Patent ID: 7713478

Claim:
Equipment for measuring a silicon concentration in a phosphoric acid solution under use as an etching solution during operation of a semiconductor substrate processing system, said measuring equipment comprising: a reaction tank containing phosphoric acid solution comprising silicon compounds that is drawn from the processing system into the reaction tank; a concentration-measuring tank containing deionized water, said concentration-measuring tank being separate from the reaction tank; and a gas feed line connected between the reaction tank and the concentration-measuring tank, wherein the reaction tank comprises: a phosphoric acid solution feed line connected between the reaction tank and a phosphoric acid solution recirculation line of the processing system, to feed the phosphoric acid solution comprising silicon compounds that is drawn from the processing system into the reaction tank; a hydrofluoric acid feed line connected to the reaction tank, to feed hydrofluoric acid into the reaction tank; a means for evaporating, into silicon fluoride gas, silicon fluoride compounds formed by reaction between the phosphoric acid solution and the hydrofluoric acid inside the reaction tank; and a means for feeding an inert gas from a lower part of the reaction tank into the phosphoric acid solution in the reaction tank, wherein the gas feed line feeds the silicon fluoride gas from the reaction tank into the concentration-measuring tank, and wherein the concentration-measuring tank comprises: a deionized water feed line connected to the concentration-measuring tank, to feed the deionized water into the concentration-measuring tank; a means for bubbling connected to the gas feed line and arranged inside the concentration-measuring tank, that causes the silicon fluoride gas from the gas feed line to bubble into the deionized water in the concentration-measuring tank, to hydrolyze the silicon fluoride gas in the deionized water; and a means for determining a change rate of silicon concentration in the deionized water in the concentration-measuring tank subsequent to said bubbling.