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Laser-

Laboratorium

Göttingen e.V.

Laser-Laboratorium Göttingen e.V.

Hans-Adolf-Krebs Weg 1

D-37077 Göttingen

Table-top EUV/XUV source for

metrology applications

NEXAFS spectroscopy

Klaus Mann

Dept. Optics / Short Wavelengths

2

Dept. “Optics / Short Wavelengths”

Beam and Optics Characterization (DUV)

Beam propagation

Wavefront

coherence

M²

Optics test (351…193 nm)

(Long term) degradation (109 pulses)

Non-linear processes

LIDT

Absorption / Scatter losses

Wavefront deformation

EUV/XUV technology

Source & Optics

Metrology

Material interaction

Types of laser produced plasmas

Target material Solid Liquid Gas

Advantages + conversion

efficiency

+ Small plasma

(~50µm)

+ conversion

efficiency

+ mass limited,

small target

(~50µm)

+ „clean“ (no

debris)

+ high flexibility

+ high stability

+ low effort

Disadvantages unflexible

„dirty“ (debris)

high effort

debris:

„snowballing“

relatively low

brilliance

size ~300µm

3

EUV/XUV radiation:

Lab source for metrology

Nd:YAG

Laser

EUV source

chamber

Laser power supply

Spezifications:

- Wavelength: 1 - 20nm

- Pulse energy (Xe): 4mJ (4 sr, 2%BW)

- Conversion eff.: 0.45% (Xe)

- Pulse length: 6ns

- Plasma size: ~ 300µm

EUV: 10…20nm XUV: 1…10nm

pulsed Xenon gas jet

laser

EUV

Pinhole

camera

• Univ. Prag

• Univ. Göttingen

• Max-Planck Inst.

5

LLG-Activities Based on

EUV LPP Source

Direct structuring Reflectometry

NEXAFS spectroscopy XUV microscopy

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 8510

-4

10-3

10-2

10-1

100

Ref

lect

ivit

y

Sample angle

6

Ablation / damage thresholds

@13.5nm

Laser driven EUV/XUV plasma source setup

1.2 J/cm2 (@ 13,5 nm, 2 % bandwidth)

7.4 J/cm2 (filtered by 2 Mo/Si mirrors)

Damage thresholds of

mirrors / substrates single-pulse damage

F. Barkusky, K. Mann et al., Optics Express 18, 4347 (2010)

F. Barkusky, K.Mann et al., J. Appl. Phys. 101, 124908 (2007)

Integrated source and optics system:

EUV direct structuring

1µm PMMA

Color Centers in LiF

Resolution 130nm

Period 1.4µm

Schwarzschild objective

@13.5nm (Mo/Si):

PMMA

EUV Diffraction experiment

pure EUV radiation !

(@ 13.5 nm, 2% BW)

- Pinhole ( 50µm) behind plasma

- mesh before objective

diffraction pattern imprinted on PMMA

= Near-edge x-ray absorption fine-structure

200 250 300 350 400 450

0

2000

4000

6000

8000

10000

12000

14000

0,0

0,2

0,4

0,6

0,8

1,0

Inte

nsity [C

CD

-Co

un

ts]

Photonenenergy [eV]

without sample

with Polyimid (d=200nm)

Transmission Carbon (CXRO)

Tra

nsm

issio

n

Plasma in Kr gas jet „water window“ / Polyimide (d=200nm):

Absorption in unoccupied molecular orbitals

„Fingerprint“ of molecules

Soft x-rays with lab source:

NEXAFS Spectroscopy

Carbon

K-edge

surface-sensitive chemical analytics

polychromatic concept

280 290 300 310 320

0,0

0,5

1,0

1,5

2,0

*C-N

*C=C

*C=O

*C=O

Op

tisch

e D

ich

te [a

.u.]

Photonen-Energie [eV]

*C=C

C. Peth, K. Mann et al.,J. Phys. D 41 (2008) 105202

Polyimide

60 pulses

Synchrotron data

(J. Stöhr):

Setup of NEXAFS Spectrometer

Table-top system

„Single-shot“

Pump-probe exp.

XUV plasma (Kr)

with pinhole camera

Single pulse NEXAFS spectra

NEXAFS spectroscopy on thin films

Lipid membranes (carbon K-edge)

E. Novakova, C. Peth, K. Mann, T. Salditt et al.: Biointerphases, 3 (2008) FB44

285 290 295 300 305 310 315

0

1

2

3

4

Optic

al d

ensi

ty

Photon energy (eV)

C=C*

DOPS

DOPC

DMPC

4,4 4,3 4,2 4,1 4 3,9

Wavelength [nm]

(T. Salditt)

NEXAFS spectra of PMMA

PLD: PMMA films (200nm)

Softer as bulk material shorter polymer chains

C=C bonds visible

280 285 290 295 300 305 3100,0

0,2

0,4

0,6

0,8

1,0

*C-O

*C=O

*C=C

optical density (

a.u

.)

photon energy (eV)

PMMA, untreated

PMMA, UV irradiated (5h)

*C-C

UV irradiation

Chemical changes :

Loss of C=C bonds

Increase of C=O bonds

repolymerization

bulk material

B. Fuchs, P. Großmann, K. Mann, H.U. Krebs et al., Appl. Phys. A98, 711-715 (2010)

NEXAFS spectrum PCMO

14

300 400 500 600 700 800 900 10001,0

1,1

1,2

1,3

1,4

1,5

1,6

1,7

1,8

1,9

2,0

Optical T

hic

kness [a.u

.]

Photon-Energy (eV)

NEXAFS-Spectrum PCMOCaL 2,3

NK

OK

MnL 2,3

PrM 4,5

▲Perovskit-type Manganate

Pr1-xCaxMnO3

525 530 535 540 545 550 555 5601,0

1,1

1,2

1,3

1,4

Optica

l T

hic

kn

ess

Photon-Energy /eV

NEXAFS-Spektrum PCMO, O K-Kante

EELS Referenzdaten

: Pr, Ca

: O

: Mn

High-Tc superconductor

Every element visible

Agreement with reference

pump-probe experiments Radiation-induced

phase transition (~100K)

O K-edge

(S. Techert)

XUV source improvements:

Comparison: ns – ps laser

Xe (Z = 54)

Single pulse XUV spectra

200 400 600 800 100010

1

102

103

104

200 400 600 800 100010

1

102

103

104

200 400 600 800 1000

101

102

103

200 400 600 800 100010

2

103

104

200 400 600 800 100010

2

103

104

200 400 600 800 100010

2

103

104

Photon energy (eV)

Single-Pulse - Max. Laserpulse-Energy - Al filteredNitrogen Oxygen Neon

Photon energy (eV) Photon energy (eV)

Photon energy (eV)

Argon Krypton Xenon

Photon energy (eV) Photon energy (eV)

Single pulse XUV spectra

Single pulse XUV spectra

Single pulse spectra:

O (Z = 8) Ne (Z = 10) N (Z = 7)

Ar (Z = 18) Kr (Z = 36)

8ns

450mJ

150ps

380mJ

Peak brillance of isolated N line @ = 2.88nm:

6*1017 (ns-Laser) 1.2*1020 Ph./(s mrad2 mm2 0,1%BW) (ps-Laser)

The barrel shock – Schlieren images

10-3mbar

1 bar

Nitrogen

10bar

ambient

pressure:

16

500µm

The barrel shock

17

Nitrogen

10 bar

Helium

170 mbar

Wavefront

Density

Nitrogen

10 bar

Helium

170 mbar

18

Nitrogen

10 bar

Vacuum

~10-3 mbar

500 µm 500 µm

Plasma generation with/without the barrel shock

Nitrogen

10 bar

Helium

170 mbar

19

Nitrogen

10 bar

Vacuum

~10-3 mbar

500 µm 500 µm

Plasma generation with/without the barrel shock

Enhancement of particle density in gas jet:

increased brillance from shock wave

Pinhole camera image of Nitrogen plasma p=10bar / Ti-filtered

pamb = 10-3 mbar pamb = 170 mbar

Summary and Outlook

EUV / XUV source

Compact, clean, reliable

Line or broad-band radiation (1…20nm)

EUV: reflectometry, direct structuring / ablation studies

XUV: NEXAFS for chemical surface analysis

Further increase of brilliance / higher photon energies

Entire spectrum in single pulse / pump-probe

scanning spectro-microscopy

• Dr. B. Schäfer

• Dr. A. Bayer

• Dr. U. Leinhos

• Dr. F. Barkusky

• J.O. Dette

• M. Lübbecke

• M. Reese

• B. Flöter

• P. Grossmann

• M. Olschewski

• S. Döring

• T. Mey

• J. Sudradjat

Thank You !

Coworkers:

Outline

1. Table-top EUV/XUV source

- experimental

2. Metrology applications

- reflectometry

- Damage of EUV optics

- NEXAFS spectroscopy

3. Source improvements

4. Characterization of EUV/XUV radiation (FLASH)

- wavefront measurement / Hartmann(-Shack) sensor

- optics alignment

23

24

Hartmann-Shack wavefront sensor:

wavefront:

Wavefront w(x,y)

= surface Poynting-Vektor S(x,y)

(ISO 15367-2)

directional

distribution

intensity

distribution

B. Flöter, K. Mann, K. Tiedtke et al. NIM A 635, S108–S112 (2011)

Hartmann

plate

EUV/XUV

Beam

Beam characterization of

Free Electron Laser FLASH

EUV-Hartmann sensor: Spot distribution:

Adjustment of

beam line optics:

= 5 – 30nm

Accuracy:

• ~ /15 wpv for EUV

26

Ablation / damage thresholds

@13.5nm

Laser driven EUV/XUV plasma source setup

1.2 J/cm2 (@ 13,5 nm, 2 % bandwidth)

7.4 J/cm2 (filtered by 2 Mo/Si mirrors)

Damage thresholds of

mirrors / substrates single-pulse damage

F. Barkusky, K. Mann et al., Optics Express 18, 4347 (2010) (OSA Spotlight)

Peak brillance of laser plasma source

400 450 500 550 600 650 700

0

10000

20000

30000

40000

50000

60000

N VII 1s2-1s5p

N VII 1s2-1s4p

N VI 1s2-1s6p

N VI 1s2-1s5p

N VII 1s2-1s3pN VI 1s

2-1s4p

N VII 1s2-1s2p

N VI 1s2-1s2p

CC

D-C

ounts

Photonenenergie (eV)

Stickstoff - Einzelpuls - Al gefiltert

N VI 1s2-1s3p

Isolated N VI 1s2-1s2p line @ 2.8787nm (Ti filtered)

Peak brillance [Photons/(s mrad2 mm2 0,1%BW)]

ns-Laser: 6*1017 (LLG, T. Wilhein)

ps-Laser: 1,2*1020 (LLG)

NEXAFS-Spektrum bisDMA

06.12.2011 Peter Großmann 28

Dünne Schichten bisDMA (Weichmacher)

Beeinflussung Polymerkettenlänge z.B. PMMA

Suche nach optimalem PLD – Parametersatz

Variation Target - Substratabstand

Parameter-Abhängigkeit der

C=C Bindungen

C=C Bindungen als Maß für die

Unversehrtheit des bisDMA

Kürzerer Abstand besseres

Ergebnis?

Weitere Untersuchungen nötig 280 285 290 295 300 305 310 315 320

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

*C=C

*C=C

*C=O

Optis

che D

ichte

(b. E

.)

Photonenenergie / eV

bisDMA, Abstand 30mm

bisDMA, Abstand 40mm

bisDMA, Abstand 50mm

*C-C

*C-O

Compact NEXAFS spectrometer

30

► EUV Reflectivity

of 75 nm thick

carbon layer

EUV reflectometry

10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.00

1000

2000

3000

4000

5000

6000

7000

Oxygen spectrum

Mo/Si filter mirror

Inte

nsi

ty a

.u.

Wavelength [nm]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Ref

lect

ivit

y0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85

10-4

10-3

10-2

10-1

100

Ref

lect

ivit

y

Sample angle

EUV spot on sample

@ =13nm:

Specifications: - wavelength: 12.98nm (oxygen line)

- angular resolution: 0.3°

- angular range: 1° - 85°

- dynamic range: 4 orders of mag.

Mo/Si

multilayer

mirrors

@13nm

R~60%

„Water window“ (2,2nm – 4,4nm)

31

2,0 2,5 3,0 3,5 4,0 4,5 5,0

0,1

1

10

O: 2,28 nm

Ti: 2,73 nm

N: 3,0 nm

Ca: 3,58 nm

C: 4,36 nm

Ti N

Ca

H2O

C

Ab

so

rptio

nle

ng

th /

µm

Wavelenght /nm

▼Absorption edges

▼Soft x-ray microscopy

D. Attwood