Low Temperature Fusion Bonding of Glass to Si Using Plasma Activation

Anodic bonding has been extensively used to permanently bond glass to silicon (Si) wafer for MEMS (microelectromechanical systems)-based sensor applications. This approach involves the alkali ion migration (such as Li, Na, and K) under high-temperature, high pressure, and high voltage. Moreover, similar coefficients of thermal expansion (CTE) are required to bond these two heterogeneous substrates over a wide range of temperatures. However, some active or passive devices in MEMS are temperature sensitive and those alkali ions from glass could exhibit undesirable side effects to degrade the device performance when subjected to moisture and heat. The low-temperature direct bonding processes for an alkali-free glass wafer to another Si wafer hence has been studied recently.