Multilayer extreme ultraviolet mirrors with enhanced reflectivity
US6449086B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Jun 28, 2000 |
| Grant date | Sep 10, 2002 |
| Priority date | — |
| Expiry date | Jun 28, 2020 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/24355
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The reflectivity of multilayered EUV mirrors tuned for 11-16 nm, for which the two-component Mo/Be and Mo/Si multilayered systems are commonly used, is enhanced by incorporating additional elements and their compounds mainly from period 5 of the periodic table. In addition, the reflectivity performance of the multilayer stacks is further enhanced by a numerical global optimization procedure by which the layer thicknesses are varied for optimum performance in, contradistinction to the constant layer thickness—i.e. constant partition ration—multilayer stacks commonly designed and fabricated hitherto. By incorporating additional materials with differing complex refractive indices in various regions of the stack, or by wholly replacing one of the components (typically Mo), peak reflectivity enhancements of up to 5% for a single reflector are achieved, compared to a standard unoptimized stack. The additional materials used are: Rb, RbCl, Sr, Y, Zr, Ru, Rh, Tc, Pd, Nb and Be. Protective capping layers of B, Ru, Rh, C, Si3N4, SiC, are disclosed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.