Preparation of 157nm transmitting barium fluoride crystals with permeable graphite
US6855203B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 28, 2002 |
| Grant date | Feb 15, 2005 |
| Priority date | — |
| Expiry date | May 8, 2022 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC30B29/12
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
The object of the present invention is a process of preparing an optical fluoride crystal containing barium fluoride, which comprises: loading a crucible with a barium fluoride starting material crystal feedstock which contains at least one oxide as impurity, and an effective and non-excess amount of at least one fluorinating agent which is solid at ambient temperature, melting said mixture within said crucible, growing the crystal, by controlled cooling of the molten mixture, controlled cooling of said crystal to ambient temperature, recovering said crystal; and which is characterized in that the oxide(s) resulting from the reaction between said fluorinating agent(s) and said oxide(s), the impurity or impurities, can be discharged from said crucible, in view of the intrinsic permeability of the material constituting it. Said process is particularly adapted for preparing 157 nm transmitting lithography excimer laser optical fluoride crystals in graphite crucibles.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.