Characteristics of chemical mechanical polishing using graphite impregnated pad

This paper introduces a new design for polishing pads that eliminates the need for built-in pores. Instead, a polyurethane matrix is impregnated with nanographite particles to form a graphite impregnated pad. The surface characteristics as well as the friction force, slurry flow rate, and material removal rate when polishing a dielectric oxide film were experimentally measured and compared with those for conventional porous polishing pads. The results reveal that the proposed pad has an approximately 40% lower dressing rate and consequently greater tool life. Further, use of the impregnated pad reduces slurry consumption as the removal rate at slurry flow rates of <100 ml/min is significantly higher than that for porous pads. The increased removal rate can be attributed to adsorption of slurry onto the large surface area of the nanographite particles. The results suggest interesting possibilities for significant reduction in the cost associated with CMP processing.