Office of Technology Transfer – University of Michigan

A Method for Low-temperature Sealing of Microcavities at Wafer-Level

Technology #2111


Packaging is one of the most challenging and costly processes in the integrated circuits (IC) and sensor industry, and remains a bottleneck for IC commercialization. With moving components, the already challenging packaging task is complicated further for MEMS devices. Thus far, packaging methods reported in the literature are application-specific, and there is a lack of standardization in wafer level MEMS device packaging. Furthermore, high, unpredictable, residual pressures inside the cavity and vacuum degradation over time are major obstacles in packaging high-performance MEMS devices such as high-quality factor resonators and absolute pressure sensors.


University of Michigan researchers developed a post-packaging pressure control scheme integrated with a wafer-level packaging technique to compesnate for vacuum degradation. The approach provides an improved method and system for locally sealing a vacuum microcavity, monitoring and controlling pressure, and trimming resonant frequency of a microstructure. A consistent low base pressure is provided inside the vacuum microcavity, and the pressure in the microcavity is measured. When the pressure exceeds a maximum desired level, the pressure is reduced in response to compensate for vacuum degradation within the vacuum microcavity.

Applications and Advantages


  • Post-packaging pressure control/ wafer-level MEMS packaging


  • Reduced cost: system can be integrated and processed at wafer-level
  • Improved device performance and lifetime: minimized vacuum degradation
  • Flexible method: can be applied to many existing MEMS devices, compatible with various fabrication methods