Patent ID: 7323063

Claim:
A treatment solution supply apparatus for supplying a treatment solution to a substrate, comprising: a tank for storing the treatment solution; a first pipe for connecting said tank to a treatment solution supply section for supplying the treatment solution to the substrate; a treatment solution supply pipe for supplying the treatment solution with a predetermined concentration into said tank; a diluting fluid supply pipe for supplying a diluting fluid into said tank; a solution volume sensor for measuring a solution volume in said tank; a drainpipe for draining out the treatment solution from said tank; a drainpipe flowmeter provided along said drainpipe and configured to measure a drain volume of the treatment solution flowing through said drainpipe; a concentration sensor for directly measuring a concentration of an existing treatment solution in said tank; an arithmetic unit for calculating a drain volume of the existing treatment solution to be drained out from said drainpipe and calculating a supply volume of the treatment solution with the predetermined concentration to be supplied from said treatment solution supply pipe or a supply volume of the diluting fluid to be supplied from said diluting fluid supply pipe respectively, in order to change the existing treatment solution in the tank to be in an intended volume and to have an intended concentration; a supply control unit for controlling the supply volume from said treatment solution supply pipe and said diluting fluid supply pipe based on a resultant value of the calculation; and a drain control unit for controlling the drain volume as measured by the drainpipe flowmeter of the existing treatment solution from said drainpipe based on a resultant value of the calculation, wherein the drainpipe is configured to carry substantially all of the solution flowing through the drainpipe outside of the apparatus.