NASA 1996 SBIR Phase I

PROPOSAL NUMBER : 96-1 13.08-0204

PROJECT TITLE : Low Cost, High Purity SiC for High Reflectivity Extreme Ultraviolet Mirror Substrates


The next generation of extreme ultraviolet (EUV) space-based remote sensing instru-mentation requires mirror substrates which are thermally stable, ultralightweight, & low-cost with excellent surface finishes & high EUV reflectivities. These requirements become more stressing as future systems will grow in size (~1 meter apertures for the KRONOS instrument on the SMEX platform). Because of its excellent bulk material properties (superior thermal stability & specific stiffness) SiC has been evaluated for these applications. Traditional Reaction Bonded (RBO) SiC has excellent near-net-shape fabrication processes & good bulk material properties, however it has poor EUV reflectivity due to its limited surface finish capabilities. Chemical Vapor Deposition (CVD) SiC has excellent surface finish capabilities & superior EUV reflectivity, but the material is very expensive. SSG proposes the application of a newly developed, high purity form of SiC for development of high reflectivity, low cost EUV mirror substrates. The material proposed maintains the low-cost features associated with RBO SiC while maintaining the key technical properties of the CVD SiC. The excellent surface finishes obtained with the material, due to its high purity & homogeneity, suggest that it will provide a superior EUV reflectivity which is more in line with the CVD form of the material. The cost differential possible with this new SiC form is significant (>10x less expensive than CVD SiC) & in this way can greatly impact the cost of the next generation of EUV space astronomy instrumentation being developed by NASA. NASA Goddard has evaluated the material for EUV reflectivity & obtained promising preliminary results. The objective of the proposed Phase I SBIR will be to confirm these results with more rigorous tests, & to further refine the high purity form of SiC specifically for EUV applications. The Optics Branch at NASA Goddard is very interested in this material & has agreed to support SSG during Phase I, providing inputs with respect to requirements & performing EUV reflectivity measurements. A successful Phase I effort will quantify the cost & performance improvements possible with the high purity SiC material & lay the ground work for a system level demonstration of an ultralightweight, thermally stable, high reflectivity SiC optical system in Phase II.
The low cost, high EUV reflectivity and excellent thermal stability of the proposed SiC material will make it very attractive for a number of commercial applications including UV and x-ray lithography where very smooth, thermally stable surfaces are required. The low cost nature of the material will also make it suitable for next generation space and air-based remote sensing systems.
SSG, Inc.
150 Bear Hill Road
Waltham, MA 02154