Patent ID: 6350425
Filing Date: 2002-02-26
Classification: C01B,C01C,G05D,H01L

Abstract:
A method of preparing buffered-hydrofluoric acid or ammonium fluoride, suitable for use in fabricating semiconductor devices, comprising contacting high-purity water and hydrofluoric acid, thereby forming a diluted hydrofluoric acid and bubbling purified ammonia vapor into the diluted hydrofluoric acid, wherein the concentration of the buffered-hydrofluoric acid or ammonium fluoride is controlled by a step for detecting an endpoint of the bubbling, wherein the step of contacting the high-purity water and the hydrofluoric acid and the step of bubbling purified ammonia vapor into the diluted hydrofluoric acid occur in the same vessel, and wherein the hydrofluoric acid is prepared by a process comprising the steps of:removing a flow of hydrogen fluoride vapor from a source of hydrogen fluoride; contacting said hydrogen fluoride vapor with a recirculating volume of high-purity water containing a high concentration of hydrogen fluoride in a hydrogen fluoride ionic purifier unit, wherein said hydrogen fluoride ionic purifier unit passes purified hydrogen fluoride gas; and combining the hydrogen fluoride gas with acidic deionized water to produce the hydrofluoric acid.