Effect of surface roughness on void formation and intermetallic growth in electrodeposited Cu-Sn stacks

Abstract

Abstract Effect of surface roughness on the void formation and intermetallic compounds (IMCs) growth in the Cu-Sn diffusion layers is reported. Different samples having varying surface roughness of the electrodeposited copper were obtained by using different current densities, i.e., 5 mA/cm2 (type-I) and 50 mA/cm2 (type-II). Electrodeposited copper samples having higher surface roughness showed the formation of larger voids than the samples having a lower surface roughness, which was attributed to the larger peaks and lower availability of copper at the peaks. The mechanism for void formation and growth was also proposed with the experimental validation. The IMC growth was hampered in samples having higher copper surface roughness due to larger voids at Cu-Cu3Sn interface. The direct influence of underlying copper surface roughness on the void size, void fraction, and the IMC growth is experimentally demonstrated.