Patent ID: 6921193

Claim:
A chemical concentration control device for a concentration feedback control system of a semiconductor processing apparatus, said chemical concentration control device comprising: a concentration measuring unit for measuring concentrations of chemicals; a drift observation unit for observing a drift amount of the concentrations after an overhead time of the concentration feedback control system has elapsed; a replenishment quantity calculating unit for calculating replenishment quantities of the chemicals; a fixed-quantity replenishment processing unit for processing a replenishment quantity of each of the chemicals so that a summation of the replenishment quantities of respective chemicals calculated by the replenishment quantity calculating unit becomes equal to a predetermined reference replenishment quantity; a concentration estimating unit for estimating concentrations to be achieved after the chemicals have been replenished by the replenishment quantities calculated by the fixed-quantity replenishment processing unit; and a replenishment control unit for controlling replenishment of the chemicals based on the replenishment quantities calculated by the fixed-quantity replenishment processing unit.