Improved adhesion of metal electrode layer on Si₃N₄ substrate through an all-wet process

Electroless deposition requires preliminary surface treatment to effectively adsorb a metal electrode layer onto a ceramic substrate. Herein, a simple surface treatment using an all-wet process was performed to achieve adhesion stability between a Si₃N₄ substrate and Ni film. The method involved deposition of an interfacial Pd-TiO₂ buffer between the two layers. Surface pretreatment via silanization was initially performed to improve surface wettability, thereby enhancing uniform deposition of Pd-TiO₂. Subsequently, a thin Ni layer was directly deposited onto the Pd-TiO₂ layer without necessitating sensitization or activation. The synthesized Ni/PdTiO₂/Si₃N₄ heat sink exhibited excellent adhesion property in the cross-hatch, scratch, and thermal shock tests. The mechanism of adhesion enhancement involved chemical bonding of Pd-TiO₂ with the self-assembled monolayer on the substrate and reduced internal stress due to removal of residual hydrogen between the layers of the heat sink. Thus, the fabricated heat sink has a promising application in electronic devices operated at high temperatures.