Winston Larson American Vacuum Society Conference

1. Determining Physical and Chemical Constants of Sputtered Uranium and Thorium as Thin Film Reflectors Within the Extreme Ultraviolet (EUV) Winston Larson American Vacuum Society Conference

2. Overview • Practical applications and importance of research • Experiments • Results • Conclusions • Discussion of Conclusions

3. Why EUV? • EUV Lithography • 10 Ghz by 2007 • 32 nm nodes • EUV Astronomy • Earth’s Magnetosphere • Background Imaging

4. EUV Lithography Absorber Pattern Reflective Mask λ = 4 nm Reduction optics Wafer to record 32 nm or smaller features

5. Uranium and Thorium • Uranium and Thorium are very dense and are highly reflective in the EUV range. • Uranium oxide, uranium nitride, thorium metal, and thorium dioxide were studied.

6. Structure • The structure will affect the reflectance: • Compound • Relative Density • Lattice Structure • Roughness

7. TEM and AFM Experimentation • Samples made on TEM grids and silicon wafers using RF Magnetron sputtering • The TEM was used to obtain diffraction patterns. • Analyzed for compound, relative density, and lattice structure. • The AFM was used to obtain roughness data. • RMS roughness used to find change in reflectance. • Power Spectral Density

9. TEM Analysis • Bragg’s Law used to analyze diffraction patterns and find lattice parameters. • Lattice Parameters used to find compound, lattice structure, and relative density. • Lattice Parameters found for thorium, uranium nitride and uranium oxide.

10. Uranium nitride diffraction pattern taken at 160 keV and 130 cm.

11. TEM Conclusions • Thorium lattice parameters were around 5.08 Å, representing thorium metal. • Uranium oxide lattice parameters were around 5.47 Å, representing uranium dioxide. • Uranium nitride lattice parameters were around 4.98 Å, representing uranium mononitride. • All compounds had a face-centered cubic structure.

12. 1 Rough Surface 2 Smooth Surface

13. AFM Roughness Analysis • Debye-Waller method used, which overestimates effect on reflectance. • Nevot-Croce method also used, which underestimates effect on reflectance. • Results from both methods averaged to find a good estimate of change in reflectance.

14. The surface of uranium oxide at 100 nm by 100 nm.

15. High Frequency Roughness Detector

16. Low Frequency Roughness Detector

17. Power Spectral Density • Shows high frequency roughness and low frequency roughness. • All samples were mostly high frequency roughness with little low frequency roughness.

18. AFM Conclusions • Change in thorium reflectance was about 20%. • Change in uranium oxide reflectance was about 40%. • Change in uranium nitride relfectance was about 10%.

19. Combined Conclusions • Thorium • Second highest density • Second lowest roughness • Second best reflectance • Uranium Dioxide • Lowest density • Highest roughness • Worst reflector • Uranium Mononitride • Highest Density • Lowest roughness • Best reflector

23. Why This is Important • Again, the many practical applications. • Structure greatly affects the reflectance of thorium and uranium. • Good basis for more sophisticated research in the future. • A good estimate of the reflectance can be made when a sample is sputtered.

24. Review • Practical applications and importance of research • Experiments • Results • Conclusions • Practical Applications

25. Acknowledgements • Thanks to • Dr. Allred • Dr. Turley • Niki Farnsworth • Richard Sandberg • Jed Johnson • Luke Bissell • Mom and Dad • Everyone else who so kindly helped me • Santa, because I believe

26. The End! • Any questions, comments, cares, concerns, feelings, other appropriate emotions, or otherwise important things that need to be expressed to our happy group while we are here together in such a pleasant setting?