The Compatibility of Copper CMP Slurries with CMP Requirements

Abstract

Cu is currently used as a replacement for aluminum in IC interconnections. One of the challenges of integrated circuit (IC) interconnection technology is the planarization process that involves fine copper lines patterning; the most perspective technique for Cu lines patterning is chemical mechanical planarization (CMP). CMP is applicable only once a given metal-slurry system can provide certain requirements. Different media, such as ammonium hydroxide peroxide ferric nitrite and nitric acid with and without the presence of inhibitors, were suggested as potential candidates for copper CMP slurries. In this work we studied the compatibility of these media with CMP requirements. Our work indicated that these slurry solutions (basic and acidic media) do not provide sufficient conditions for a conventional CMP application. The Cu is actively dissolved in all of these solutions and in some of them with high dissolution rate, without a rapid repassivation. The sharp acceleration in Cu etching rate under abrasive abrading can be attributed only to a mechanical Cu removal. It was found that the active dissolution of Cu is conducted through deep intergranular penetrations which may result in the deterioration of thin Cu connectors. This study also shows that the use of benzotriazole or other inhibitors commonly used for reducing the etching rate of the actively dissolved Cu cannot provide the needed conditions for a rapid passive film growth on the copper metal. The electrochemical behavior of Cu in these solutions, morphology of dissolved copper metal surface, and mechanism of copper CMP are discussed. © 2003 The Electrochemical Society. All rights reserved.