Cu contamination control is critically important in Cu interconnect device manufacturing lines. The frontside gas protected spin cleaning enables the effective removal of the Cu contaminant from the backside and bevel of a wafer. A small area on the bevel was measured for cleaning efficiency using SOR (Synchrotron Orbital Radiation) X-ray fluorescence. The atomic level Cu removal was detected on the bevel surface with the barrier metal Ta existing wafers. The high energy SOR X-ray analysis makes it possible to measure the Cu contamination, where conventional methods do not work.