Combined ultrasonic vibration and chemical mechanical polishing of copper substrates

This paper introduces an ultrasonic, vibration-assisted, chemical mechanical polishing (UV-CMP) method and an ultrasonic, vibration-assisted, traditional diamond disk (UV-TDD) dressing method. A copper substrate is polished by traditional CMP and UV-CMP. UV-CMP combines the functions of traditional CMP and ultrasonic machining (USM) with small-amplitude, high-frequency tool vibration to improve the fabrication process and machining efficiency. The removal rate of the copper substrate, torque force, and polished surface morphology of CMP and UV-CMP are compared. The polishing pad is also dressed by traditional diamond disk (TDD) and UV-TDD. The pad cut rate, torque force, and pad surface profiles of TDD and UV-TDD are also investigated in experiments. Experimental results reveal that UV-TDD can produce twice the pad cut rate and reduce torque force compared to TDD. Consequently, a dressing time reduction by half is expected, and hence, the diamond life is extended. It is found that the removal rate of the copper substrate polished by UV-CMP is increased by approximately 50–90% relative to that of traditional CMP because in UV-CMP, a passive layer on the copper surface, formed by the chemical action of the slurry, will be removed not only by the mechanical action of CMP but also by ultrasonic action. In addition, the surface roughness improves and the torque force reduces dramatically. This result suggests that the combination processes of CMP/USM and TDD/USM are feasible methods for improving polishing and dressing efficiency.

► We introduce an ultrasonic assisted chemical mechanical polishing (UV-CMP) method.
► An ultrasonic assisted diamond disk (UV-TDD) dressing method is also studied.
► UV-TDD can produce twice the pad cut rate.
► UV-CMP can increase the material removal rate by 50–90%.
► They are feasible methods for improving polishing and dressing efficiency.