Combined Surface-Activated Bonding Technique for Low-Temperature Cu/SiO2 Hybrid Bonding
This work develops a combined surface-activated bonding (SAB) technique for low-temperature Cu/SiO2 hybrid bonding at below 200 °C. The technique involves combinations of Ar beam bombardment, Si deposition, and water vapor exposure for prebonding surface activation prior to bonding in vacuum. Homogeneous (i.e., SiO2-SiO2 and Cu-Cu) and heterogeneous (i.e., Cu-SiO2) wafer bonding were carried out with the same bonding technique. Surface properties of the surface-activated wafers have been investigated using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). Bonding strength has been measured by crack-opening method and tensile test. Bonding interfaces have been inspected by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Mechanisms of prebonding surface activation and bonding interface evolution during low-temperature postbonding annealing are discussed based on our results.