thin film and the thickness parameters of the metallic thin film are derived. In the experiment, a sample of Au film with a thickness in the nanometer range is measured. The measurement results show that the difference between the measured average thickness of Au film and the result obtained by commercial spectroscopic ellipsometer is only 0.1 nm, which verifies the effectiveness of this method.