In this research, we conducted a series of experiments to investigate the mechanisms of chemical mechanical polishing (CMP) of silicon. Experimental approaches include tribological tests of frictional and lubricating behavior, chemical analysis, and surface characterization. Specifically, the effects of pH in slurry, surface roughness of wafers, and nano-particle size on removal rate were studied. A transmission electron microscope (TEM), a scanning electron microscope (SEM), and x-ray characterization tools were used to study the change of surface structure and chemistry. Experimental results indicate that the removal rate and planarization are dominated by the surface chemistry.
The determination method for analyzing trace copper in vanadium alloy by flame atomic absorption spectrometry was investigated in the paper. The sample digestion method, digestion acidity, determination conditions, matrix interferences, method precision, recovery of standard addition were investigated in detail. The method precision in RSD% was 8.6%, and the average recoveries of standard addition were from 93.9% to 95.6%. The experimental results indicated that the proposed method for determination of trace copper in vanadium alloy was simple, fast, accurate, and easy to operate, which was suitable for quality control of vanadium alloy.
A multi-scale method was developed, which utilized intrinsic relationships among zeta potential of particles, rheological properties of suspensions and particle size distribution (PSD), to analyze dispersion behavior of nanoparticles in concentrated suspensions. It was found that PSD of a kind of nanoceria particles by dynamic light scattering (DLS) method in solution A with concentration 5 wt% accorded well with that by direct TEM analysis, which meant the particles had been dispersed well. However, there had a significant difference when the concentration was increased to 20 wt%. When particles concentration increased from 5 wt% to 20 wt%, zeta potential in solution A changed from-150 mV to-100 mV, while zeta potential in solution B changed from-35mV to-45 mV. Variations of zeta potential of particles accorded well with rheological properties of suspensions too, from phenomenological models. When the suspensions composed by solution A and the nanoparticles with concentration about 20 wt% was diluted with its original solution to 5 wt%, the PSD of nanoceria could be measured indirectly, which accorded well with both that of a suspension prepared directly with near concentration and that from TEM images. Then a method to measure PSD of nanoparticles in concentrated suspension was brought forward.
The adsorption mechanisms of silicone rubber (SR)-stainless steel (SS) interfacial system and silicone rubber-HMX interfacial system were studied by molecular simulation method in the present paper. The molecular simulation results revealed that silicone rubber-stainless steel interface has obvious adsorption effect, while silicone rubber-HMX interface has certain adsorption effect. The systematic potential energy calculation results revealed that coulomb interaction and van de waals interaction might be the major microscopic adsorption mechanism for silicone rubber-stainless steel interfacial system and silicone rubber-HMX interfacial system.
The effect of compression storage on adsorption property of silicone rubber in silicone rubber-stainless steel interfacial system and silicone rubber-simulated X material interfacial system was studied in the paper by means of adsorption force testing and SEM statistical calculation method. The results of adsorption force testing indicated that surface roughness, sample type and compression ratio had important influence on adsorption, i.e. smooth surface tend to absorb, which implied that vacuum adsorption might be the main adsorption mechanism for silicone rubber interfacial systems. Plane-type, spherical type and inclinded plane type of samples had different degree of adsorption. Stainless steel interface tended to have larger adsorption than simulated X material interface. Higher compression ratio might lead to higher adsorption force. A SEM statistical calculation method was proposed to estimate the maximum vacuum adsorption force, and the maximum measurement result of adsorption force was approaching to the calculated maximum vacuum adsorption force by the proposed SEM method.
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