Selective Wafer Bonding by Surface Roughness Control

Selective wafer bonding is presented as a technique for fabrication of microelectromechanical systems (MEMS) devices with movable, contacting elements, e.g., micromachined valves. The selectivity of the wafer bonding is obtained by tailoring the wafer surface microroughness. The adhesion parameter is used as the design rule for the wafer bonding technique. The technique is demonstrated with bulk micromachined check valves and a pressure actuated normally closed valve, but can be used for fabricating MEMS devices using surface micromachining processes as well. For these valves the selective fusion bonding technique turned out to be a convenient way to bond different wafer layers and a promising fabrication step with a high, reliable product yield.