FOMFOM

Multilayer fabrication at FOMMultilayer fabrication at FOM

Fred Bijkerk, Eric Louis,Fred Bijkerk, Eric Louis,

Andre Yakshin, Robbert vd Kruijs, Erwin Zoethout, Sergiy Dobrovolsky, Malcom Wu,Andre Yakshin, Robbert vd Kruijs, Erwin Zoethout, Sergiy Dobrovolsky, Malcom Wu,

Ileana Nedelcu, Tim Tsarfati, Véronique Lohmann, Saskia Bruijn,Ileana Nedelcu, Tim Tsarfati, Véronique Lohmann, Saskia Bruijn,

Edward Maas, Santi Alonso vd Westen, Fabian Wahle, Kees Grootkarzijn, Peter Sallé, Edward Maas, Santi Alonso vd Westen, Fabian Wahle, Kees Grootkarzijn, Peter Sallé, Arend Jan van CalcarArend Jan van Calcar ,,

FOM Institute for Plasma Physics RijnhuizenFOM Institute for Plasma Physics Rijnhuizen

Nieuwegein, The NetherlandsNieuwegein, The Netherlands

bijkerk@rijnhuizen.nlbijkerk@rijnhuizen.nl

2

FOMFOMEUV lithography reqts on optics substratesEUV lithography reqts on optics substrates

1.4

86

m

Reticle-stage

wafer stage

SPF

GratingCollector

Wafer level

FF

PF

G

N1

N2Collector-

Source-Unit

Illuminator-

Unit

Stop

1m

Design example

European EUVL Process

Development tool

3

FOMFOMEUV imaging diagnosticsEUV imaging diagnostics

EUV telescope to measure narrow-band

size of EUV sources

EUV telescope images can differ

considerably from results pinhole imaging•EUV imaging: >40% smaller source size

•Up to 20% EUV energy in source tail

364 ±11 m FWHM

98

510 ±28 m FWHM

102

Broad band EUV pinhole image

In-band EUV ML

telescope image 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 500 1000 1500 2000

length (μm)

norm

alis

ed in

tensi

ty

In-band

Broad-band

Philips EUV Xe source

4

FOMFOM

Principle

• Bi-layer systems: reflecting & spacer layers

• Summation of in-phase partial reflections

Design/simulation/analysis

• Bragg condition: n = 2d sin (1- sin2c /sin2 )1/2

• Fresnel equations + roughness models

• DW-factor: R = R0 exp (-k (sin . )2 / )

• -ratio: dreflecting / (dreflecting + dspacer)

• Complex indices of refraction, atomic scattering factors f1, f2, density

Deposition processes

• Optimize combination materials + optical properties

• Thin film materials growth process

• Controlled low interface roughness & intermixing of layers

• Regular, reproducible stack without layer thickness errors

Multilayer reflectionMultilayer reflection

incident XUV radiation

= 0,1 - 30 nm

reflecting material

spacer

d-spacing

•Bragg: n = 2d sin (1- sin2c /sin2 )1/2

5

FOMFOMMultilayer ReqtsMultilayer Reqts

- Near-theoretical values of reflectivity

-13.5 nm @ normal incidence

- Lateral uniformity within 0.1%

-Gradients and flat profiles over 500 mm dia

- Unprecedented temporal/thermal stability

- Extreme radiation hardness: 3x104 h to R/R 1%

-Moderate vacuum conditions

- Contamination: 1% over 3x104 h

ref Louis et al, Microelectr. Engin. 27 (1995) 235-238

theoretical maximum

measured 64%

(40 layer pairs)

12 12.5 13 13.5 14 14.5 15

Status <1998

0

10

20

30

40

50

60

70

Progress in coating research twice higher

total throughput of ten-mirror EUVL system

70.15% @ 13.5 nm

70.5% @ 13.3 nm

Wavelength, nm

6

FOMFOMControl of lateral uniformityControl of lateral uniformity

- Total coating stack non

correctable thickness error 15

pm rms, or 0.2 pm per period• Factor 7 within spec

• Limited by resol. reflectometer

• 3x better then competition

‘pm lateral coating accuracy’

Louis, Zoethout, van de Kruijs, et al, 3d Int EUVL Symp., www.sematech.org/docubase (2004)

7

FOMFOM‘‘Picometer coating accuracyPicometer coating accuracy’’

Cover The Netherlands by 0.5 m of asphalt,

with a reqd accuracy of the thickness of 7 sheets of letter paper

> achieved an accuracy of the thickness of a single sheet …

on a macroscopic scale:

8

FOMFOMScaling coating technologyScaling coating technology

largest EUVL optical element

Reqt. reflectivity @ used AOI +/-< 1% of target value

0.3% d-spacing budget

Largest EUV ML optic to date successfully coated First real EUV optic from new large area EUV coating facility @ SMT

Several new coating technologies successfully incorporated

Lateral uniformity < 0.2%

Reflectivity 64.5% and uniform uniformity +/- 0.25%

9

FOMFOM

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

12.75 13.00 13.25 13.50 13.75 14.00 14.25

[nm]

Re

fle

cta

nc

e

[%]

High R

ASL+High R

Compensating ML-induced stressCompensating ML-induced stress

ASL + HR multilayer:

R=69.1 ± 0.1 %

=13.50 ± 0.003 nm

Sf= -33 ± 3 MPa

• Full stress compensation feasible without sacrificing EUV optical performance-33 MPa demonstrated

>69% reflectance

High reflectance

multilayer

Stress

compensating

multilayer

Substrate

50 periods with

small Mo fraction

30 periods with large

Mo fraction

Compounded multilayer system

Zoethout et al, SPIE 5037, Sta Clara, pp. 872-877 (2003)

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FOMFOMEUV optics key research & developmentEUV optics key research & development

Physics & engineering for 2nd generation of EUV multilayers surface photo-chemistry at EUV photon energies

chemical and diffusion barriers & interaction with incident radiation

plasma processing and deposition processes

capping layer

Mo

Si

Mo

diffusion barrier

H-O-H

h EUV

O

H

oxidation

h EUV

H

C C

H

C-growth

h EUV

T

diffusion

While meeting Zeiss-ASML road map ...

11

FOMFOM

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

100 200 300 400 500 600

Temperature (C)

Multila

yer

period c

hange (

nm

)

Barrier layers

reduce diffusion,

postpone phase-

transformation

Introduce

barrier layers

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

100 200 300 400 500 600

Temperature (C)

Multila

yer

period c

hange (

nm

)Diffusion barrier layersDiffusion barrier layers

13.5 nm multilayers for

exposure to kW EUV

plasma light sources

12

FOMFOM

-18.5

-18

-17.5

-17

1.3 1.5 2.3 2.5

logD

[cm

2/s

]

No barrier layersC barriers

1.7 1.9 2.1

1000/T (K-1)

Ea=0.3eV, D0=2.1 10-16 cm2/s

Ea=0.3eV, D0=1 10-16 cm2/s

-20

-19.5

-19

Si MoxSiy

MoxSiyMo

L.G.A.M. Alink, R.W.E. van de Kruijs, E. Louis et al., Thin Solid Films (accepted)

I. Nedelcu, R.W.E. van de Kruijs, E. Zoethout et al., (accepted).

Si

C

CMo

-First stage : C-barrier results in reduced growth of 1 monolayer

No change in activation energy

-Second stage : C-barrier results in delayed full interdiffusion of the multilayer

Tdelay = 25ºC

Barrier layers: diffusion reductionBarrier layers: diffusion reduction

D=D0exp(-Ea/kT)

Arrhenius:

13

FOMFOM

0

5

10

15

20

25

20 40 60 80 100 120 140

= 0.4

(110)

(200)

(211)

(220)(310)

(222)

(321)

Experimental data :

Calculated polycrystalline

cubic Mo diffraction spectrum

(random orientations)

Absolute intensities :

Diffracting volumes

Peak widths :

Crystallite sizes, strain fields

Peak positions :

Lattice structure,

lattice strain

Relative intensities :

Crystallite orientations

Diffraction angle 2 (degrees)

Diffracted

intensity (cps)

WAXRD

Nano-crystallite growthNano-crystallite growth

cos

940

W

.L =Scherrer’s equation:

: x-ray wavelength.

,W : diffraction angle and width.

14

FOMFOM

30

35

40

45

50

55

0 10 20 30 40 50 60 70 80

Lattice angle (degrees)

Cry

sta

llit

e s

ize (

Am

gstr

om

)

30

35

40

45

50

55

0 10 20 30 40 50 60 70 80

Lattice angle (degrees)

Cry

sta

llit

e s

ize (

Am

gstr

om

)

Nano-crystallite growthNano-crystallite growth

30

35

40

45

50

55

0 10 20 30 40 50 60 70 80

Lattice angle (degrees)

Cry

sta

llit

e s

ize (

Am

gstr

om

)

lattice angle (degrees)

L

L

increases

d increasesdMo increases.

dMo

dMo

Columnar crystallite growth.

Transversal size determined by Mo layer thickness.

Mo nucleates on silicide layer:

structure of the silicide determines

structure of Mo

15

FOMFOMProtective capping layersProtective capping layers

13 nm

Spacer (Si)

Reflector (Mo)

Exposure of multilayer to high EUV flux

P = 10 mW/mm2

At (U)HV background gases

H2O ~ 10-6 mbar

CxHy < 10-10 mbar

Cap layer

Stable C capping layer provides effective

protection

Constant reflectivity over 15 hr continued

exposure

C properties critically depend on deposition & EUV

stabilization

0

2

4

6

8

10

0 2 4 6 8 10 12 14 16

Exposure time (hours)

Reflection loss (

%) uncapped

Mo/Si

standard C

stabilized C

Oestreich, Louis, et al; SPIE 4146-07, 2000

Yakshin, Bijkerk,et al, Aset/Sematech Proc. www.sematech.org/docubase, pp. P6-6 (2001)

16

FOMFOMProtective capping layers, C depositionProtective capping layers, C deposition

Without EUV: physisorption of CH at mirror surface

EUV: cracking of molecular bonds, chemisorption

Lifetime criterion: 1 nm C (~1% abs)

C-contamination model Jonkers and Bisschops

S. Oestreich et al; SPIE 4146-07, 2000

17

FOMFOMControl of surface oxidationControl of surface oxidation

Life time expt: 230 h EUV exposure @ PTB

-3.0

-2.0

-1.0

0.0

1.0

2.0

-6.5

-6.0

-5.5

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

X

Y

66.4 %

66.2 %

66.0 %

65.8 %

65.6 %

65.4 %

65.2 %

65.0 %

estimated position of EUV spot

65.7%

66.4%

Initial reflectance 66.4%Background: CxHy, H2O, O2

Intensities: 30 mW/mm

• No loss of reflectivity

• Surface analysis shows

no oxidation or other damage

• Extrapolation: 1000 hrs lifetime(1% R)

Mo/Si + capping layer:

18

FOMFOMCoating infrastructureCoating infrastructure

Advanced Development Coater

• thermal, medium energy deposition

• plasma & ion surface treatment

Analysis Advanced Development Coater

• XPS, AES, SEM

• Ion-beam surface analysis

• GI- XRR, XRD

substrate

Kaufmann ion source

RF plasma source

thermal energy deposition

magnetrons

in-situ reflectivity

19

FOMFOMSummary & outlookSummary & outlook

1. Existing ML know-how available to VUV/XFEL ML applications

• Bi-layer systems with high, inherent thermal stability

• Barrier layered systems with enhanced reflectivity + thermal stability

• Capped systems with stabilized surfaces

• Technology to uniformly coat large, GI optical surfaces

2. Synergy from running, lithography motivated research programmes

• Inert MLs with high radiation hardness

• High thermal stability

• Studies on atomic/molecular deposition processes

3. ML-VUV/XFEL case?

• Thermal issue by average power on ML ‘managable’

• Peak power levels show physics materials limits, but not likely ML specific

• Deposition & layer hardening process essential

Opportunity for exploring the ML VUV/XFEL limit