Time-dependent surface properties and wafer bonding of O-2-plasma-treated sillicon (100) surfaces

Low-temperature wafer direct bonding is considered a key tool for the fabri cation of bulk micromechanic devices. The possibility of enhancing the bond ing energy by applying an O-2 plasma treatment before bonding has been the focus of recent studies. Here, the effect of storage following the plasma t reatment, as well as the duration of the latter on the attainable activatio n of the surface, the bonding strength, and bubble generation, have been in vestigated. Immediately after the plasma treatment bond energies up to 1.6 J/m(2) are achieved. However, 50 h after the treatment bonded wafer pairs s how bonding energies up to only 1.3 J/m(2). The duration of the plasma trea tment strongly affects the number, size, and distribution of interface bubb les. (C) 2000 The Electrochemical Society. S0013-4651(99)08-103-3. All righ ts reserved.