Low temperature bonding of wafers coated with low-κ dielectric film of carbon-doped oxide (CDO) is demonstrated. Direct bonding is successfully achieved by using oxygen plasma activation which modifies the low-κ CDO surface to be more hydrophilic. It is discovered that after a 300°C anneal in N2 ambient for 3 h, bond strength of the bonded wafer pair is enhanced by 33.8% from 1270 to 1700 mJ/m2 with oxygen plasma surface activation. This enhancement is attributed to reduction in carbon content at the bonding surface that increases the surface energy. Void growth is observed with post-bonding isothermal annealing and it can be suppressed with multistep annealing. Wafer bonding with low-κ dielectric is a promising choice to realize high density 3D IC for performance enhancement in future integrated circuits and systems.