Low temperature plasma-assisted wafer bonding and bond-interface stress characterization

This paper presents the development and characterization of a low temperature plasma-assisted direct wafer bonding process for structured silicon wafer pairs. We have achieved spontaneous bonding at room temperature with a surface energy of up to 1.2 J/m/sup 2/. It turned out that the bonding process is not deteriorated by the history of the wafers, even after etching for several hours. The yield of the process is 80-95%. A blister test was used to determine the bond strength and the failure distribution for different plasma gases and annealing treatments. Film stress of the bonded interfacial oxide was found to transfer to the bonding partner. Selective wafer bonding was made by structuring the interfacial oxide layer. Design rules for proper bonding are given.