Investigation of Au-Si eutectic wafer bonding for small-cavity MEMS devices

Purpose This study aims to present a reliable wafer-level Au-Si eutectic bonding technique that achieves good hermeticity and high vacuum for MEMS resonators with extremely small cavities (<0.01 mm³). Design/methodology/approach The Au-Si eutectic bonding was improved using Ti/Pt as the adhesion and barrier layers, significantly enhancing bonding quality. A microcantilever was packaged to evaluate the vacuum level in the small cavity. Findings The air damping was dramatically reduced for the packed microcantilevers and their quality factors (Q) increased from 600 in atmosphere to over 50,000, corresponding to the vacuum level below 3 Pa. Originality/value Therefore, this bonding technique is applicable for developing high-end MEMS devices.