Modeling of Polishing Regimes in Chemical Mechanical Polishing
- PDF / 107,280 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 6 Downloads / 233 Views
W5.9.1
Modeling of Polishing Regimes in Chemical Mechanical Polishing Suresh B. Yeruva1,3, Chang-Won Park2,3, Brij M. Moudgil1,3 Department of Materials Science and Engineering, 2 Department of Chemical Engineering, 3 Particle Engineering Research Center, University of Florida, Gainesville, FL 32611, U.S.A 1
ABSTRACT Chemical mechanical polishing (CMP) is widely used for local and global planarization of microelectronic devices. It has been demonstrated experimentally in the literature that the polishing performance is a result of the synergistic effect of both the chemicals and the particles involved in CMP. However, the fundamental mechanisms of material removal and the interactions of the chemical and mechanical effects are not well understood. A comprehensive model for CMP was developed taking into account both the chemical and mechanical effects for monodisperse slurries. The chemical aspect is attributed to the chemical modification of the surface layer due to slurry chemistry, whereas the mechanical aspect is introduced by indentation of particles into the modified layer and the substrate depending on the operating conditions. In this study, the model is extended to include the particle size and pad asperity distribution effects. The refined model not only predicts the overall removal rate but also the surface roughness of the polished wafer, which is an important factor in CMP. The predictions of the model show reasonable agreement with the experimental observations. INTRODUCTION Chemical mechanical polishing (CMP) is well-established technology for planarization of films at various stages of integrated circuit (IC) fabrication process. The process consists of wafer to be polished, polymer pad and an aqueous slurry of abrasive particles and chemicals. The rotating pad and wafer are pressed against each other, such that the two surfaces move relative to each other. The slurry chemicals interact with wafer surface to form a chemically modified layer, whereas the abrasive particles, trapped between wafer and pad, remove this surface modified layer. An ideal CMP process is tailored to produce high removal rate, excellent global planarity, low surface defectivity, and high selectivity with respect to the underlying layers. Although the technology has developed rapidly in recent years, understanding of the fundamental chemical and mechanical processes involved is inadequate. A CMP system involves many variables that need to be optimized, including tool parameters (force applied, pad-wafer relative velocity, etc.), wafer parameters (wafer material properties, pattern density, etc.), slurry variables (particle size distribution, chemistry, flow rate etc.) and pad variables (hardness, roughness, conditioning etc.). Better control of a CMP process demands detailed understanding of the role played by each of the parameters involved and the interactions between them. The Preston equation as an empirical relation for optical glass polishing was substantiated by Cook[1] who considered that the interaction between abrasi
Data Loading...
