Intermetallic Cu3Sn as oxidation barrier for fluxless Cu-Sn bonding

Abstract

A fluxless Cu/Sn SLID bonding process was demonstrated by using intermetallic Cu3Sn layer as the oxidation barrier for Cu interconnects. Oxidation behavior of intermetallic Cu3Sn was confirmed by aging Cu and multilayer Cu/Cu3Sn films at elevated temperatures in ambient air, and measuring the oxidation level by energy dispersive x-ray microscopy (EDX). The strength of bonded interconnects were characterized by shear testing, and found to be comparable to conventionally SLID bonded interconnects. Furthermore, the interdiffusion process of elemental Cu and Sn in the bonding region is discussed.