Patent Number: 6,253,781

Title: Process for controlling the level of an ammonium fluoride-containing acid solution in an acid vessel

Abstract: The present invention provides a process for controlling the level of an ammonium fluoride-containing acid solution in an acid vessel. First, a tube provided with at least one hole in the sidewall is used as a high level sensing tube for the acid solution in the acid vessel. Then, an inert gas is blown into the high level sensing tube. The pressure of the inert gas is measured such that the acid solution is charged when the pressure is a first value and the acid solution is drained when the pressure is a second value larger than the first value. By means of the process of the present invention, when the bottom of the high level sensing tube is jammed with ammonium fluoride crystals and the acid solution level has not reached a level submerging the at least one hole, the inert gas can flow out via the at least one hole and the pressure measured is the first value. Thus, the period of time before the dummy wet station is shut down due to the accumulation of ammonium fluoride crystals on the high level sensing tube can be prolonged. Consequently, the usage time of the acid solution can be greatly lengthened, the frequency of changing acid can be decreased, and the frequency of the preventive maintenance of the dummy wet station can be decreased, thus increasing production efficiency.

Inventors: Lee; Ching-Lun (Taipei, TW)

Assignee: Winbond Electronics Corporation

International Classification: G01F 23/14 (20060101); G01F 23/16 (20060101); G01F 023/14 ()

Expiration Date: 07/03/2018