Plasma assisted room temperature bonding for MST

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 measured after different storage times at room temperature. After 24 h the bonded interfaces exhibit high surface energies, comparable to what can be achieved with annealing steps in the range of 600-800 degreesC using normal wet chemical activation before bonding Subsequent annealing of the bonded silicon/silicon samples caused substantial generation of voids while void generation did not occur in bonded silicon dioxide/silicon dioxide samples. The void generation is influenced by process parameters such as the chamber pressure and the coil. The silicon/silicon interfaces formed at room temperature show electrical properties comparable to those of bonded silicon/silicon interfaces formed using wet chemical activation and high temperature annealing. (C) 2001 Elsevier Science B.V. All rights reserved.