Simple and low-temperature vacuum packaging process by using Au/Ta/Ti metal multilayer

A Au/Ta/Ti metal multilayer was developed to improve the high vacuum packaging process for microdevice fabrication. This study revealed that the wafer coated with the Au/Ta/Ti layer could form direct bonding and absorb residual gas. We investigated the effect of Ta layer thickness on the diffusion of Ti atoms. The Au/Ta/Ti metal multilayers were successfully bonded after a degassing process when the Ta barrier layer is thicker than 1.5 nm. Moreover, the Au/Ta/Ti metal film effectively absorbed the residual gas molecules by annealing at 350 °C. As the annealing temperature for the gas gettering is lower than the previous reports, the Au/Ta/Ti metal multilayer could be useful for the future vacuum packaging process.