DEVICE FOR CONTROLLING CONCN. OF ETCHING SOLN

PROBLEM TO BE SOLVED: To provide a system for controlling concn. of an etching soln. which can control concn. of the etching soln. and can control an etching shape and an etching rate. SOLUTION: A wet etching device 11 which executes fine working an aluminium or a metallic thin film consisting essentially of aluminium is provided with an ion chromatograph 12 which can measure the concn. of the etching soln., a controller 13 which can calculate quantity of the etching soln. to be added based on the measured result and an etching soln. adding device 14 supplying the prescribed etching soln. to the etching device 11. Thereby concn. of the etching soln. of a blending system of phosphoric acid, nitric acid, acetic acid and water is controlled within a set concn. range. Further, composition of the etching soln. in a spray type etching device can be stabilized by adding necessary amount of nitric acid and acetic acid corresponding to composition change thereof and the etching shape and the etching rate are controlled within a prescribed range and can be stabilized by controlling the concn. of the etching soln.