Enhancement of adhesion strength of Cu seed layer with different thickness in Cu/low-k multilevel interconnects

Abstract

Cu seed layer deposited with two different thicknesses, and subsequent annealing to enhance the adhesion strength to avoid peeling and delamination in Cu/low-dielectric constant multilevel interconnects were investigated. Emphasis was laid on the relation between thermal stability of Cu seeds at low and high annealing temperatures of 100 and 300°C, respectively, with seed thicknesses below 1000 Å. The impact on adhesion strength and the microstructure evolution of coupling effect of thin Cu seed layers and low annealing temperatures were also studied. Minimal agglomeration of the Cu seed layer and stronger bonding at the Ta/Cu interfaces, was observed, which indicated higher reliability for Cu damascene structure .