Sorry for a bit late reply, was fully charged last days with a flux clean tool issue at ATKL (Arik product lots on hold and production down). Looking to the differentiated AES spectra, the identification looks ok to me and believe the Cl is detected indeed. Have no AES history of Cl presence on Cu matrix, we normally do AES BP characterization on the Al and Cl should not be there (and only seldom detected). But that is for Al matrix. From TOF-SIMS however, we often see Cl in conjunction with Cu, but the detected Cl is hard to quantify and you need to keep in mind TOF-SIMS is over 1000x more sensitive. On itself I am not surprised to see Cl traces at the Cu.