X-ray spectroscopy and metrology

with high-harmonic sources

Peter M. KrausAdvanced Research Center for Nanolithography (ARCNL), Amsterdam, The Netherlands.EUV Lithography Source Workshop, 06.11.2018 – HiLASE, Prague, Czech Republic.

EUV lithography requires new XUV sources

Understand EUV (13.5 nm) interactions to

improve masks, pellicles, mirrors, resists…

Y. Zhang et al., J. Micro Nanolith. MEMS

MOEMS 16, 023510 (2017)

Ulrafast XUV and soft x-ray spectroscopy

Resolve structures during lithography and

after production with sub-nm precision

L. Li et al., Chem. Soc. Rev., 2017, 46, 4855

Broadband XUV and soft x-ray imaging

We need an ultrafast, coherent, table-top XUV/soft x-ray source

Solution: High-harmonic generation (HHG)

3

Space

20 eV

= 60 nm

50 eV 120 eV

= 10 nm^^

argon atoms

1300 nm

~ 1 mJ

~1014 W/cm2

High-harmonic generation (HHG): Converting many IR-photons into one

XUV-photon

High-harmonic generation

Figure from:

P. M. Kraus, H. J. Woerner, Angew. Chem. 57,

5228 (2018).

Three-step model of HHG:

P. B. Corkum, PRL 71, 1994 (1993)

J. L. Krause, K. J. Schafer, K. C. Kulander,

PRL 68, 3535 (1992)

Quantum theory of HHG:

M. Lewenstein et al., PRA 49, 2117 (1994)

Three-step model of HHG

- 1 -

Ionization

E

0

- IP

3.17 Up

Core

Electron

mean field

Active

electron

r

- 2 -

Propagation

- 3 -

Recombination

XUV

emission

Typical parameters:

800 nm

~ 1 mJ

~ 1014 - 1015 W/cm2

Imaging needs in nanolithpgraphy

Lensless imaging with x-rays

from HHG

Compared to a conventional

microscope, the lenses are

replaced with a computer

algorithm

Collaboration with Stefan Witte

& Kjeld Eikema (ARCNL)

Needs in lithography: Short

wavelength, high average

power

Demonstrated HHG sources

S. Haedrich et al., J. Phys. B 49, 172002 (2016).

0.8 1.4 2.0e- transit time / fs

frequency

H9, H11, …. …, H31, H33, ….

time / fs0 0.5 1 1.5 2 2.5

ele

ctr

on d

ispla

cem

ent

laser

ele

ctr

ic fie

ld 800 nm

Longer driving wavelengths in the mid-infrared (MIR) allow to generate

higher x-ray energies with a lower average power through HHG

time / fs0 1 2 3 4la

ser

ele

ctr

ic fie

ld

0.5 1.5 2.5 3.5

1300 nm

1.2 2.2 3.2e- transit time / fs

frequency

H9, H11, …. …, H67, H69, ….

P. M. Kraus, H. J. Wörner, Angewandte Chemie (2018)

MIR driver for cutoff extension in HHG

T. Popmintchev, Science, 2012

HHG up to 1.6 keV has already been demonstrated

High x-ray flux requires a high repetition rate, few-cycle MIR source

Soft x-ray high-harmonic generation

Technical realization of new HHG source

Amphos pump laser:

1 kW, 20 mJ, 50 kHz,

1-2 ps, 1064 nm

MIR-OPCPA

100 W, 2 mJ, 50 kHz,

35 fs, 2000 nm, CEP stable

The OPCPA will drive a unique EUV/soft x-ray HHG source (<600 eV / 2 nm)

which will serve many collaborations within and outside of ARCNL.

Expectations for HHG-source at ARCNL

New HHG source

at ARCNL

S. Haedrich et al., J. Phys. B 49, 172002 (2016).

EUV lithography requires new XUV sources

Understand EUV (13.5 nm) interactions to

improve masks, pellicles, mirrors, resists…

Y. Zhang et al., J. Micro Nanolith. MEMS

MOEMS 16, 023510 (2017)

Ulrafast XUV and soft x-ray spectroscopy

Resolve structures during lithography and

after production with sub-nm precision

L. Li et al., Chem. Soc. Rev., 2017, 46, 4855

Broadband XUV and soft x-ray imaging

We need an ultrafast, coherent, table-top XUV/soft x-ray source

Solution: High-harmonic generation (HHG)

What happens in lithography?

New photoresists: tin-oxo cage compounds

High EUV sensitivity and finesse

?exposure

t = ?

What happens in the photoresists?wafer

photoresist

mask

exposure

Y. Zhang et al., J. Micro Nanolith. MEMS MOEMS 16, 023510 (2017)

Mechanisms in photoresists

Processes in photoresists after exposure:

- Metal-carbon bond dissociation

- Oxidation state change

- Spin state change

W. D. Hinsberg and S. Meyers Proc. of SPIE Vol. 10146, 1014604-1 (2017)

Principles of ultrafast EUV spectroscopy

Core-level reflectivity is element,

oxidation-state, and spin-state specific.

Ideally suited to unravel the complex

chemical dynamics of photoresists.

sample

HHG

target

metal

filter

EUV

attosecond

probe-pulse

VIS/DUV

femtosecond

pump-pulse

atomic-like

core level

HOMO

LUMO

energy

metal

filter EUV gratingXUV-sensitized

CCD camera

C. J. Kaplan, P. M. Kraus et al.,

PRB 97, 205202 (2018)

The XUV reflectivity measures the joint density of states

between the core level and CBs

GX U,KGL

3d3/2 (-29.9 eV)

3d5/2 (-29.3 eV)

D1

L3

L3D1

Reflectivity measures density of states

Iterative fit

𝜀 = 𝜀𝑐 +𝜔𝑝𝑒2

𝜔𝑒2 −𝜔2 − 𝑖𝜔𝛾

Femtosecond dynamics in germanium

C. J. Kaplan, P. M. Kraus et al.,

PRB 97, 205202 (2018)

DR/R

real imag.

Carrier Positions

Real part of the dielectric

function tracks carrier position

Imaginary part of the dielectric function

tracks carrier population in p-states

Carrier Amplitudes

Measuring the XUV dielectric function

C. J. Kaplan, P. M. Kraus et al.,

PRB 97, 205202 (2018)

Holes:

t1 = 0.6 ps: intravalley scattering

t2 = 4.8 ps: optical phonon decay

Electrons:

t1 = 0.4 ps: G-X & L-X scattering

t2 = 5.5 ps: optical phonon decay

Holes:

t = 3.2 ps: Carrier diffusion

and Auger recombination

Electrons:

t = 3.2 ps: Carrier diffusion

and Auger recombination

Carrier Positions Carrier Amplitudes

XUV transient reflectivity is a detailed and simultaneous probe of

carrier dynamics.

Time scales of carrier relaxation

C. J. Kaplan, P. M. Kraus et al.,

PRB 97, 205202 (2018)

Status at ARCNL: Spectroscopy of resists

2-color HHG (driving with 800+400 nm)

Currently measuring first broadband EUV absorption spectra.

Ongoing collaboration with Sonia Castellanos and Fred Brouwer.

XUV absorption of Ti-based resists

Tran

smis

sio

n23 eV

M2,3 edge3p -> LUMO33 eV

45 eV

Pixel

Transmission spectrum through TiO2

Observation of Ti M2,3-edge in photoresist product

Thank You!

HHG and EUV science group at ARCNL:Filippo Campi Reinout JaarsmaSylvianne Roscam Abbing Faegheh Sajjadian Maarten van der Geest (not in picture)Najmeh Sadegh (not in picture)

Ongoing collaborations at ARCNL:Stefan WitteKjeld EikemaSonia CastellanosFred Brouwer