Abrasive properties of nano silica particles prepared by a sol–gel method for polishing silicon wafers |
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Authors: | Kazuaki Yoshida |
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Institution: | (1) School of Engineering, Nippon Bunri University, 1727 Ichigi, Oita-shi, Oita 870-0397, Japan |
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Abstract: | Abrasive properties of cocoon shaped silica particles fabricated by a sol–gel method have been studied. Since silicon wafers
are polished with slurry by the mechanism of Chemical Mechanical Polishing, polishing rates may depend on various chemical
and mechanical factors, such as particle concentration in slurry, slurry pH and kinds of basic compounds for controlling the
slurry pH.
The silicon wafer was polished by slurry continuously fed on a pad, and the polishing rate was estimated as a weight loss
of the wafer. For studying the effects of the various factors on the rate, the slurries were prepared by adding the silica
particles, basic compounds or salts, and the polishing rates of the slurry were measured.
The effects of the various factors were made clear as follows: For the effect of particle concentration, the rates increased
with increasing of the concentrations up to 1.0 wt.%. And for the effect of the slurry pH, slurries added basic compounds,
such as KOH, NaOH, ammonia, were tested, and it was found that increasing of the slurry pH brought increases of the polishing
rates. KOH-containing slurry of pH 13.2 had the fastest rate, 3.6 times as fast as the standard slurry with pH 9.4. For the
effect of the adding of salts, it was indicated that the salts, such as KCl, NaCl, NH4Cl, NaNO3 and K2SO4 increased the polishing rates, and that KCl-containing slurry of 0.36 mol/l had the highest polishing rate, 3.4 times as
fast as that of the standard slurry containing no salts. |
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Keywords: | Silica particle Polishing Abrasive Silicon wafer Slurry |
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