PRECISION FINISHING OF MONO-CRYSTAL SILICON BALLS FOR SPHERICAL SEMI-CONDUCTORS

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In this study, we focused our attention to a polishing technology for mono-crystal Silicon balls, which is very small (under 1 mm in diameter) and are expected to be applied to ball semi-conductors. The spherical surface of the ball-shaped semi-conductors should be finished in perfect smooth surface for making IC circuits on it, similarly for a Silicon wafer, by means of the photo-rithography method. The ball-shaped semi-conductors are excellent in production efficiency because precision silicon balls are easily mass-producedIn order to establish this new technology in the silicon semi-conductor's industry, the development of a new precision polishing machine for the small Silicon balls is demanded eagerlyAt the beginning of this study in 2001, we designed and produced a polishing device on trial and investigated its polishing abilities experimentally. At the same time, we tried to produce polishing slurry by the sol-gel method and got some successful results. However, these were not sufficient for actual applicationsThis year, we adopted a new idea, namely that centrifugal force should be used for polishing small Silicon balls and then built a polishing device. The polishing principle is suitable for high-speed, automated and mass-productive polishing of silicon balls. Therefore, we can expect drastic effects by the newly designed polishing deviceBy using the new polishing machine, the following results were obtained(1) The polishing machine has an excellent polishing ability for small Silicon balls(2) Polishing accuracy of roundness, achieved by the polishing machine, is better than conventional ones. That is, we can easily get the roundness under 0.0001 mm(3) This polishing method is suitable for automatic polishing process of Silicon balls