Wafer-Level Packaging for Micro-Electro-Mechanical Systems Using Surface Activated Bonding

摘要

Wafer-level packaging (WLP) is increasingly important for micro-electro-mechanical systems (MEMS) because of downsizing, cost reduction, and mechanical damage suppression during assembly. The diaphragms were fabricated using surface activated bonding (SAB), a room-temperature bonding, that realizes an accurate alignment, a low stress at a bonding interface, and a high throughput. Gaps and voids were not observed in acoustic microscopy images and in a transmission electron microscopy (TEM) cross-sectional image of the Si/Si interface. After dicing, the evaluations of the airtightness and stress of the interface were performed using a helium leak detector and a micro-Raman spectroscope, respectively. The stress was shown to be markedly lower than those of the anodic, and eutectic bonding. We demonstrated the low-stress and high-airtightness diaphragms of WLP using SAB. We showed that these technologies are very suitable for MEMS that require a low stress and a high airtightness, such as biosensors and mechanical sensors.