Evaluation of the bond quality of laser-joined sapphire wafers using a fresnoite-glass sealant

Two sapphire substrates were bonded using a fresnoite glass thin film as a sealant, by irradiation with a 1,064 nm ns laser. The sapphire close to the interface was examined by TEM, showing some structural defects due to the laser processing. Bond quality and strength were evaluated by scanning acoustic microscopy (SAM) and micro-chevron testing, respectively. Optimization of laser parameters lead to an improved processing speed (>1 mm/s) as well as an enhanced fracture toughness to 1.23 MPa m1/2.