Point-of-use recycling of wafer cleaning substances
AssigneeFSI International, Inc.
InventorDonald C. Grant
Life of this patent
Estimating the term…
Abstract
A method of recycling and purifying cleaning chemicals used in the production of semiconductor circuits and containing hydrofluoric acid and or hydrochloric acid. Recycling of such chemicals is accomplished using separation and reconstitution steps Hydrofluoric acid and hydrochloric acid cannot be distilled directly from a chemical solution as they form azeotropes with water. A low vapor pressure substance such as sulfuric acid or phosphoric acid is used to break the azeotrope while increasing the purity of the recovered chemicals and decreasing disposal problems. The method is useable at the point of use of the chemicals.
Claims13
A closed loop process involving use, purification, recovery and reuse of an acid in a wafer surface conditioning process, comprising:
- (a) conditioning the surface of a wafer with an acid selected from the group consisting of hydrochloric acid, hydrofluoric acid, hydrobromic acid, nitric acid, whereby the acid is contaminated with matter removed from the surface of the wafer;
- (b) adding a low vapor pressure liquid adjuvant to an azeotrope forming aqueous solution of the contaminated acid at a volumetric ratio of adjuvant to contaminated aqueous solution of about 0.4:1 to 2:1 to form a reaction mixture whereby the azeotrope forming attribute of the contaminated solution is broken;
- (c) separating the reaction mixture to form a primary acid-depleted adjuvant-containing contaminated aqueous liquid phase and a primary acid-enriched, adjuvant-depleted, substantially contaminant free, water vapor containing gaseous phase;
- (d) separating the contaminated primary liquid phase into a secondary adjuvant-depleted, contaminated aqueous liquid phase and a secondary adjuvant-enriched, substantially contaminant free, water vapor containing gaseous phase;
- (e) reconstituting the primary gaseous phase to form a purified acid with a purity effective for use in a wafer surface conditioning process;
- and
- (f) conditioning the surface of a wafer with the purified acid.
Dependencies are inferred from the claim text.