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采用声光调制器设计了一种透射式外差干涉椭偏测量系统。实验测量了单层透明氧化铟锡(ITO)膜,膜厚和折射率测量误差分别达8nm和7%。采用琼斯矢量法分析了金属反射镜引起的光束椭偏化对测量结果的影响。从光学系统中移出被测样品得到的标定数据,可以消除金属反射镜本身退偏效应的影响,但无法消除退偏效应和方位角误差共同作用所引入的椭偏参数测量误差。计算结果表明,退偏效应和方位角误差共同作用引入的膜厚测量误差可达4 nm左右,该误差与薄膜参数无关,与方位角误差近似成线性关系。
A transmissive heterodyne interference ellipsometry system is designed using acousto-optic modulator. A single layer of transparent ITO (Indium Tin Oxide) film was measured. The measurement error of film thickness and refractive index was 8nm and 7% respectively. Jones vector analysis of the metal mirror caused by the beam ellipsometry on the measurement results. The removal of the calibration data from the optical system can eliminate the effect of the depolarization effect of the metal mirror itself, but it can not eliminate the ellipsometric measurement error introduced by the combination of the depolarization effect and the azimuth error. The calculated results show that the error of film thickness measurement introduced by the combined effect of de-depolarization and azimuth error can reach about 4 nm. The error is independent of the film parameters and approximately linear with the azimuth error.