Annealing effect of surface-activated bonded diamond/Si interface

From transmission electron microscope (TEM) observation, a 25 nm thick amorphous layer was confirmed at the diamond/Si bonding interface without annealing, the amorphous layer thickness decreased with the annealing temperature. No cracking even in nanometer scale occurred even after high-temperature annealing at 800 °C. From in-situ micro-Raman monitoring, the compressed stress was observed in the Si of the bonding interface without annealing with respect to the bonding Si substrate. A tensile stress relaxation was observed in the diamond of the bonding interface with respect to the polished diamond. These results were attributed to the large load applied to the diamond and Si substrates during bonding process. After annealing at 400 °C, the residual stress in the Si of the bonding interface decreased, while the residual stress in the diamond of the bonding interface increased, which should be due to the residual stress caused by the applied load was released by annealing process. The residual stress in the Si and diamond of the bonding interface increased and decreased, respectively, as the annealing temperature increased from 400 to 1000 °C. The main reason was due to the structure change of the amorphous layer and the tensile stress relaxation in the diamond of the bonding interface.