Al/Au multilayers with different diffusion barrier layers for application as wafer-bonded UV reflectors

A room-temperature wafer bonding using Al/Au multi-layers with a Pt or an Al₂O₃ barrier layer has been demonstrated for wafer-bonded reflectors in the ultraviolet (UV) spectral region (200-400 nm). Surface activation prior to Au-Au room-temperature bonding was performed using argon radio-frequency plasma. Experimental results showed that the Al₂O₃ layer prevents the solid-state diffusion between Al and Au. A high reflectance of more than 80 % was obtained using the Al₂O₃ barrier layer in the UV spectral region.