Room-temperature wafer bonding of silicon and lithium niobate by means of argon-beam surface activation

We have developed a method to bond silicon and piezoelectric ceramics wafers at room temperature. In the method, the wafers are bonded in vacuum after sputter etching by argon beam. It is not necessary to apply high pressure to force two specimens together in the bonding process. A 3-inch single crystal lithium niobate wafers was successfully bonded to a 4-inch silicon wafer. The bonding was so strong that fracture from the bulk material was observed after tensile tests. It is supposed that the argon-beam etching removes contaminant layers on the surface and surface atoms become in an active state, which is important for the strong bond formation at room temperature. This bonding method provides very low damage integration between silicon and piezoelectric materials such as lithium niobate.