CHARACTERIZATION OF SILICON WAFER SURFACES WITH SR-TXRF

2SEZ, Tokyo, Japan Total Reflection X-ray Fluorescence (TXRF) has proven itself to be a valuable tool for nondestructively detecting trace levels of metal contamination on silicon wafer surfaces. Such analyses have become crucial to the semiconductor industry as the levels of metal contamination that can be tolerated in the ultrathin gate dielectrics used in advanced processes have dropped to levels below 10 9 atoms/cm 2 . Furthermore, the implementation of Cu interconnect technology has further complicated the processing environment because of the possibility of cross contamination. This has resulted in a demand for better detection sensitivities together with a need to understand how metals deposit from solution onto the surfaces of the silicon wafers. This paper will describe the advanced capabilities provided by synchrotron radiation TXRF which achieve sensitivities about 50 times better than conventional instruments for transition metals, as well as millimeter scale spatial resolution allowing detailed elemental mapping of the entire wafer surface. In addition, by applying X-ray absorption near edge structure spectroscopy (XANES) in the TXRF geometry, it has been possible to determine the chemical state of atomically dispersed metal atoms and metal nanoparticles intentionally deposited on silicon surfaces from solution.