Surface copper contamination of as-received float-zone silicon wafers

As-received float-zone Si wafers from two major suppliers are shown to have surface Cu contamination at a level of ∼5×1011 atoms cm−2, detectable by both low-temperature photoluminescence and room-temperature x-ray fluorescence. The effects of selective chemical removal of Cu from, or Cu adsorption onto, the front or rear surfaces of wafers have demonstrated where the majority of the contamination resides, thereby revealing its possible origin.