Joe Arko Advanced Photon SourceRalu DivanKurt GoetzeTim MooneyDavid PatersonStefan VogtPetr IlinskiShenglan Xu

Sean Frigo Northern Arizona UniversityCornelia Retsch Saint-Gobain Sekurit DeutschlandNathan Krapf University of Chicago

Steve Wang Xradia CorporationWenbing Yun Xradia CorporationErik Anderson CXRO, Lawrence Berkeley National LaboratoryFranco Cerrina CXRL, University of Wisconsin at Madison

Many thanks to ...

Soft X-ray Microscopy at the APS

Ian McNulty

Argonne National Laboratory

Wednesday, 9 October 2002

APS

Summary

Motivation

APS efforts

Scanning microscopy

Flash methods

Future

APS

1-4 keV: access most of periodic table

K

L

M

M

APS

Materials science

• Nondestructive in situ imaging of buried structures

• Visible/electron-opaque samples, less charging than with electrons

• Contrast at K,L,M-edges in industrially important materials(AI, Si, Ti, Cu, Ga, Ge, As, Sm, Eu, Gd, W, Au, . . .)

• Study electromigration and fabrication defects in chip interconnects

Biology

• Better resolution than optical, less damage than electron microscopy

• Specimens can be initially living, wet, unstained, and in air

• Natural Na, Mg, P, S, Ca contrast in this energy range

Environmental science

• Study S in soils, fossil fuels, catalyst sulfidation, lubricants

• Chemical as well as elemental contrast

APS

1-4 keV x-rays: applications

APS

Soft x-ray microscopy at APS

Magnetic materials 4-ID-C (J. Freeland)

XANES PEEM

MCD, MLD PEEM, scanning (future)

Materials, biology 2-ID-B (D. Paterson)

Transmission scanning, holography, full-field

Fluorescence scanning

Tomography scanning

Microdiffraction scanning

APS

PEEM images provide direct map of chemical and magnetic structure

1 m x 1 m x 15 nm Conanodots on Al substrate(as dep., no field history)

Chemical map (Co bright)

Magnetic map (M bright)

1 m

Beam direction

PEEM optics

Co

Chemical and magnetic microscopy at 4-ID-C

J. Freeland, D. Keavney, R. Winarski (APS)J. Shi, W.C. Uhlig (Univ. Utah)

APS

2-ID-B intermediate-energy beamline

Monochromaticity ~500 typ., > 3000 peak

Coherent area 50 m 50 m

Coherent flux 2 105 ph/m2 /s/0.1% BW

Focused flux 4 107 ph/s/0.1% BW 50 nm spot2 108 ph/s/0.1% BW 150 nm spot

APS

Scanning x-ray microscope

rotation stage

coarse/fine scan stage

avalanche or PN junction photodiode

sample on support

order-sorting aperture

zone plate

coherent x-rays

VME crate and workstation

preamp and discriminator

Ge detector

APS

Zone Plates

MaterialRadiusCentral stop radiusZone thicknessFinest zone widthTransverse resolutionFocal length (1.83 keV)Depth of field ( " " )Meas. Efficiency ( " " )

Au Au Ni Ni38.5 40 45 49 - - - 20420 650 110 130100 50 45 40122 61 55 4911.4 5.9 6.0 5.872 18 15 1220 12 2.5 3.0

m µm nm nm nm mmm %

Sample Stage (XYZ)

Linear rangeLinear resolutionLinear velocityAngular rangeAngular resolutionMax scan speed

Coarse

2550023600.0010.1

Fine

0.10.8203600.140.1

2-ID-B SXM specifications

mmnmmm/sdegreesdegreesms/pixel

APS

Contrast of a 100-nm Al wire on 1 µm of Si

APS

STXM image at 1553 eV. Al interconnects becometransparent below Al 1s edge (1559 eV), whereas W vias joining interconnects still appear dense.

Elemental contrast in Al/W/Si chips

STXM images of two-level Al/W/Si test structureat 1563 eV. SiO2 substrate was thinned to ~5 µm.Sample courtesy of DEC.

Steve Grantham Nat'l Inst. of Standards and TechnologyZachary LevineAndy Kalukin SAICMarkus Kuhn Intel Corporation

APS

Scanning nanotomography of AI/W/Si chips

Z. Levine, et al., Appl. Phys. Lett. 74, 150 (1999)Z. Levine, et al., J. Appl. Phys. 87, 4483 (2000)

3D Bayesian reconstruction oftwo-level structure at 1750 eV

Normal-incidence scanof electromigration void

3D reconstruction of ragged end of void

5 µm 1 µm 500 nm

APS

Nanoscale metrology in Cu/W/polyimide chips

(a) Schematic side view of a two-level Cu/W test structure. (b) STXM image at normal incidence. (c) Elevated surface plot. Sample courtesy of IBM.

Comparison of various line scans through structure

X. Su, et al., Appl. Phys. Lett. 77, 3465 (2000)

APS

1-4 keV x-rays: biological applications

• Natural contrast for nuclear and mitochondrial DNA at K-edge of P (2149 eV)

• Probe cell ion transport and membrane permeability at K-edges of Na (1.09), Mg (1.28), K(3.82), Ca (4.04 keV)

• Co-locate lighter elements with trace metals mapped by hard x-ray microscopy, at higher resolution

• Study chemical speciation of important inorganic elements (Mg, Al, Si, Ca), e.g. in marine organisms

APS

Phosphorus XANES

P K fluorescence from NaPO4

P 1s absorption spectra

APS

Simultaneous transmission, fluorescence detection

Gd 3d5/2, 3d3/2Si 1s

APS

• Cell is transfected with TiO2-DNA nanocomposites

• DNA targets specific chromosomal region

• TiO2 photocleaves DNA strands upon illumination

• Potential use in gene therapy

5 m

2.2

0.0

g/cm2

5.8

0.0

g/cm2

TiO2-DNA nanocomposites in mammalian cells

ZnTi

Map Ti distribution using x-ray induced K

fluorescence, to quantify success rate ofTiO2-DNA transfection and visualize target

Affinity of transfected DNA to ribosomalDNA causes nanocomposites to localizeto the nucleolus

G. Woloschak, I. Moric, T. Paunesku, N. Stojicevic(Radiation Biology Dept., Northwestern Univ.)

APS

Phosphorous absorption imaging

10 µm 5 µm 5 µm

Mouse PC-12 cell(fixed, dried)

Cell nuclei, separated by centrifugation(fixed, dried)

Energy 2170 eV

Step size 50 nm

Dwell 10 ms

Scan time 20 min

APS

Energy-resolved fluorescence mapping

5 µm

Whole mouse PC-12 cell (fixed, dried)Detergent wash, ethidium bromide stain

Transmitted Na K Br L

2 µm

APS

Nuclear contrast with P fluorescence

P K Si K

5 µm

Energy 2200 eV

Step size 150 nm

Dwell 1 s/pixel

Scan time 4 h

APS

What about radiation damage?

APS

Flash imaging methods

• HolographyUse x-ray optics to form reference wave and object illumination

• Full-field imagingUse x-ray optics to magnify sample image

• Diffraction with phase retrievalX-ray optics useful but not required

APS

Quantitative phase contrast by holography

B. Allman, A. Barty, P. McMahon,K. Nugent, D. Paganin, J. Tiller(Dept. of Physics, Univ. Melbourne)

B. Allman, et al., JOSA A17, 1732 (2000)J. Tiller, Ph.D. Thesis, U. Melbourne (2001)

Hologram of ~1 µm Al sphereson 100 nm formvar membrane

Difference between twoholograms at different foci

Reconstructed phase

APS

Full-field phase imaging

B. Allman, et al., JOSA A17, 1732 (2000)

Full-field image of ~2 µm spider silk

Difference between in-focus, defocused images

Reconstructed phase

APS

Phase imaging of optical fiber

APS

Phase nanotomography of Si AFM tip

3D reconstructions of real part of refractive index of projections.(a, b) Horizontal slices through tip. (c) Vertical slice. (d-f) Volume renderings. Measured = 5.0 ± 0.5 x 10-5 , calculated = 5.1 x 10-5.

P. McMahon, et al., Opt. Commun., in press

APS

Future developments

• Scanning microscope– New ZP on order (50 nm outermost zone, 450 nm Au)– Multiple SDDs to increase fluorescence acceptance– 2K x 2K fly scans

• Extend quantitative phase imaging to ~50 nm level– Improve alignment for d/dz series– Solve twin-image problem with TIE– Determine limits on coherent flux required

• 2-ID-B beamline– Multilayer gratings on order

APS

Conclusions

• 1-4 keV region highly attractive for x-ray microscopy

• 2-ID-B SXM is a workhorse instrument at APS– 50 nm (2D), 150 nm (3D) resolution– simultaneous transmission and fluorescence– Goal: reach photon limits near ~10 µs/pixel (transmission)

~0.1 s/pixel (fluorescence)

• Developing holography, coherent full-field imaging– Obtain quantitative absolute phase– Applicable to flash x-ray sources Beat radiation damage problem!