Reliable hermetic MEMS chip-scale packaging

Reliable hermetic MEMS chip-scale packaging has been developed and tested with gold-tin soldering on 2×1.5 mm² chips. The test vehicle configuration consists of a glass cap with AuSn solder ring bonded onto a silicon resonator dummy chip. Through careful chip layout, UBM layer improvements and soldering process optimization, the shear tests yielded forces above 5 kg on a bonding ring area of ~0.5 mm². With a resulting shear stress larger than 100 MPa it is now possible to address a wider application domain for vacuum-encapsulated MEMS, where highly reliable hermetic solutions are required. Promising applications of hermetic and reliable MEMS are found in the medical field and in the space domain where defect-free sealing is a must. In the consumer electronics domain, where time-to-market and cost reduction are key factors, development time can be shortened for extremely miniaturized packaged MEMS.