Mesoscopic-scale and small strain field beneath SiO₂/Si interface revealed by a multiple-wave X-ray diffraction phenomenon-depth of the strain field

Small strain field distributed over a mesoscopic-scale beneath SiO ₂/Si interface was investigated by using intensity of CTR scattering modulated by a Bragg reflection, which is a multiple-wave X-ray diffraction phenomenon. Assuming that the depth-profile of the total displacement of the strained layer is expressed by an exponential function, we calculated the intensities of the CTR scattering and the Bragg reflection on the basis of the threewave Darwin theory. The results showed that the modulation is sensitive to the total displacement of the atomic layers in the strained layer, while the curve of the Bragg reflection is sensitive to the depth of the strained layer. We compared the results of the numerical calculations with the experimental results of a Si(0 0 1) wafer covered with a thermal oxide layer, which was formed by wet oxidation process at 900 ° C, and found that the total displacement in the strained layer is 0.132Å and the depth of the strain field is a few hundreds of nanometers.