Application of X-ray Diffraction Techniques to the Semiconductor Field

generally arranged at a distance of 0.1 nm to 0.5 nm from one another. When such a substance is irradiated with X-rays having a wavelength roughly equivalent to the interatomic or intermolecular distance, the Xray diffraction phenomenon will take place. X-ray diffraction is widely used in the semiconductor field because it is nondestructive and yields crystal structure information relatively easily in an atmospheric environment. Table 1 shows a summary of the application of X-ray diffraction techniques to the semiconductor device manufacturing process. Among various types of equipment used for this purpose, the thin film X-ray diffractometer employs an optical system (Fig. 1) specifically designed for the studies of thin films that are relevant to recent new materials. This diffractometer therefore allows measurement of thin film samples. The measurement has hitherto been considered impracticable. Generally, when the sample thickness becomes less than 1000nm the number of crystal lattices that contribute to X-ray diffraction will decrease resulting in a drastic reduction in the Xray diffraction intensity and a rise of the background. To cope with this, the thin film diffractometer is so designed that the incident X-rays are fixed at a small angle of 3° to 5° so as to lengthen the optical path along which the X-ray beam passes through the thin film. This increases the X-ray diffraction intensities. Also, a monochromator is mounted in front of the detector in order to reflect only the diffracted X-rays, to remove scattered X-rays emitted from the sample and to reduce the background. As a measurement example, Fig. 2 shows a diffraction pattern of a sample formed by deposition of a 10 nm Au thin film on a Si single crystal substrate. As examples of applications to the semiconductor field, Fig. 3 and Photo 1 show data obtained with the reflection method small angle scattering goniometer and with the double crystal topographic camera (listed in Table 1) respectively.