Investigation of Copper Removal Mechanisms during CMP

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Abstract
In this paper we continue our (CMP) of copper mechanism study of the chemical mechanical polishing using a novel experimental approach. We investigated the effects of chemical reagents in the polishing slurry on the removal behavior of copper film during its CMP. More specifically, the friction and wear of the copper surface against a polyurethane pad were measured in the presence of slurries containing various chemical constituents and surface-treated abrasive particles. These slurries are typically formulated for Cu CMP in the industry. The surface qualities and wear mechanisms were then investigated using an atomic force microscope. The experimental results indicate that the copper removal mechanism in the presence of an abrasive and DI water alone was dominated by mechanical abrasion, while chemical dissolution of copper is much more pronounced when the slurry was added a complexing agent such as glycine, regardless the involvement of the strong oxidizer hydrogen peroxide. In the presence of a slurry consisting of hydrogen peroxide, glycine, and nanometer-sized silica particles, a series of electrochemical reactions promotes the rapid formation of copper oxide and the redeposition of Cu(OH)2Cu(OH)2 precipitation. Based on these tribological investigations we attempt to describe the nature of the material removal, which is one of the key unanswered questions in the CMP community. © 2004 The Electrochemical Society. All rights reserved.

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