High efficiency multilayer blazed gratings for EUV and soft X-rays: Recent developments
Multilayer coated blazed gratings with high groove density are the best candidates for use in high resolution EUV and soft x-ray spectroscopy. Theoretical analysis shows that such a grating can be potentially optimized for high dispersion and spectral resolution in a desired high diffraction order without significant loss of diffraction efficiency. In order to realize this potential, the grating fabrication process should provide a perfect triangular groove profile and an extremely smooth surface of the blazed facets. Here we report on recent progress achieved at the Advanced Light Source (ALS) in fabrication of high quality multilayer coated blazed gratings. The blazed gratings were fabricated using scanning beam interference lithography followed by wet anisotropic etching of silicon. A 200 nm period grating coated with a Mo/Si multilayer composed with 30 bi-layers demonstrated an absolute efficiency of 37.6percent in the 3rd diffraction order at 13.6 nm wavelength. The groove profile of the grating was thoroughly characterized with atomic force microscopy before and after the multilayer deposition. The obtained metrology data were used for simulation of the grating efficiency with the vector electromagnetic PCGrate-6.1 code. The simulations showed that smoothing of the grating profile during the multilayer deposition is the main reason for efficiency losses compared to the theoretical maximum. Investigation of the grating with cross-sectional transmission electron microscopy revealed a complex evolution of the groove profile in the course of the multilayer deposition. Impact of the shadowing and smoothing processes on growth of the multilayer on the surface of the sawtooth substrate is discussed.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- Advanced Light Source Division
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 1045927
- Report Number(s):
- LBNL-4992E; TRN: US1203695
- Resource Relation:
- Conference: SPIE 2010 Optics and Photonics
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
47 OTHER INSTRUMENTATION
ADVANCED LIGHT SOURCE
ATOMIC FORCE MICROSCOPY
DEPOSITION
DIFFRACTION
EFFICIENCY
ETCHING
FABRICATION
OPTICS
RESOLUTION
SILICON
SIMULATION
SUBSTRATES
TRANSMISSION ELECTRON MICROSCOPY
VECTORS
X-RAY SPECTROSCOPY
diffraction grating
diffraction efficiency
blazed grating
multilayer coating
scanning beam interference lithography
wet anisotropic etch
EUV
soft x-rays
TEM