A metallic dopant element having a greater oxygen-affinity than copper is introduced into, and/or over, surface portions of copper-based metal pads and/or surfaces of a dielectric material layer embedding the copper-based metal pads in each of two substrates to be subsequently bonded. A dopant-metal silicate layer may be formed at the interface between the two substrates to contact portions of metal pads not in contact with a surface of another metal pad, thereby functioning as an oxygen barrier layer, and optionally as an adhesion material layer. A dopant metal rich portion may be formed in peripheral portions of the metal pads in contact with the dopant-metal silicate layer. A dopant-metal oxide portion may be formed in peripheral portions of the metal pads that are not in contact with a dopant-metal silicate layer.