Manufacturing method for calcium fluoride and calcium fluoride for photolithography
US6332922A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 25, 1999 |
| Grant date | Dec 25, 2001 |
| Priority date | — |
| Expiry date | Feb 25, 2019 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S117/906
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A manufacturing method for a single crystal of calcium fluoride by which it is possible to obtain a single crystal of calcium fluoride with adequately small double refraction, which can be used in optical systems for photolithography, and in particular, a single crystal of calcium fluoride with a large diameter (.o slashed. 200 mm or larger) having superior optical properties, which can be used for photolithography with a wavelength of 250 nm or less. A manufacturing method for a single crystal of calcium fluoride, having its optical properties improved through an annealing process in which a single crystal of calcium fluoride is contained in a sealable container, and said container is sealed and vacuumed, followed by, a process of heating with a heater arranged external to said container so that the temperature inside said container is raised to a first temperature, which is lower than the melting point of said single crystal of calcium fluoride, a process by which the temperature inside said container is maintained at said first temperature for a designated period of time, and a process by which the temperature inside said container is lowered to room temperature, wherein, the ma…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.