Characterization and Qualification of Wafer-Bonded MEMS Devices

In this paper characterization and qualification methods of wafer- bonded MEMS devices are introduced. The main focus is on stud pull tests for bond strength measurement in real MEMS chips, in combination with a statistical Weibull diagram evaluation. The stud pull test covers all strength-related aspects from wafer bonding and dicing as well as from the whole wafer process and final dicing. Based on the results of this test, it was possible to optimize the wafer bonding quality regarding strength, and subsequently it was used to qualify the reliability of different wafer bonding techniques in complete MEMS technologies. In addition, the hermeticity of the wafer-bonding interface was tested and qualified by assessing the functionality of MEMS devices requiring hermetic sealing of a low pressure or vacuum.