| 摘要 |
PROBLEM TO BE SOLVED: To easily control the amount of etching of a film to be etched by controlling the chemical concentration by accurately finding a mixing ratio of cleaning chemical to refill a required amount of chemical. SOLUTION: In the replacement of chemicals, the amounts of supply of chemicals 21, 22, 23 to be supplied to a chemical tank 1 are measured by chemical flow meters 31, 32, 33, respectively. With the measured flow rate, a supply time is calculated in an operation part 7 and the total input of each chemical is calculated from the integral of the supply flow rate and the supply time. The mixing ratio is found from the total input of each chemical and the chemical concentration is calculated. At this point, if the calculated concentration is different from the set concentration, an amount of refill of each chemical is calculated in the operation part 7 so that a desired chemical concentration is obtained and the amount of refill is adjusted by varying the supply time. Only the chemical to be refilled is supplied to the chemical tank 1 by opening a mixing valve 4 for the supply time calculated in the operation part 7 and thus the chemical concentration is adjusted. COPYRIGHT: (C)2009,JPO&INPIT
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