Cavity-Through Deep Reactive Ion Etching of Directly-Bonded Silicon Wafers

Etched silicon wafers were directly bonded, and then the bonded silicon wafers were deeply etched by Bosch process through etched cavities. This cavity-through DRIE (deep reactive ion etching) was investigated after systematic study on plasma-assisted silicon direct bonding. The first half of this paper mainly reports the generation of voids in wafers directly bonded with N₂ or O₂ plasma treatment due to H₂O release from hydroxy groups in low and high temperature annealing. The second half reports etch profiles and etch rates for cavity-through DRIE using different recipes. Cavity-through DRIE in conjunction with silicon direct bonding is practical and useful for multi-layer MEMS.