Patent ID: 7557041

Claim:
A method of producing a semiconductor device comprising: providing a first tank and a second tank for preparing a slurry to be used alternately from the tanks; preparing a first batch of the slurry in the first tank; polishing wafers with the slurry of the first batch in a CMP processing unit; delaying starting preparation of a second batch of the slurry in the second tank until a signal is received from the first tank indicating liquid level of the slurry in the first tank has dropped to a first preparation start value during a period of time when the slurry in the first tank is used for polishing the wafers, and then preparing a second batch of the slurry in the second tank; and beginning polishing additional wafers with the slurry of the second batch in the CMP processing unit when signal is received from the first tank indicating the liquid level of the slurry in the first tank has dropped to a second low level value.