Structural characterization of laser bonded sapphire wafers using a titanium absorber thin film

Two sapphire substrates were tightly bonded by irradiation with a 1064 nm nanosecond laser and using a sputtered 50 nm-titanium thin film as an absorbing medium. Upon laser irradiation, aluminum from the upper substrate is incorporated into the thin film, forming Ti-Al-O compounds. While the irradiated region becomes transparent, the bond quality was evaluated by scanning acoustic microscopy.