| 摘要 |
PURPOSE:To evaluate a sample having unknown retractive index or density by extracting the oscillatory component from a measured X-ray reflectance, performing Fourier analysis while altering the refractive index, and displaying the Fourier transform intensity three-dimensionaily for the retractive index and frequency, thereby determining the optimal retractive index of a thin film causing a peak value. CONSTITUTION:An X-ray reflectance pattern measured for a sample of thin films 1, 2 formed on a substrate 3 is subjected to Fourier transform. Since the reflectance of each layer 1, 2 is unknown, Fourier transform is performed for the refractive index delta ranging over 10<-6>-10<-5>. Three peaks can be predicted from a two layer film but since four peaks A-D appeared, a decision is made that the peak B appearing at a frequency position two times as high as that of the peak A is an overtone. The Fourier transformed intensities of the retractive index and frequency are then displayed by three-dimensional level lines and a combination of refractive index and frequency corresponding to a maximal value is determined systematically. The film thickness is determined uniquely from the combination. Consequently, the film thickness and refractive index can be determined simultaneously for each layer. |
