厚度误差对THz-TDS的测量不确定度分析

阐述了基于菲涅尔公式的透射式太赫兹时域光谱系统提取样品光学常数的方法和原理,分析了样品厚度误差对THz-TDS测量不确定度的影响,并建立了相应的不确定度模型。进行太赫兹时域光谱测量实验,提取硅片在太赫兹波段的折射率,并计算了误差对提取样品折射率的影响。结果表明,随着厚度误差的增大,系统测量偏差也随之增大。对于较厚样品,相同厚度误差对其测量结果影响较小。样品厚度为994μm时,在厚度存在1μm的测量误差情况下,系统测量折射率的偏差为0.001 2,接近模型的仿真值。实验结果验证了厚度误差对测量不确定度模型的有效性,了解了厚度误差对系统测量结果的影响情况,对测量过程及结果分析具有一定的指导意义。

Analysis of Measurement Uncertainty in THz-TDS Carried by Thickness Error

The method and theory of extracting the sample optical constants with terahertz time domain system(THz-TDS) based on Fresnel formulas were demonstrated, the effect on the uncertainty of THz-TDS due to the thickness error was analyzed, and the uncertainty model was established. The measurement experiment of THz-TDS was designed, the refractive index of silicon wafer in terahertz band was extracted and the effect of error on extracting refractive index of sample was computed. Experimental results indicate that the measurement deviation increases with the thickness error increasing. For thicker samples, it has less effect on the measurement result carried by the same thickness error. The deviation of the refractive index measured by the system under 1 μm thickness error is 0.001 2 when the thickness of the sample is 994 μm, which is close to the simulation value of the model. Experimental results verify the availability of thickness error uncertainty model in measurement process, show the influence of thickness error on the measurement result, and have certain guiding significance on measure process and result analysis.