Room-temperature Hermetic Packaging Using Ultrasonic Cu?Cu Bonding with Compliant Rim

In this paper, hermetic packaging using room-temperature (RT) Cu?Cu bonding is demonstrated for microsystem packaging. The bonding of the compliant rim made of Cu to electroplated Cu was performed with ultrasonic assist at RT. Owing to the cone-shaped cross section of the compliant rim, it easily deforms under pressing load with ultrasonic assist and bonds to the counter Cu film at RT. As a result of a simple vacuum test, the air leak rate of the cavity inside the bonded sample was approximately 2 ?~ 10?11 Pa?m3/s, which may be sufficiently low for applications of vacuum packaging of microdevices.