Ti concentration effect on adhesive energy at Cu/TiW interface

Changes in adhesive energy at Cu/TiW interfaces caused by varying the Ti concentration were evaluated by means of contact angle measurement. The adhesive energy was evaluated by applying the Young–Dupré equation to the contact angle. Copper particles were fabricated by annealing thin Cu film deposited on the TiW film. The adhesive energies at the Cu/TiW interface were evaluated as 1.5, 2.1, and 2.6 N/m for a Ti concentration of 0, 10, and 20 wt. %, respectively. The adhesive energies were found to increase almost linearly as the Ti concentration was increased. These results were applied to prevent TiW/Cu/TiW interconnects fabricated by using infrared-assisted reactive ion etching from peeling at the Cu/TiW interface. In annealing Cu films on TiW substrates at 600 °C in a vacuum, it was found that the Cu peeled from the TiW when the Ti concentration was 10 wt. %, but it stuck to that at 20 wt. %. The effect of Ti on the adhesion strength was also studied from the results of molecular calculation by using the method.