Void-free strong bonding of surface activated silicon wafers from room temperature to annealing at 600 °C

In order to investigate the high temperature application of surface activated silicon/silicon wafer bonding, the wafers were bonded at room temperature and annealed up to 600 °C followed by optical, electrical, mechanical and nanostructure characterization of the interface. Void-free interface with high bonding strength was observed that was independent of the annealing temperature. The bonding strength was as high as 20 MPa. The normalized interfacial current density was increased with the increase in the annealing temperature. A thin interfacial amorphous layer with a thickness of 8.3 nm was found before annealing, which was diminished at 600 °C. A correlation between the current density and nanostructure of the interface was observed as a function of the annealing temperature. The high quality silicon/silicon bonding indicates its potential use not only in low temperature microelectronic applications, but also in high temperature harsh environments.