Multilayer nano-thickness measurement by a portable low-power Bremsstrahlung X-ray reflectometer

Abstract

A low-power (1.5 W) portable Bremsstrahlung X-ray reflectometer (XRR) has been designed, realised and tested. The purpose of this apparatus is to measure thicknesses of multilayers within an X-ray beam energy range of 1–9.5 keV in industrial and research environments. Experiments have been carried out in this range with a measurement time of 10 min. The reflectometer apparatus was set up aligning the X-ray tube, sample holder and Si-PIN detector in one plane. A Mo/Si (9.98 nm) multilayer sample was used in the measurement. The direct beam intensity at (0.00°) was measured. Intensity was measured at several glancing angles and reflectivity was calculated. Although one measurement is sufficient in a dispersive energy X-ray reflectometer (XRR), measurement was taken at 0.45°, 0.60° and 0.80°. The sample was tilted at an angle θ and the detector was linearly elevated corresponding to 2θ at each measurement. A calibration equation was proposed to fit the apparatus geometry. Experimental reflectivity was calculated and compared to theoretical results. The portable X-ray reflectometer (XRR) was proved feasible in multilayer nano-thickness measurement.