k λ NA Resolution of optical systems depends on the wavelength visible light λ = 500 nm Extreme ultra-violet and soft x-ray light λ = 1-50 nm

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1 Resolution of optical systems depends on the wavelength visible light λ = 500 nm Spatial Resolution = k λ NA EUV and SXR microscopy can potentially resolve full-field images with x smaller features than conventional visible microscopy Extreme ultra-violet and soft x-ray light λ = 1-50 nm

2 High resolution EUV and SXR microscopy at 3rd generation synchrotrons Short wavelength imaging at LBNL BEST SPATIAL RESOLUTION 15 nm Images downloaded from www-cxro.lbl.gov website W. Chao, et al., Nature 435, (2005).

Early imaging work using soft x-ray lasers Transmission mode imaging Imaging with a 4.48 nm collisional Ni-like Ta laser pumped by NOVA Spatial resolution of ~ 75 nm L.B.

Letters 17, 754 (1992) Reflection mode imaging Imaging with a 18.2 nm recombination laser Spatial resolution of ~ 0.7 µm D.S. DiCicco et al., Opt.

3 Early imaging work using soft x-ray lasers Transmission mode imaging Imaging with a 4.48 nm collisional Ni-like Ta laser pumped by NOVA Spatial resolution of ~ 75 nm L.B. DaSilva et al., Opt. Letters 17, 754 (1992) Reflection mode imaging Imaging with a 18.2 nm recombination laser Spatial resolution of ~ 0.7 µm D.S. DiCicco et al., Opt. Letters 17, (157) 1992 Radial spokes pattern TEM 200-mesh grid 20 deg grazing incidence x16 magnification IMAGING WITH OTHER TABLE-TOP SOFT-X-RAY SOURCES Incoherent droplet 3 nm Spatial Resolution 100 nm Berglund et al nm SXRL-JAERI- M. Kishimoto et al (2003) Spatial resolution ~200 nm. High Harmonic 13 nm Spatial Resolution > 200 nm M. Weiland et al. (2005)

4 Microscopes at CSU Imaging at λ=46.9 nm in transmission and reflection modes Imaging at λ=13 nm in transmission mode 20 µm 2 µm 500 nm

5 Table top 46.9 nm imaging based on capillary discharge laser microscope capillary-discharge laser ~ 70 cm Ne-like Ar capillary-discharge laser parameters: high pulse energy ( mj) 1.2 ns Pulse duration 1 4 Hz repetition rate high monochromaticity ( λ/λ < 10-4 ) capillary length: 18 and 27 cm (controls degree of spatial coherence)

6 Compact transmission mode microscope 46.9 nm laser laser beam Schwarzschild condenser Schwarzschild condenser objective zone plate sample sample objective zone plate CCD

Microscope optics Schwarzschild condenser (Lebedev

8 mm Focal distance f = 27 mm Num. Aperture NA = 0.

7 Microscope optics Schwarzschild condenser (Lebedev Physical Inst.- KhPI-Ukrane ) Specifications: Diameter M 1 D 1 = 50 mm Diameter M 2 D 2 = 10.8 mm Focal distance f = 27 mm Num. Aperture NA = 0.18 Throughput T = 1% New Schwarzschild condenser with improved Sc/Si multilayer coated mirrors. Total throughput ~16%.

$Microscope optics Objective: diffractive optics Strong absorption at λ=46.$

8 Microscope optics Objective: diffractive optics Strong absorption at λ=46.9 nm in most materials required the development of free standing zone plates and test patterns SEM images of objective and test pattern Zone Plate Parameters Outer zone width = 200 nm Numerical aperture (NA) = 0.12 Diameter = 0.5 mm Number of zones = 625 Focal distance = 2.14 mm Focal depth = 3.4 µm Circular Test Pattern: diameter = 200 µm smallest features = 100 nm substrate = Ni foil Fabricated by electron beam lithography at CXRO E. H. Anderson, IEEE JQE vol. 42, 27 (2006)

zones k: illumination and test dependent constant D. T.

9 Spatial resolution zone plate outermost zone width Re s. λ = k = 2k r NA r r: width of objective outermost zones k: illumination and test dependent constant D. T. Attwood, Soft X-rays and Extreme Ultraviolet Radiation

10 Resolution The constant k is test and illumination dependent Grating resolution M>26.6% M 2k 0.3 <k <0.5 Coherence parameter m = NA C /NA O (Grating test- half period) J. M. Heck, D.T. Attwood, et al., J. X-ray Sci. Tech. 8, 95 (1998)

11 46.9 nm image of a test pattern Circular test pattern 100 nm 10 sec exposure (10 laser shots at 1 Hz) 470 magnification 100 nm wide features in innermost ring 5 µm

120-150 nm spatial resolution obtained SXR Images of a zone plate 5 µm 1 µm 200 nm

5 % (Rayleigh-like modulation) Modeling indicates 120-150 nm spatial resolution. G.

12 nm spatial resolution obtained SXR Images of a zone plate 5 µm 1 µm 200 nm zone--width ~ 94 % modulation >> 26.5 % (Rayleigh-like modulation) Modeling indicates nm spatial resolution. G. Vaschenko et al Optics Letters vol 30, 2095 (2005) Intensity, a.u % Distance, µm

13 Reflection mode microscope images semiconductor chip 46.9 nm laser Image of polysilicon lines on Si-substrate CCD 30 sec exposure 470 magnification Objective zone plate r=200 nm Imaged area: ~ 60x40 µm CCD Schwarzschild Condenser 46.9 nm laser Test Pattern at 45º 5 µm Sample courtesy of AMD 10 µm

SXR imaging of polysilicon lines on Silicon 100 nm lines are visible 60 sec exposure - 750 magnification

14 SXR imaging of polysilicon lines on Silicon 100 nm lines are visible 60 sec exposure magnification 2 µm 100 nm lines 800 nm spaces 250 nm lines 250 nm spaces F. Brizuela et al., Opt. Express 13, 3983 (2005)

5µm lower coherence Advantage of single shot imaging: ease in

15 Single shot images but coherence effects are more notorious (a) (b) 27 cm capillary 18 cm capillary higher coherence 5µm 5µm lower coherence Advantage of single shot imaging: ease in the alignment of the system will allow time resolved measurements

46.9 nm microscope shrinks to desktop size

up 12 Hz repetition rate Improved condenser

incorporates: Controlled positioning of EUV

Remote imaging acquisition operation From EUV

16 46.9 nm microscope shrinks to desktop size EUV laser Microscope SXR laser output: 10 µj up 12 Hz repetition rate Improved condenser throughput: 16% To CCD Compact Microscope incorporates: Controlled positioning of EUV optics Visible lower magnification microscope Remote imaging acquisition operation From EUV Laser Schwarzschild Condenser Objective Zone Plate Object

17 Images of integrated circuits SXR Image of polysilicon lines on Silicon SXR Image of metal pattern on Silicon 5µm 250 nm lines and spaces 1 µm 170 nm half period structure 100 nm lines, 800 nm spaces 170 nm half period structure Exposure time: 20 3Hz

18 Zone plate 13 nm microscope operates in transmission mode λ= 13 nm Microscopy System 13 nm Laser CCD Sample Objective zone plate Condenser zone plate Laser in Microscope Laser

13.2 nm imaging system SXR Laser Parameters Power :1-2 µw Wavelength: 13.2 and 13.

7 Reflectivity of a typical Mo/Si multilayer 13.2 nm Objective zone plate r = 80 nm Δr = 50 nm Ø = 0.2 mm Ø = 0.1 mm NA = 0.

1 13.2 nm 13.9 nm 13.9 nm 0.0 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2 14.4 Wavelength, nm λ= 13.

19 13.2 nm imaging system SXR Laser Parameters Power :1-2 µw Wavelength: 13.2 and 13.9 nm Zone Plate Optics Parameters SEM Image of zone plate Condenser zone plate Ø= 5 mm Δr = 100 nm NA= Reflectivity of a typical Mo/Si multilayer 13.2 nm Objective zone plate r = 80 nm Δr = 50 nm Ø = 0.2 mm Ø = 0.1 mm NA = 0.26 NA = Gratings of decreasing linewidth are used to determine the spatial resolution Reflectivity nm 13.9 nm 13.9 nm Wavelength, nm λ= 13.2 nm illumination falls within bandwidth of Mo/Si coatings J.J. Rocca et al., Opt. Lett. Vol. 30, 2581 (2005); Y. Wang et al., Phys. Rev. A 72, 5 (2005) Gratings SEM image of test pattern E. H. Anderson, IEEE JQE vol. 42, 27 (2006)

20 13.9 nm imaging system offers Large Field of View Image of a test pattern obtained with 80 nm outer zone width objective lens; 6 sec exposure. 15µm 1 µm 20µm 60 nm wide lines

21 6 sec Exposure Time Images of 120 nm elbows λ = 13.9 nm r = 50 nm 30 laser pulses at 5 Hz 1 µm

90 nm dense lines 50 nm dense lines 1 µm Intensity, CCD Counts 100 80 60 40 20 38 nm 0 0.0 0.5 1.0 1.5 2.0 2.5 Distance, µm 0.5 µm G.

22 Spatial resolution of 38 nm with the 13.2 nm imaging system Images of dense line patterns obtained with 50 nm outer zone width objective lens; 20 sec exposure. 90 nm dense lines 50 nm dense lines 1 µm Intensity, CCD Counts nm Distance, µm 0.5 µm G. Vaschenko, et al Optics Letters, vol 31, 1214 (2006) 70 % Intensity Modulation of 38 nm 1:1 lines indicates spatial resolution is better than 38 nm Highest resolution achieved from table-top light-based microscope: 38 nm Highest resolution achieved from table-top light-based microscope: 38 nm

Nanoscale Imaging with Extreme Ultraviolet Lasers

Nanoscale Imaging with Extreme Ultraviolet Lasers C. Brewer *, G. Vaschenko, F. Brizuela, M. Grisham, Y. Wang, M. A. Larotonda, B. M. Luther, C. S. Menoni, M. Marconi, and J. J. Rocca. NSF ERC for Extreme