Atomic diffusion bonding of quartz glass wafers using thin Ti films, with SiO2 underlayers on wafer surfaces, provides 100% light transmittance at the bonded interface along with strong bonding energy, after post-bonded low-temperature annealing. Cross-section images obtained using transmission electron microscopy show that the bonded interface after annealing at 350 °C consists of amorphous structure including nanocrystalline grains. Structural analysis using electron energy loss spectroscopy shows that post-bonded annealing enhances oxidation of Ti with oxygen dissociated from SiO2 underlayers, and that Ti oxides form close to TiO2 or Ti4O7. This oxidation provides 100% light transmittance with high bonding strength attributable to the annealing. Moreover, we applied this technique for bonding glass and sapphire wafers using SiO2-Nb2O5 underlayers, demonstrating that 100% light transmittance and control of refractive index matching are achieved simultaneously at the bonded interface.
ASJC Scopus subject areas
- Physics and Astronomy(all)