Charge densities at silicon interfaces prepared by wafer bonding

It is found that Si/Si and Si/SiO₂ interfaces exhibit different interface charge properties when bonded at comparable temperatures and surface treatments. Thermally grown oxides were bonded to bare silicon surfaces and the bonded Si/SiO₂ interface was investigated on MOS-structures by the C-V technique. Interfaces prepared at temperatures in the range 900-1100°c exhibited U-shaped interface state densities. Si/Si samples were prepared using a hydrophilizing surface treatment before wafer bonding. At the same annealing temperatures, the interface state densities of the bonded Si/Si interfaces were in the range 10¹¹-10¹³ cm^-2 eV^-1. Si/Si interfaces are found to be very sensitive to prebond chemical treatment, while Si/SiO₂ interfaces are not. Native oxides at bonded silicon interfaces have a more pronounced influence on Si/Si interfaces than on Si/SiO₂ interfaces