| 摘要 |
PURPOSE: A measuring method of contained impurity in graphite is provided to prevent pollution of a wafer by quantitative analysis. CONSTITUTION: Graphite for semiconductor manufacturing is ground to get a sample of graphite powder. 70% of nitric acid solution and 98% of sulphuric acid are mixed. The mixed solution is barreled in a melting pot; also, the graphite sample powder is also put in the melting pot. The melting pot is loaded in an electric furnace and heated for 36 hours at 230 deg.C. The remaining solution in the melting pot is heated by a hot plate to evaporate nitric acid and sulphuric acid. The dried sample is pit in a mixed solution of nitric acid, sulphuric acid, and deionized water to gather impurity. The amount of impurity is measured using analysis equipment such as AAS(Atomic Absorption Spectrometer) or ICP(Inductively Coupled Plasma Spectrometer).
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