在光谱椭偏测量中，玻璃基底的背反射会给测量结果造成较大影响。针对平板显示器件玻璃基底表面氮化硅镀膜进行了椭偏测量和模型计算。采用相干背反射模型“空气基底空气”计算并拟合得到与厂商数据符合较好的玻璃基底折射率。对氮化硅薄膜采用Tauc Lorentz色散模型进行了分析拟合，讨论了薄膜与基底界面层、表面粗糙度对光学常数及模型拟合的影响，表明在薄膜与基底间晶格失配的情况下，界面层的引入对改善拟合度是必要的。给出了薄膜体系的光学常数、薄膜结构的分析结果。

In spectroscopic ellipsometric measurement, the backside reflection of the glass substrate has great influence on the tested results. Ellipsometric measurement and model calculation are carried out for the silicon nitride film deposited on glass substrate of flat panel displays. The coherent model of the baskside reflection, i.e. "air-substrate-air" is used to calculate and obtain the refractive index of the glass substrate which agrees well with the data provided by manufacturer. Tauc Lorentz model is used in data analysis for the silicon nitride film to discuss the effect of the interface layer between the film and substrate, the surface roughness on the optical constants and model fitting. The results suggest that the inclusion of the interface is necessary for improving the degree of fitting in the case of lattice mismatch between the film and substrate. The optical constants and film structure of the film system are presented.