Transmission Grating Spectrometer for EUV Lithography Nathan Gray Advisors: Alexander Shevelko, Larry Knight, and Scott Bergeson Student Group Members: Matthew Harrison, Jeff Kemp, Bryce Allred, Jershon Lopez
Extreme Ultraviolet (EUV) Å Image modified from: NASAexplores Models of the Electromagnetic Spectrum student sheet. lot.astro.utoronto.ca/spectrum.htmllot.astro.utoronto.ca/spectrum.html
Extreme Ultraviolet (EUV) Å Image modified from: NASAexplores Models of the Electromagnetic Spectrum student sheet. lot.astro.utoronto.ca/spectrum.htmllot.astro.utoronto.ca/spectrum.html Absorbed by Everything: Air
Extreme Ultraviolet (EUV) Å Image modified from: NASAexplores Models of the Electromagnetic Spectrum student sheet. lot.astro.utoronto.ca/spectrum.htmllot.astro.utoronto.ca/spectrum.html Absorbed by Everything: Air Glass
Extreme Ultraviolet (EUV) Å Image modified from: NASAexplores Models of the Electromagnetic Spectrum student sheet. lot.astro.utoronto.ca/spectrum.htmllot.astro.utoronto.ca/spectrum.html Absorbed by Everything: Air Glass Plastic
Extreme Ultraviolet (EUV) Å Image modified from: NASAexplores Models of the Electromagnetic Spectrum student sheet. lot.astro.utoronto.ca/spectrum.htmllot.astro.utoronto.ca/spectrum.html Absorbed by Everything: Air Glass Plastic Ponies
Extreme Ultraviolet (EUV) Absorbed by Everything: Air Glass Plastic Must operate under vacuum (our chamber is at mtorr) Must use mirrors in place of conventional optics. This makes spectroscopy in the EUV range complicated.
EUV range transmission gratings:
Recent transmission grating development allows for EUV range gratings 200 nm period (5000 lines/mm)
EUV range transmission gratings: Recent transmission grating development allows for EUV range gratings 200 nm period (5000 lines/mm) Transmission grating spectrometers are superior to reflection grating spectrometers
Possible Configurations Entrance Slit Grating Detector Simple Transmission Grating Spectrometer
Possible Configurations Single Mirror Geometry Single Mirror Geometry Entrance Slit Grating Detector Spherical Mirror High spectral resolution and luminosity Mirror collects large solid angle
Our Configurations Double Mirror Geometry Double Mirror Geometry Grating Entrance Slit Flat Mirror Detector Spherical Mirror Designed by Dr. Alexander Shevelko
Knight/Shevelko Group Spectrometer Configuration
Electron Temperature Study Tungsten
Efficiency Calculation Major advantage of transmission grating over reflection grating Must take transmission through wires into account (phase shift) Materials: Au 25 nm Si4N3 200 nm Radiation
Formulae
Efficiency Calculation Fujikawa et al. Method Schopper et al. Method H. W. Schopper et al., Appl. Opt. 16, 1088 (1977). C. Fujikawa et al., Rev. Sci. Instrum. 69, 2849 (1998).
Absolute Calibration grating efficiency X spherical mirror reflectivity X flat mirror reflectivity = total spectrometer efficiency = total spectrometer efficiency
Absolute Calibration grating efficiency X spherical mirror reflectivity X flat mirror reflectivity = total spectrometer efficiency = total spectrometer efficiency total spectrometer efficiency X detector calibration = absolute calibration
Absolute Calibration grating efficiency X spherical mirror reflectivity X flat mirror reflectivity = total spectrometer efficiency = total spectrometer efficiency total spectrometer efficiency X detector calibration = absolute calibration absolute calibration = Intensity scaled to units of actual photon flux, instead of just relative intensity.
Absolute Calibration grating efficiency X spherical mirror reflectivity X flat mirror reflectivity = total spectrometer efficiency = total spectrometer efficiency total spectrometer efficiency X detector calibration = absolute calibration absolute calibration = Intensity scaled to units of actual photon flux, instead of just relative intensity. Detector calibration: completed at Lebedev Physical Institute by Oleg Yakushev
EUV Lithography International Technology Roadmap for Semiconductors printable patterns with 32 nm between features are required by the semiconductor industry by 2009
EUV Lithography Main limitation is wavelength of light source Higher Resolution requires a source with smaller wavelength
V. Bakshi, EUV Sources for Lithography, SPIE Press Book, V. Bakshi, EUV Sources for Lithography, SPIE Press Book, Typical EUV wafer scanner
EUV Lithography Typical EUV Lithography apparatus: 11 mirror multilayer Mo/Sn multilayer mirrors with reflections around 66% each. The overall transmission in the EUV scanner is less than 1%, The mirrors reflect a bandwidth of 2% around a central wavelength of 135 °A.
EUV Lithography Source candidates: Lithium and Tin plasmas
EUV Lithography Mirror heating Mirror heating Unwanted radiation Unwanted radiation Target purity Target purity Plasma parameters (electron temperatures, absolute outputs, etc.) Plasma parameters (electron temperatures, absolute outputs, etc.)
Current WRS Planned WRS with multiple gratings
Acknowledgements Dr. Shevelko Dr. Shevelko Dr. Knight Dr. Knight Matt Harrison and the other members of my group Matt Harrison and the other members of my group The chemists (especially Dr. Asplund) The chemists (especially Dr. Asplund)