Method and apparatus for the continuous on-site chemical reprocessing of ultrapure liquids used in semiconductor wafer cleaning
US4855023A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 19, 1988 |
| Grant date | Aug 8, 1989 |
| Priority date | — |
| Expiry date | Apr 19, 2008 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S134/902
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
An improved wafer cleaning process wherein a novel oxidant solution comprising ultrapure sulfuric acid, peroxydisulfuric acid, and ultrapure water used in a semiconductor wafer cleaning process is continuously withdrawn after use. The withdrawn oxidant is reprocessed continuously by contacting with alumina to remove fluoride ions. Water is continuously separated or stripped from the oxidant solution by heating the solution and bubbling an inert gas therethrough. The separated oxidant is continuously distilled and condensed to form a purified stream of sulfuric acid. The major portion of this stream is continuously returned to the wafer cleaning process. The remaining minor portion is continuously cooled, subjected to analysis for purity, and diluted with ultrapure water prior to electrochemical treatment in the anode compartment of an electrochemical cell. This converts at least a portion of the dilute sulfuric acid to peroxydisulfuric acid. The resulting solution is continuously returned to the wafer cleaning process to be mixed with the major portion of the purified sulfuric acid.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.