Room-Temperature Wafer Bonding Using Al/Ti/Au Layers for Integrated Reflectors in the Ultraviolet Spectral Region

A room-temperature wafer bonding process using Al/Ti/Au multi-layers has been demonstrated for integrated reflectors in the ultraviolet (UV) spectral region. A glass wafer with Al (35 nm)/Ti (3 nm)/Au (15 nm) layers and the wafer with Ti (3 nm)/Au (15 nm) layers were successfully bonded in ambient air at room temperature after argon radio-frequency plasma activation process. A thin native aluminum oxide (Al2O3) layer was formed on the Al layer and was found to be effective in avoiding solid-state reactive diffusion between Au and Al. Interface reflectance of more than 80 % was obtained in the UV spectral region (200-400 nm).