Multilayer Interference Coating, Scattering, Diffraction, Reflectivity mλ = 2d sin θ (W/C, T. Nguyen) Normal incidence reflectivity 1..5 1 nm MgF 2 /Al Si C Pt, Au 1 ev 1 ev Wavelength 1 nm 1 nm.1 nm Multilayer mirrors ( ) Photon energy Natural crystals 1 KeV 1 KeV (D. Windt, D. Stearns, J. Kortright) Ch4_F_Feb27.ai
Scattering by Density Variations Within a Multilayer Coating Mo/Si (T. Nguyen, CXRO/LBNL) Ch4_F1_Feb27.ai
Scattering of Radiation by a Sinusoidal Density Distribution (Atoms or Electrons) A n a (z) B A B A d B k i A θ 2θ k d = 2π d z o k i z k s k s Ch4_F2VG.ai
Scattering from Density Variations In the long wavelength limit (λ >> a ) (4.1) (4.2) (4.3) (4.4a) (4.4b) (4.5a) (4.5b) or (4.6a) (4.6b) k i 2θ k d = 2π d z o k s Ch4_Eqs1_6VG.ai
Multilayer Mirrors Satisfy the Bragg Condition d Mo Si Mo Si Mo Si Mo Si mλ = 2d sinθ n e θ λ For normal incidence, θ = π/2, first order (m = 1) reflection λ = 2d d = λ/2 if the two layers are approximately equal t λ/4 a quarter-wave plate coating. Ch4_MltlyrMirBragg1.ai
Multilayer Mirrors Satisfy the Bragg Condition d Mo Si Mo Si Mo Si Mo Si 4δd mλ = 2d sinθ (1 2 ) m 2 λ 2 n e θ λ For normal incidence, θ = π/2, first order (m = 1) reflection λ = 2d d = λ/2 if the two layers are approximately equal t λ/4 a quarter-wave plate coating. Ch4_MltlyrMirBragg2.ai
High Reflectivity Multilayer Coatings Require: Refractive index contrast at the interfaces Minimal absorption in the low-z material Thin high-z layer where possible Γ ; Δτ H /(Δτ H + Δτ L ) Interfaces which are chemically stable with time Minimal interdiffusion at the interfaces Minimal interfacial roughness (no crystallite formation within the layers, no shadowing in the coating process, surface mobility) Thermal stability during illumination Chemically stable vacuum interface (e.g., Si 2 or capping layer) Uniform coating thickness Univ. California Berkeley Multilayer Interference Coating, Scattering, Diffraction, Reflectivity, EE29F, 6 Feb. 27 Ch4_HiReflecMult.ppt
High Order Reflections from a Multilayer Coating Measured Calculated internal interference of incoming and outgoing waves Reflectivity 1 1 1 1 2 1 3 1 4 1 5 m = 1 2 3 W/C multilayer 22 layer-pairs d = 36.1 Å λ = 1.54 Å 4 5 E 2 4 3 2 1 1 6 1 7 2.5 5 7.5 1 12.5 Scattering angle 2θ ( ) 1d Distance from surface (in periods) (Courtesy of Y. Wu and J. Underwood.) Ch4_HiOrdrReflc.ai
SOFT X-RAY OPTICS Eberhard Spiller SPIE (1994) Univ. California, Berkeley Multilayer Interference Coating, Scattering, Diffraction, Reflectivity, EE29F, 6 Feb. 27 Ch4_SpillerBook.ai
An Angular Scan of a Multilayer Mirror Performs a Fourier-Transform of the Density Profile Univ. California Berkeley Multilayer Interference Coating, Scattering, Diffraction, Reflectivity, EE29F, 6 Feb. 27 Ch4_AngulrScan.ppt
Multilayer Interface Mirrors Computational Model 1(Vacuum) 2 (Material A) 3 (Material B) E 1 θ E 2 R E 1 R E 2 t A t B z x j i E j 1 Ej R E j 1 Layer pair N j R E j j + 1 n 2 (A) n 1 (B) n substrate With refractive index n: n n = 1 δ + iβ = 1 a r e λ 2 (f 1 if 2 ) 2π E n Layer pair l (Courtesy of J. Underwood) www.cxro.lbl.gov Ch4_MultlyrIntrfMir.ai
Atomic Scattering Factors for Silicon (Z = 14) σ a (barns/atom) = µ(cm 2 /g) 46.64 E(keV)µ(cm 2 /g) = f 2 1498.22 Energy (ev) f 1 f 2 µ(cm 2 /g) µ(cm 2 /g) 3 3.799 3.734E 1 1.865E+4 7 2.448 5.71E 1 1.22E+4 1 5.657 4.58E+ 6.862E+4 3 12. 6.439E+ 3.216E+4 7 13.31 1.951E+ 4.175E+3 1 13. 1.7E+ 1.62E+3 3 14.23 1.961E+ 9.792E+2 7 14.33 4.24E 1 9.75E+1 1 14.28 2.135E 1 3.199E+1 3 14.2 2.285E 2 1.141E+ 1 7 1 5 1 3 1 1 f 1 f 2 15 1 5 5 1 1 1 1 1 1 1 1 1 1 Silicon (Si) Z = 14 Atomic weight = 28.86 1 1 Edge Energies: 1 1 1 E (ev) (Henke and Gullikson; www-cxro.lbl.gov) 1 K 1838.9 ev L 1 149.7 ev L 2 99.8 ev 99.2 ev L 3 1 2 1 1 1 E (ev) 1 Ch2ApC_Tb1F7_Sept5.ai
Atomic Scattering Factors for Molybdenum (Z = 42) σ a (barns/atom) = µ(cm 2 /g) 159.31 E(keV)µ(cm 2 /g) = f 2 438.59 Energy (ev) f 1 f 2 µ(cm 2 /g) µ(cm 2 /g) 3 1.71 5.292E+ 7.736E+4 7 19.38 4.732E+ 2.965E+4 1 14.2 1.124E+ 4.931E+3 3 4.69 1.568E+1 2.292E+4 7 31.41 1.819E+1 1.14E+4 1 35.15 1.188E+1 5.21E+3 3 35.88 1.366E+1 1.997E+3 7 42.11 3.493E+ 2.189E+2 1 41.67 1.881E+ 8.248E+1 3 42.4 1.894E+ 2.769E+1 1 6 1 5 1 4 1 3 1 2 1 1 1 1 1 1 E (ev) Edge Energies: (Henke and Gullikson; www-cxro.lbl.gov) 1 f 1 f 2 6 5 4 3 2 1 1 1 1 1 1 1 1 1 1 1 E (ev) K 19999.5 ev L 1 2865.5 ev M 1 56.3 ev N 1 63.2 ev L 2 2625.1 ev M 2 411.6 ev N 2 37.6 ev L 3 252.2 ev M 3 394. ev N 3 35.5 ev M 4 231.1 ev 227.9 ev M 5 Molybdenum (Mo) Z = 42 Atomic weight = 95.94 1 AST 21/EECS 213 Univ. California, Berkeley Ch2ApC_Tb1F12_June28.ai
Optimized Reflectivity with Thin High-Z Layers (4.7) (4.8) high-z low-z high-z low-z high-z low-z high-z (Vinogradov and Zeldovich, 1977) (also see Borrmann, 1941) Sharp interfaces needed for scattering Thin high-z layer to minimize absorption Low-Z layer best as a spacer Ch4_OptomizReflcty.ai
Computed Reflectivity of a W/C X-Ray Multilayer Mirror Reflectivity 1..8.6.4.2 W/C λ = 8.34 Å d = 22.5 Å N = 1 Γ = 1/3 2 4 6 8 1 12 Glancing angle ( ) (Courtesy of J. Underwood and D. Solina) Ch4_ComputdReflec.ai
Mo/Si Multilayer Interference Coating Molybdenum as the scattering layer Silicon as the non-absorbing spacing layer Actually an exaggeration, the complex refractive index of each material plays a role in the reflection process The absorption edge Si-L 3 = 99.2 ev (12.5 nm) Higher photon energies are absorbed in Si, lower photon energies (longer wavelengths) are not. Typically λ = 13.4 nm or more. Molybdenum has relatively good scattering properties in this photon energy (wavelength) region, with limited absorption. Univ. California Berkeley Multilayer Interference Coating, Scattering, Diffraction, Reflectivity, EE29F, 6 Feb. 27 Ch4_MultilyrIntrCtg.ppt
A High Quality Mo/Si Multilayer Mirror N = 4 d = 6.7 nm Courtesy of Sasa ˇ Bajt (LLNL) Ch4_HiQualtyMoSi.ai
High Reflectivity, Thermally and Environmentally Robust Multilayers Coatings for High Throughput EUV Lithography Univ. California Berkeley Multilayer Interference Coating, Scattering, Diffraction, Reflectivity, EE29F, 6 Feb. 27 Ch4_MoSi_ctngs.1.2.ppt
Multilayer Mirrors Have Achieved a Reflectivity of 7% Reflectivity.8.7.6.5.4.3.2.1 Mo/B 4 C/Si 7% at 13.5 nm FWHM =.55 nm 5 bilayers. 12. 12.5 13. 13.5 14. 14.5 Wavelength (nm) Courtesy of Sasa ˇ Bajt (LLNL) Ch4_ReflectCurv7.ai
Sputtered Deposition of a Multilayer Coating Table rotation Mirror substrate Planetary rotation Rotating table Mirror substrate Mirror substrate Mirror substrate Table grounded Sputtered atoms (target material) moving toward table Deposited thin film Shadow mask Shadow mask Sputtered particles Plasma ions moving towards cathode (target material) Plasma containing magnetic flux lines Target erosion area Target material (cathode) Target for high-z material Erosion area S N S S Target housing (negative cathode) Magnetic flux lines confining plasma Target for low-z material Magnetron Target housing Ch4_SputtrdDepo.ai
DC Magnetron Sputtering is Used to Reliably Deposit Multilayer Coatings of Predictable Center Wavelength and Excellent Uniformity Substrates mounted on a rotating platter are swept across each sputter source sequentially to form the multilayer. Modulating the platter velocity provides precision control of radial thickness distribution and absolute film thickness. The substrate is also spun fast about its own axis for azimuthal uniformity. Spinner motor assembly Vacuum chamber Substrate platter Substrate Mo Magnetron sources Si (Courtesy of Jim Folta, LLNL) Extreme Ultraviolet Lithography Univ. California, Berkeley Multilayer Interference Coating, Scattering, Diffraction, Reflectivity, EE29F, 6 Feb. 27 Ch4_DCmagntrn.ai
Buried, Trace Amounts of Iron in a Defective Silicon Solar Cell Sample Focal spot 1 µm D focal spot Multilayer coated elliptically bent mirrors Aperture e Synchrotron Source (white radiation) M 2 y x Scanning stage Fluorescent x-rays M 1 Solid state Si (Li) detector Fe contaminated solar cell 32 fg/µm 2 (Courtesy of A. Thompson and J. Underwood, LBNL; and R. Holm, Miles Lab) 1. mm 1.4 mm Ch4_F14VG.ai
Microprobe Analysis of Contaminated Soil Ca Cr Fe pg/µm 2 2.4 1. 1 1 mm 1 mm Ni Cu.2 pg/µm 2 Zn.1 pg/µm 2.3 pg/µm 2 (Courtesy of T. Tokunaga; and A. Thompson, LBNL) Ch4_F15VG.ai
High Resolution X-Ray Diffraction Under High Pressure Using Multilayer Coated Focusing Optics Synchrotron radiation e Aperture Diamond anvil cell Focused x-rays Sample under pressure ( 3 GPa) Gasket Pressure medium 1 16 kev x-rays Multilayer coated mirrors Scattered x-rays Film Diamond anvil cell 2θ H.K. Mao et al., Science 277, 122 (29 Aug. 1997) Nature 396, 741 (24 Dec. 1998) Ch4_F16aVG.ai
NATURE 396, 741(24/31 DECEMBER 1998) www.nature.com Ch4_ElasticyRheolgy.ai
Recent Progress in Multilayer Mirrors Peak reflectance (%) 8 7 6 5 4 3 2 1 Near-Normal Incidence Multilayer Mirrors Sc Ti V C H 2 O window Si Au 1 1 Wavelength (nm) RecentProgMultiilyrMir.ai
The Cassegrain Telescope Sun Convex secondary mirror Concave primary mirror Film or CCD Ch4_CassegrainTele.ai
EUV Image of the Solar Corona Showing Loops Near the Solar Limb http://vestige.imsal.com/trace (Courtesy of L.Golub, Harvard-Smithsonian and T. Barbee, LLNL) λ = 17.3 nm (71.7 ev) Ch4_F1VG_Sept5.ai
Dynamics of the Solar Corona (Courtesy of L. Golub, Harvard-Smithsonian) Ch4_DynamicsSolar.ai
Extreme Ultraviolet (EUV) Lithography Reflective mask Absorber pattern λ = 13 nm Multilayer mirror 4:1 reduction optics, aspheric, multilayer coated Wafer to record 5 nm or smaller features, over cm 2 dimensions 5 6 7 Extreme Ultraviolet Lithography Ch4_F11VG.ai
Polarization Studies of Magnetic Materials (a) Fe/Cr transmission sample Ι H Detector NdFeB magnets D Laterally graded W/B 4 C multilayer mirror (b) A B A B A B A B A Substrate (c) Reflectance (arb. units).7 22 mm Center +22 mm.6.5.4.3.2.1. 66 68 7 72 74 ω (ev) (d) Rotation (degrees) 6 4 2 2 H parallel k 4 H anti-parallel k 6 68 69 7 71 72 73 ω (ev) (Courtesy of J. Kortright and M. Rice, LBNL; and R. Carr, Stanford) Ch4_PolarizStudies.ai