A novel method for bonding of ionic wafers

A novel method for bonding sapphire, LiNbO₃, quartz and glass wafers with silicon using the modified surface activated bonding (SAB) method is described. In this method, the mating surfaces were cleaned and nano-adhesion Fe layers were deposited using a low energy argon ion beam simultaneously. The optical images show that the entire area of 4-inch wafers of LiNbO₃/Si was bonded. Such images for other samples show particle induced voids across the interface. The average tensile strength for all of the mating pairs was much higher than 10 MPa. Prolonged irradiation reduces polarization in LiNbO₃ , sapphire, quartz and Al-silicate glasses. Fe and Ar ions induced charge deposition may have resulted in electric field, which was responsible for the depolarization. The lattice mismatch induced local strain was found in LiNbO₃/Si. No such strain was observed in the Al-silicate glass/Si interface probably because of annealing at 573 K for 8 h. The Al-silicate glass/Si interface showed a layer of 2-nm thick. An amorphous layer of 5-nm thick was observed with a layer across the LiNbO₃/Si interface. The EELS spectra confirmed the presence of nano-adhesion Fe layers across the interface. These Fe layers associated with the electric filed induced by ion beam irradiation for prolonged period of time, particularly in Si/LiNbO₃ , might be responsible for the high bonding strength between Si/ionic wafers at low temperature