Hot-forming of micro glass cavities for MEMS wafer level hermetic packaging

Hermetic or vacuum packaging to maintain a controllable cavity pressure and low costs are required by many MEMS devices having moving parts. In this paper we propose a hot-forming process of fabricating micro glass cavity arrays for wafer-level and hermetic packaging of MEMS. First, the principle of the hot-forming process was discussed. Then, the hot-forming process for preparing cavity arrays in Pyrex7740 glass wafer was studied experimentally. After that, edge wrinkling of hot-formed wafers, hermetic wafer-level packaging, singulation of the wafer level cavity arrays were discussed. Results show that wafer-level packaged cavities were prepared, whose diameter was controllably between 200 microns and 2000 microns. It is also found that the hot-forming temperature and the processing time affect the filling rate of the glass. Results also show that edge wrinkling of hot-formed wafer could be removed by lowering the hot-forming temperature. It is then revealed that singulation of bonded wafers was achieved by low-cost laser drilling. Results show that the leakage rate of the packaged cavity is below 5Χ10⁻⁹ Pa. m / s.