Simultaneous Monitoring Method for Chemical Constituents in Aluminum Etchant

A simultaneous monitoring method to determine the chemical constituents in an aluminum etchant was developed using capillary electrophoresis, as a substitute for the wet titration method that requires long analysis time and tedious work. Anions of acetate, nitrate, and ammonium ions were separated from the phosphate matrix within 20 min when a sample of less than a nanoliter was injected. Each identified peak was integrated to determine the target ions quantitatively with an indirect detection mode. From the calibration curve, the detection limits of each ingredient were obtained in the range of 0.98 to 3.57 g/g with a relative standard deviation (n=4) of less than ±6.05% from the peak area measurement. A lab-built system based on the developed analytical technique was demonstrated to monitor the change of chemical constituents in a buffer etchant typically used in the liquid crystal display manufacturing process. The adaptation of this monitoring system to the production line can lengthen the lifetime of the process chemicals and provide eco-friend recycling for lower chemical consumption.