Abstract: The aluminum etchant is a mixture composed of nitric acid, acetic acid, and phosphoric acid, and concentration changes of each acid in etchant will affect the etching. In mass production, the equipment replenishes nitric acid and acetic acid to keep their concentrations stable, while the phosphoric acid concentration will gradually decrease without replenishment. In this paper, the influence of phosphoric acid concentration on the etching degree was studied when the monoacid supply is turned on and off. Then combined with TRIZ, the phosphoric acid concentration decline was analyzed. At last, the TRIZ solution was output to avoid the decrease in phosphoric acid concentration. The results show that nitric acid and acetic acid are gradually consumed, and the etching ability is reduced when the monoacid supply is turned off. However, when the monoacid supply is turned on, the concentration of nitric acid and acetic acid is stable, and the concentration of phosphoric acid gradually decreases, and the etching ability is also reduced. The supplied nitric acid and acetic acid contain water, which dilutes the phosphoric acid, causing the concentration of phosphoric acid to decrease. In addition, decreased etching ability will lead to metal residues, which in turn will cause yield damage. Combined with the TRIZ solution, measures such as increasing the exhaust of the etching chamber, decreasing flow rate of air curtain at the etching outlet, and adjusting the product type according to the use time of the etchant, can avoid the influence of the drop in the concentration of phosphoric acid. This research provides a reference for product yield improvement.

Key words: Aluminum etchant, Phosphoric acid concentration, Etch ability, TRIZ