BTA Free Alkaline Slurries Developed for Copper and Barrier CMP

Abstract

© The Author(s) 2015. Published by ECS. With the technology node moving down to below 32 nm, ultra low k materials are routinely used currently. Integration of low k materials in the backend presents challenges in metal CMP processes. This paper reports the development of the alkaline slurries containing a novel additive that can be used for primary and secondary Cu CMP as well as barrier CMP. The slurries exhibited a relatively high removal rate in Cu CMP, especially at low polish pressure, because of the strong affinity between copper and functional groups in the additive. The smooth Cu surface with sub-nanometer roughness can be obtained with the Cu slurries plus the nonionic surfactant, BRIJ30. The Cu CMP slurries bring about satisfactory results of dishing and oxide erosion in the experiments. The k value of the low k material does not show significant difference after CMP with the barrier slurry. Since the slurries are free of BTA, it will be beneficial for post CMP cleaning of wafers. The low leakage current in the electric test could be attributed to the low level of metal contamination because of unique complexing action of the chelator.