Slurry size distribution, conductivity

Mahajan and coworkers [85] studied the impact of abrasive size at different particle concentrations on the oxide removal rate. It was found that the removal rate was a direct function of the particle concentration for monosize abrasives of size 0.2 pm, thereby supporting the contact-area mechanism. The mechanism shifted to indentation for a monodispersed system at 1.5 pm, resulting in reduced removal rates. At 0.5 pm, the removal rate initially increased and then decreased with particle concentration, suggesting a shift in the removal rate mechanism. Particle-size distribution [86] has an equally important effect as the particle size. A larger number of oversized particles in the distribution also cause a shift in the mechanism of material removal. Mahajan and coworkers conducted studies to evaluate the impact of size distribution on oxide removal rates. Baseline commercial slurry was spiked with different concentrations of impurities in the range of 0.5-1.5 pm. The size at different concentrations resulted in removal rates lower than that obtained with the original slurry. Slurry spiked with 1.1 % of 1.5pm particles resulted in a removal rate equal to the baseline slurry, suggesting the predominance of indentation mechanism. Slurries spiked with other concentrations and sizes resulted in a decrease in the removal rate explained by the reduction in the contact area of the abrasives with the oxide substrate. 

Polystyrene Latex (PSL) Bead Solution Filtration Experiments were conducted to obtain filter retention, flow rate, and Ap data for a DI water based PSL bead mix solution prepared using particles ranging from bead diameters of 0.772 to 20 pm. It is a common practice to use PSL bead challenge solutions (created by mixing different size PSL bead standards in specific volumetric ratio to simulate slurry-like particle size distribution for the bead mix solution) to obtain relative quantitative retention data for various filters. These solutions are expected to retain stable PSD and provide more consistent information compared to real CMP slurries, which may change particle characteristics over time. 

Complete and uniform dispersibility of fillers in a matrix is a prerequisite for a con )osite to have optimum properties. Regardless of conq>osition, shape or size of the particles, less than optimum distribution in, for exanq)le, ceramic, metal or polymer material can result in lower mechanical strength, random discoloration or decreased electrical or thermal conductivity. For these and other reasons much effort has been and continues to be devoted to understanding fundamental reasons why some powders readily disperse in a medium and others do not. It is clear from many historic studies (1-4) that the surface chemistry of a particle, which dictates relative hydrophilicity-hydrophobicity and zeta potential, is the dominant factor. Benefit of perfected filler dispemibility are found in dental resins (5), personal body armor (6), cosmetics and sunscreens (7), rubber products (5), latex paint (P), metal matrix conq)osites (10), inks and gels (11), many foods, and in abrasive slurries used for chemical mechanical planarization (CMP of wafers during con )uter chip manufacture (12),... 

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