Anodic and direct bonding of Si and glass - Similarities and distinctions in applications

Wafer bonding is an enabling technology in substrate engineering, MEMS manufacturing and packaging as well as for hybrid integration of MEMS and CMOS. The mainstream semiconductor industry is currently exploring wafer bonding as a possible technology for 3D integration of IC devices. Several Bonding Processes exist today and can be classified under different aspects. They can be more or less well controlled and have been established in volume production of MEMS devices. Cost is still a critical factor, but sometimes there are no alternatives to wafer bonding to ensure the device functionality. Among many bonding processes with intermediate layers there are only two processes not using intermediate layers, the anodic and direct bonding. In this paper these two processes of bonding Silicon to glass wafers, are compared in some details. Equipment, process flow as well variations and modifications of the basically described processes are explained and discussed.