(Invited) Cu Surface Passivation with Self-Assembled Monolayer (SAM) and Its Application for Wafer Bonding at Moderately Low Temperature

Abstract

In this paper, low temperature (<300 oC) thermo-compression bonding of bump-less Cu-Cu in the context of 3D IC application is discussed. The Cu surface degradation is overcome by the application of a self-assembled monolayer (SAM) of alkane-thiol as a temporary passivation layer. This method is potentially attractive as it is non-UHV and non-corrosive. With SAM passivation, surface oxidation and contamination are controlled and upon SAM desorption, a cleaner Cu surface is available for bonding at low temperature. SAM passivated Cu shows higher degree of interdiffusion and grain growth during bonding. This results in the enhancement of the physical properties of the Cu-Cu bond which is potentially suitable for 3D IC stacking.