X-ray reflectometry (XRR) is one of the most powerful techniques to evaluate structures of thin and multilayered film materials. In Japan, certified reference materials of thin film and superlattice have been developed using a SI traceable XRR. In order to realize XRR with SI traceability, establishing an angle calibration system for the goniometer and accurate uncertainty evalutation method were essential. Reflectance correction method using an X-ray tracing technique has been developed in order to reduce uncertainty caused by surface flatness of specimens. Although XRR profiles obtained from the same specimen with different surface flatnesses did not agree, they agreed very well by using reflectance correction. The agreement of fitting results after reflectance correction was comparable to a repeatability of XRR.
