采用不同的光学模型对厚度为6nm,密度为2.2 g/cm3的理想SiO2薄膜理论曲线进行了拟合,得到了薄膜厚度的计算结果随所采取的薄膜密度变化的规律:选用更大的薄膜密度值进行拟合计算会得到更小的厚度结果,其趋势近似线性.参考GIXRR方法测量得到的薄膜物理结构的结果,给出了优化的拟合计算模型(薄膜密度为2.4 g/cm3、表面粗糙度为0.4nm、界面粗糙度为0.3 nm),对于热氧化法制备的厚度小于10 nm的SiO2超薄膜,使用此模型进行拟合计算,可以得到比常规模型更为准确的厚度结果.采用优化的模型拟合了期望厚度为2,4,6,8,10 nm的SiO2超薄膜的SE实验曲线,得到的厚度结果分别为2.61,4.07,6.02,7.41,9.43 nm,与传统模型计算结果相比,分别降低了13.8％,10.3％,8.1％,7.3％和6.6％.%Different optical models were adopted to fit the theoretical simulation curves of a SiO2 ultra-thin film with a density of 2. 2 g/cm3 and a thickness of 6 nm. The results indicate that the thickness obtained from fitting decrease approximately linearly with the increase of film density. An improved optical model (density of thin film: 2.4 g/cm3, roughness of surface: 0.4 nm, roughness of surface: 0.3 nm) was obtained according to the above analysis and the GIXRR results, which could give more accurate thickness value of the ultrathin film with the thickness less than 10 nm. It was employed in the calculation of the thickness of the thermal oxidized SiO2 thin film with nominal thicknesses of 2, 4, 6, 8 and 10 nm. The results were 2. 61, 4.07, 6.02, 7.41 and 9. 43 nm, decreased by 13.8%, 10.3%, 8.1%, 7.3% and 6.6%, respectively, compared with the results from the traditional model.
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