Development of reliable low temperature wafer level hermetic bonding using composite seal joint

A reliable composite metal seal comprising both intermetallic compounds (IMC) and solder joints, which are formed by transient liquid phase bonding and soldering respectively, is proposed and demonstrated in wafer level bonding experiments. Hermetic sealing is demonstrated on 8-in. wafers using low volume Cu/Sn materials at process temperatures as low as 280 °C. It is shown that the composite seal is stable when subjected to temperatures of 250 °C, and that it provides better hermeticity and reliability than an IMC seal alone.

► Composite seal composed of both IMC and solder joints for wafer bonding has been studied. ► Cu/Sn materials were used and wafer bonding was performed at 280 °C. ► Composite seal joint combines the advantages of both IMC and solder joint. ► Composite seal is stable when subjected to temperatures of 250 °C. ► Better hermeticity and reliability were achieved using composite seal compared with pure IMC seal.