Formation of silicon structures by plasma-activated wafer bonding

A room temperature wafer bonding process based on oxygen plasma treatment or argon plasma treatment has been studied for surfaces of silicon, silicon dioxide, and crystalline quartz. The surface energy of the bonded samples was observed at different storage times. Atomic force microscope measurements, multiple internal reflection infrared spectroscopy, electrical characterization, secondary ion mass spectroscopy, and post-processing steps were performed to evaluate the plasma-treated surfaces and the formed bonded interfaces. Electrical measurements were used to investigate the usefulness of plasma-bonded interfaces for electronic devices. The bonded interfaces exhibit high surface energies, comparable to what can be achieved with annealing steps in the range of 600-800 degrees C using normal wet chemical activation before bonding. The high mechanical stability obtained after bonding at room temperature is explained by an increased dynamic in water removal from the bonded interface allowing covalent bonds to be formed. (C) 2000 The Electrochemical Society.