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Measurement of layer thicknesses with an improved optimization method for depolarizing Mueller matrices
Measurement Science and Technology ( IF 2.7 ) Pub Date : 2020-09-10 , DOI: 10.1088/1361-6501/ab95da
Tobias Grunewald 1 , Matthias Wurm 1 , Sven Teichert 1 , Bernd Bodermann 1 , Johanna Reck 2 , Uwe Richter 2
Affiliation  

For the analysis of measured data in spectroscopic Mueller ellipsometry (SME) there exist some commonly used optimization techniques to calculate for example layer thicknesses of samples under test. Concentrating on metrological aspects of SME we identified a non-optimal treatment of depolarization in all these techniques. Therefore, we recently developed an improved optimization method to take adequately into account depolarization in Mueller matrix ellipsometry (MME). In a further step we also included statistical measurement noise and derived a likelihood function, which enabled us to apply both the maximum likelihood method, Bayesian statistics and the Bayesian information criterion for the data evaluation. In this paper we concentrate on the application of that new method for calculating SiO2-layer thicknesses on Silicon. For that purpose with a state-of-the-art SENTECH SENresearch 4.0 MME we measured different SiO2-layer thickness standard samples with nominal thicknesses between 6 nm and 1000 nm, which have been calibrated by X-ray reflectometry (XRR) at PTB. The MME results are compared to the calibration data. For all samples an SiO2-SiO-Si model turned out to be optimal. The measured oxid layer thicknesses match excellently with the calibration values within the declared uncertainties. All results are presented here. It is a first comparison with traceable reference measurements demonstrating the validity of our novel MME analysis method.

中文翻译:

使用改进的优化方法测量层厚度,用于去极化 Mueller 矩阵

对于光谱穆勒椭偏仪 (SME) 中测量数据的分析,存在一些常用的优化技术来计算例如被测样品的层厚度。专注于 SME 的计量方面,我们确定了所有这些技术中去极化的非最佳处理。因此,我们最近开发了一种改进的优化方法,以充分考虑穆勒矩阵椭偏仪 (MME) 中的去极化。在进一步的步骤中,我们还包括统计测量噪声并推导出似然函数,这使我们能够同时应用最大似然法、贝叶斯统计和贝叶斯信息标准进行数据评估。在本文中,我们专注于计算硅上 SiO2 层厚度的新方法的应用。为此,我们使用最先进的 SENTECH SENresearch 4.0 MME 测量了标称厚度在 6 nm 到 1000 nm 之间的不同 SiO2 层厚度标准样品,这些样品已通过 PTB 的 X 射线反射仪 (XRR) 校准。MME 结果与校准数据进行比较。对于所有样品,SiO2-SiO-Si 模型被证明是最佳的。测得的氧化层厚度与声明的不确定度内的校准值非常匹配。所有结果都显示在此处。这是与可追溯参考测量值的首次比较,证明了我们新型 MME 分析方法的有效性。MME 结果与校准数据进行比较。对于所有样品,SiO2-SiO-Si 模型被证明是最佳的。测得的氧化层厚度与声明的不确定度内的校准值非常匹配。所有结果都显示在此处。这是与可追溯参考测量值的首次比较,证明了我们新型 MME 分析方法的有效性。MME 结果与校准数据进行比较。对于所有样品,SiO2-SiO-Si 模型被证明是最佳的。测得的氧化层厚度与声明的不确定度内的校准值非常匹配。所有结果都显示在此处。这是与可追溯参考测量值的首次比较,证明了我们新型 MME 分析方法的有效性。
更新日期:2020-09-10
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