Morphology and Bond Strength of Copper Wafer Bonding

The morphology and bond strength of copper-bonded wafer pairs prepared under different bonding/annealing temperatures and durations are presented. The interfacial morphology was examined by transmission electron microscopy while the bond strength was examined from a diesaw test. Physical mechanisms explaining the different roles of postbonding anneals at temperatures above and below 300°C are discussed. A map summarizing these results provides a useful reference on process conditions suitable for actual microelectronics fabrication and three-dimensional integrated circuits based on Cu wafer bonding.