METHOD FOR MEASURING THE ACTIVE KOH CONCENTRATION IN A KOH ETCHING PROCESS

摘要

The invention relates to a method for in-line measuring the active KOH concentration in a KOH etching process in which process silicon hydroxide is produced by a reduction reaction according to the formula: 2K+ (aq.) + 2OH- (aq.) + 2H2O + Si - 2K+ (aq.) + H2SiO42- (aq.) + 2H2 (g). The total concentration of KOH bath is measured by using a refractometer and the measurement result is corrected by the estimated K2H2SiO4 concentration.