Effect of cobalt and copper contamination on the electrical properties of 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 1MeV or 60keV ion implantation at doses of 1x10(11)cm(-2) 1x10(13)cm(-2), or by dipping into a standard Co solution. Quantox, SIMS, TXRF, and DLTS 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 wafers and high energy B ion-implantation gettered the Co, so near surface lifetime remained high even after contamination. Co diffused through 40A, 100A, or 1000A SiO2 into bulk of Si. However, there was no evidence of Co migration from the surface of wafers to adjoining wafers during furnace anneal, 900C, 30 minutes. Measurements of Q(bd) On fabricated MOS poly-dots before and after Cu and Co backside implant and annealing at either 650C or 1000C, 30 min, showed no changes attributed to metals within the 100A oxides. In addition, metal contamination, introduced either by implantation into the Si or by deposition on the oxide at these levels, did not effect D-it or oxide tunneling voltages.