Fluorescence Correlation Spectroscopic Investigation of Surface Adsorption of CMP Slurry Additives on Abrasive Particles
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Fluorescence Correlation Spectroscopic Investigation of Surface Adsorption of CMP Slurry Additives on Abrasive Particles Ashley E. Wayman1, Daniel K. Turner1, Ashwani Rawat2, Colin T. Carver3, Mansour Moinpour2 and Edward E. Remsen1 1
Mund-Lagowski Department of Chemistry and Biochemistry, Bradley University, Peoria, IL 61625, U.S.A. 2 Fab Materials Operation, Intel Corporation, Santa Clara, CA 95052, U.S.A. 3 Components Research, Intel Corporation, Hillsboro, OR 97124, U.S.A. ABSTRACT Additive-abrasive interactions in chemical-mechanical planarization (CMP) slurries are investigated using fluorescence correlation spectroscopy (FCS). The FCS technique provides quantitative determinations of the interaction between additives and abrasive particles by characterizing the competitive adsorption of the additive and a fluorescent probe molecule by an abrasive particle. Adsorption of the CMP additives glycine and benzotriazole (BTA) on precipitated and sol-gel colloidal silica abrasives are characterized. Significant differences in the fluorescent probe’s adsorption to the different silica abrasives in the presence of the additives suggest surface chemistry differences between the different types of silica. Extensions of the analysis of FCS data are proposed for improving the quantitative determination of the competitive adsorption of fluorescent probe dyes and CMP additives on abrasive particles. INTRODUCTION The application of chemical-mechanical planarization (CMP) processes in the production of integrated circuits depends on the manipulation of specific molecular interactions among the components in CMP slurries. For example, enhanced reactivity of small-molecule slurry additives driving chemical etching processes in CMP has been attributed to the transport of adsorbed additives on abrasive particles to a wafer surface [1,2]. Adsorptive interactions between abrasive particles and slurry additives are the product of familiar intermolecular forces such as hydrogen bonding, electrostatic interactions, and van der Waals forces. Detailed characterizations of additive adsorption at abrasive particle surfaces, therefore, provide a molecular foundation on which CMP slurries may be designed with optimized polishing performance. In this study, a single-molecule spectroscopic technique, fluorescence correlation spectroscopy (FCS) [3], is applied in the quantitative analysis of the adsorption of slurry additives on colloidal silica abrasive particles. Representative examples demonstrate the general applicability of FCS in the study of interactions between abrasive particle interactions and smallmolecule additives used in CMP slurries.
EXPERIMENTAL FCS experiments were performed using a custom-built system based on a Zeiss Axiovert Model 200 confocal inverted fluorescence microscope described previously [4]. All colloidal silica samples used were from commercially available sources and were provided by Intel Corporation. Alexa Fluor 546 carboxylic acid succinimidyl ester (>95% purity) was purchased from Life Technologies (Grand
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