Study On The Application Of Wafer-level Hermetic Package Of MEMS By Glass Frit At Low Temperature

Wafer bonding is an essential technological step for wafer level encapsulation of sensitive structures like freely moveable MEMS. In the last years, different wafer bonding technology established in research and in industrial production processes. These wafer bonding steps have to be adapted to the special application or the technology environment. Therefore we were looking for a bonding technology, which is universally useable for a wide range of applications, independent on preceding process steps and design variations. Glass frit wafer bonding fulfils these requirements and provides furthermore a safe process with high bonding yield, very well suitable for industrial production.This paper reports on glass frit wafer bonding. A cap wafer is bonded to the device wafer using a pre-solidified frit glass as a bonding medium such that the devices are hermetically sealed inside the cavities. A optimized process profile such as temperature and press can be get from series of experiments. Shear test and leakage test are performed to investigate the bonding strength of the sealing structure and the hermiticity of the encapsulation. The results prove that the leakage and bonding strength fulfill the corresponding MIL-STD-883E standard.Vacuum package is an application of hermetic package. A high-performance in-plane-sensitive sidewall-piezoresistive accelerometer is used to investigate the vacuum quality. We measure the quality factor Q of device to scale the pressure of the cavity and monitor the vacuum situation in a long term.