Energy-selective (+, +) monolithic monochromator and relative lattice-spacing measurement of Si wafers with synchrotron radiation
X-ray optic systems have been developed at beamline BL-3C2 of the Photon Factory, KEK, for the study of the relative lattice spacings of Si wafers using synchrotron radiation. Since synchrotron radiation has no characteristic (wavelength) spectral lines, unlike an X-ray tube, a new tool has been introduced into the system as a wavelength-selective device – a (+, +) high-resolution channel-cut monolithic monochromator. Using two types of monolithic monochromator, two schemes are proposed and applied to the study of the lattice spacings of Si wafers. The lattice-spacing differences are determined in the sub-p.p.m range; for example, in scheme 1 and scheme 2 we obtain 0.6 p.p.m. and 0.2 p.p.m., respectively. One of the practical advantages of this system is that it can be applied for a fast and precise measurement of the lattice-spacing changes due to the doping and defects in Si, GaAs and other single crystals.