Electrical properties of cobalt and copper contamination in processed silicon

The issue of detection and migration of metal contamination during Si wafer processing is crucial for the perfection of 0.18 mum manufacturing technology. In these experiments, both Co and Cu were intentionally introduced into Si wafers by two methods: either 1 MeV or 60 keV ion implantation at doses of 1 x 10(11) cm(-2) to 1 x 10(13) cm(-2), or by dipping into a standard Co solution. Quantox, secondary ion mass spectroscopy, total X-ray fluorescence, and deep level transient spectroscopy were used to analyze metal migration during furnace heat-treatments. Both Co and Cu diffused from the back of the wafers to kill carrier recombination lifetime throughout the bulk Si. p/p(+) epitaxial gettered the Co, so near-surface lifetime remained high even after contamination. Co diffused through 40, 100, or 1000 Angstrom SiO2 into the bulk of Si. However, there was no evidence of Co migration from the surface of wafers to adjoining wafers during furnace anneal, 900 degreesC, 30 min. Measurements of charge-to-breakdown, Q(bd), on fabricated metal oxide semiconductor poly-dots before and after Cu and Co back-side implant and annealing at either 650 or 1000 degreesC, 30 min, showed no changes attributed to metals within the 100 Angstrom oxides. In addition, metal contamination, introduced either by implantation into the Si or by deposition on the oxide at these levels, did not effect interface state density, D-it, or oxide tunneling voltages. (C) 2001 The Electrochemical Society.