Wafer-scale surface activated bonding of Cu-Cu, Cu-Si, and Cu-SiO 2 at low temperature

Wafer scale direct bonding of Cu-Cu, Cu-Si, and Cu-SiO2 was performed at low temperature using surface activated bonding (SAB) method. Successful direct bonding of Cu-Cu and Cu-Si was achieved at room temperature. However, bonding of Cu-SiO2 using SAB process at low temperature failed. In order to integrate Cu to SiO2, two-step surface activation process was adopted. The copper was exposed to Ar ion beam and SiO2 was exposed to oxygen plasma, respectively. In addition, the oxygen plasma-treated SiO2 were subsequently bombarded by Ar ion beam for 10 s prior to bonding. The two heterogeneously treated Cu and SiO2 surfaces were bonded at low temperatures. The bonding interface of Cu-Cu, Cu-Si, and Cu-SiO2 was evaluated by tensile pulling tests and transmission electron microscopy (TEM) observations.