摘 要

当薄膜厚度降到纳米量级时，表现出不同于体材料的光学特性、电磁特性和力学特性，在现代科技中有着广泛的应用。纳米薄膜的独特性能与薄膜厚度有着密切的关系。而金属的介电常数为复数，导致其在常用的可见至红外光谱区吸收严重，因此实现对纳米金属薄膜厚度的准确测量是一个难题。目前通用的纳米级薄膜测量方法主要有台阶仪法、电子显微镜法和光学测量法。光学测量方法因为具有精度高、速度快、非接触测量等优势而成为主要的检测手段。

白光干涉是近年来发展起来的一种高精度、可实现绝对测量的方法。为了探究白光干涉法测量纳米金属薄膜厚度的可行性，本论文基于白光干涉理论，推导出了薄膜反射率与薄膜厚度，干涉峰值点级数与其对应波长值的关系公式。用MATLAB仿真得到了金、银薄膜反射率与薄膜厚度的关系曲线；作为对比，计算了不同厚度对应的锗膜、金膜和银膜干涉峰值点与对应波长值的关系图，得到了不同膜厚下各薄膜产生干涉波峰的最大波长值。

设计了白光干涉测量薄膜厚度的系统，并根据设计的系统结构搭建实验平台，以半导体锗膜和贵金属银两种材料为对象进行测量实验，采集了厚度未知的锗膜和银膜的白光干涉实验数据。对比分析实验测量的结果与仿真结果，证明了实验系统可以准确测量对应于工作波长吸收相对较弱的锗纳米薄膜的厚度；虽然由于银膜在工作波长的强吸收未能实现厚度的测量，但是提出了在本系统的基础上，通过调整工作波长可能实现银纳米级薄膜厚度的测量方案。最后，总结和分析了实验误差的主要来源，包括贵金属吸收性质、解调方法的选取以及实验条件的限制等。

关键词：厚度；纳米薄膜；白光干涉

Abstract

When the film thickness is reduced to nanometer level, it shows different optical, electromagnetic and mechanical characteristics from bulk materials, and it is widely used in modern science and technology. The unique properties of non-films are closely related to the film thickness. However, the dielectric constant of metal is complex, which leads to its serious absorption in common visible to infrared spectral regions, so it is a difficult problem to realize accurate measurement of non-metal film thickness. At present, the commonly used methods for measuring nanoscale thin films mainly include step meter method, electron microscope method and optical measurement method. Optical measurement method has become the main detection means because of its advantages of high accuracy, high speed and non-contact measurement.

White light interference is a kind of high-precision and absolute measurement method developed in recent years. In order to explore the feasibility of white light interference method to measure the thickness of non-metal thin films, based on the white light interference theory, this paper deduces the formula of the relationship between the reflectivity of thin films and the thickness of thin films, the number of interference peak points and their corresponding wavelength values. The relationship curve between the reflectivity of gold and silver films and the film thickness was obtained by MATLAB simulation. As a comparison, the relationship between interference peak points of germanium film, gold film and silver film with different thicknesses and corresponding wavelength values is calculated, and the maximum wavelength value of interference peak generated by each film with different thicknesses is obtained.
A white light interference measurement system for thin film thickness is designed, and an experimental platform is built according to the designed system structure. taking semiconductor germanium film and noble metal silver as objects, the white light interference experimental data of germanium film and silver film with unknown thickness are collected. By comparing and analyzing the experimental measurement results with simulation results, it is proved that the experimental system can accurately measure the thickness of germanium non-films with relatively weak absorption at the working wavelength. Although the thickness measurement can't be realized due to the strong absorption of silver film at the working wavelength, it is proposed that the thickness measurement scheme of silver non-film can be realized by adjusting the working wavelength on the basis of this system. Finally, the main sources of experimental errors are summarized and analyzed, including the absorption properties of precious metals, the selection of demodulation methods and the limitation of experimental conditions.

Key Words：Thickness; Nanometer film; White light interference

目 录

第1章 绪论 1

1.1 研究背景 1

1.1.1 纳米级薄膜厚度测量的研究历史及现状 1

1.1.2 白光干涉法测量纳米级薄膜厚度的研究历史及现状 2

1.1.3 金属薄膜的应用 3

1.2 研究目的及意义 3

1.3 论文的研究内容与章节安排 3

第2章 白光干涉薄膜厚度测量法 5

2.1 白光干涉测量膜厚的原理 5

2.2 白光干涉解调原理 6

2.3 薄膜的选取原理 6

第3章 白光干涉法测量纳米薄膜厚度的仿真与实验 8

3.1 仿真 8

3.1.1 薄膜反射率与薄膜厚度的仿真 8

3.1.2 薄膜入射波长与峰值的仿真 10

3.2 膜厚检测实验系统 14

3.3 金属薄膜厚度测量的实验结果 15

3.3.1 锗膜厚度测量结果 15

3.3.2 银膜厚度测量结果 17

3.3.3 测量误差分析与讨论 18

3.4 实验系统改进 19

第4章 结论 20

4.1 本文结论 20

4.2 本文总结与展望 20

参考文献 21

致 谢 23

绪论

• 1. 研究背景
     1. 纳米级薄膜厚度测量的研究历史及现状

薄膜是指沉淀在基底表面的分子、原子或者离子在表面形成的一种特殊二维材料。随着构成薄膜的晶粒尺寸的减小，晶界密度增加，其表面不平度也将发生变化，所以当薄膜尺寸降低到纳米量级（几纳米到几百纳米）时，光学性质会发生改变。随着材料科学和镀膜技术的不断发展，对于厚度在纳米量级的薄膜的研究和应用逐年增加，纳米薄膜不仅仅应用于传统光学领域，在生产实践中也得到越来越广泛的应用。在纳米薄膜的各项参数中，薄膜的厚度是薄膜设计和制备过程中的重要参量，是决定薄膜性质的最基本参量之一，在薄膜光学、力学和磁性能方面也具有重要的影响。

随着科技的不断发展和研究的推进，对于薄膜厚度的测量方法不断改进，实现了从手动到自动，从有损到无损的进步。对于不同的待测薄膜材料，由于其具有不同的性质，其适用的测量方法也不相同。对于薄膜厚度的测量方法，可以大致分为光学方法和电学方法两类，非光学方法主要有涡流和探针法，光学方法主要有椭圆偏振法，干涉法，反射法，光谱法以及棱镜耦合法^[1]。由于光学方法具有高精度，速度快，无损测量等优势，光学方法成为主要的检测方法。