Analysis of silicon concentration in phosphoric acid etchant solutions
US8008087B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 25, 2010 |
| Grant date | Aug 30, 2011 |
| Priority date | — |
| Expiry date | Mar 25, 2030 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T436/193333
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Low concentrations of silicon in an etchant solution are analyzed by adding a predetermined concentration of fluoride ions to a test solution comprising a predetermined volume of the etchant solution, and measuring the concentration of fluoride ions in the test solution. Reaction with silicon ions in the test solution reduces the concentration of fluoride ions, which are present in stoichiometric excess, so that the silicon concentration of the etchant solution can be calculated from the difference between the predetermined and measured concentrations of fluoride ions in the test solution. The method is especially suited for analysis of silicon nitride etchants comprising a high concentration of phosphoric acid.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.