Ultrapure colloidal silica for use in chemical mechanical polishing applications
US8779011B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 24, 2012 |
| Grant date | Jul 15, 2014 |
| Priority date | — |
| Expiry date | Feb 24, 2032 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L21/3212
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
Abstract
A method for producing and using an ultrapure colloidal silica dispersion is disclosed. The ultrapure colloidal silica dispersion has less than 200 ppb of each trace metal impurity disposed therein, excluding potassium and sodium, and less than 2 ppm residual alcohol. The method comprises dissolving a fumed silica in an aqueous solvent comprising an alkali metal hydroxide to produce an alkaline silicate solution, removing the alkali metal via ion exchange to generate a silicic acid solution, adjusting temperature, concentration and pH of said silicic acid solution to values sufficient to initiate nucleation and particle growth, and cooling the silicic acid solution at a rate sufficient to produce the colloidal silica dispersion.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.