Nanoscale Indentation of Polymer and Composite Particles by Atomic Force Microscopy
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0942-W08-03
Nanoscale Indentation of Polymer and Composite Particles by Atomic Force Microscopy Silvia Armini1, Ivan U. Vakarelski2, Caroline M. Whelan3, Karen Maex4, and Ko Higashitani2 1 SPDT/AMPS/CMP, IMEC/KU Leuven, Kapeldreef, 75, Leuven, 3001, Belgium 2 Kyoto University-Katsura, Kyoto, 615-8510, Japan 3 SPDT/NANO, IMEC, Leuven, 3001, Belgium 4 KU Leuven, Leuven, 3001, Belgium
ABSTRACT Atomic Force Microscopy (AFM) was employed to probe the mechanical properties of surfacecharged polymethylmethacrylate (PMMA)-based terpolymer and a composite terpolymer coresilica shell nanosphere in air and water media. Since these materials exhibit enhanced mechanical properties, such as toughness and elasticity, and enhanced chemical stability, they are particularly interesting for potential applications in reducing defectivity during the process of Chemical Mechanical Planarization. The polymer particles were subjected to a thermal treatment aimed at improving their mechanical properties in terms of hardness (H) and elastic modulus (E). By analysis of force-displacement curves and on the basis of Hertz’s theory of contact mechanics, Young’s moduli were measured for the terpolymer compared with the composite that has expected mechanical property enhancement due to its silica shell. In air, E increases from 4.3 GPa to 6.6 GPa for the treated terpolymer compared with the respective value of 10.3 GPa measured for the composite. In water, E increases from 1.6 GPa to 4.5 GPa for the thermally treated terpolymer that is comparable with the respective value of 3.6 GPa measured for the composite. This observation suggests that as an alternative to the creation of polymer-silica composite nanoparticles for CMP, comparable mechanical properties can be achieved by a simple heat treatment step. INTRODUCTION The deformation of spherical particles under an external force is interesting for their ubiquitous applications in the food, pharmaceutical, coating, chemical, and microelectronic industry. In the field of microelectronics, one of the major applications of submicrometer colloidal particles, as abrasives in a slurry chemical composition, is in the Chemical Mechanical Polishing (CMP) process that is used to achieve planarization, i.e. smoothing the uneven topography of non-planar thin films of metals/dielectrics. A CMP system, comprising a polishing pad, appropriate slurry and a wafer surface, is influenced by many variables including tool process parameters, wafer-to-wafer variables, fluid dynamics, and slurry variables, such as hardness, roughness, and elastic modulus. While considerable progress has been made in identifying the role of the slurry chemistry [1], evaluation of the role of mechanical abrasion is complicated by the difficulty in establishing the relationship between the mechanical characteristics, such as hardness (H) and elastic modulus (E), of the abrasives and of the films being planarized [2]. The ability of AFM to probe local surface topography, elastic properties, and adhesive forces makes this technique ideal fo
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