Gettering phenomena in directly bonded silicon wafers
Gold and copper gettering was investigated near the bonding interface of directly bonded silicon wafers. Boron-doped (100) float-zone silicon wafers were rotationally misoriented against each other by 1$DGR, 25° or 6$DGR, and then bonded and annealed at 1100°C for 2 hours. Then a thin film of gold copper was deposited on only one side of the bonded wafers, and annealed for 3 hours at 950°C and 1000°C for gold diffusion, and 900°C and 1100°C for copper diffusion. Spreading resistance measurements and transmission electron microscope were used, respectively, to check for gettering phenomena of gold and copper. The results showed that the gold concentration had increased, and that copper had precipitated near the bonding interface. These results indicate that the bonding interface of bonded wafers can provide gettering sites for metallic impurities and can therefore be used for introducing a gettering layer at a controlled distance from the active device region.
