A Robust Wafer-Level Capping Approach for MEMS Devices

Micro-electromechanical systems (MEMS) devices are extremely sensitive to their environment, especially at wafer-level, until they are packaged in final form. The harsh back-end (BE) operations that the MEMS devices have to endure include dicing, pick-and-place, wire bonding and molding. During these processing steps, the MEMS device is exposed to particles and contaminants. Therefore, protection at an early stage is a fundamental requirement. In this work, we describe a silicon nitride thin-film capping, which is processed using a sacrificial layer technique only with front-end technology. This approach is suitable for mass production of MEMS devices, owing to the fact that, it is more cost-effective when compared to other approaches such as wafer-to-wafer bonding and die-to-wafer bonding. A Bulk Acoustic Wave (BAW) resonator, that finds application in the Radio Frequency (RF) front end, e.g., in cell phones, is taken as a MEMS vehicle for our work. It is an example of an extremely sensitive MEMS device,...