DIFFER is part of and

Multilayer-based solutions for suppression of IR radiation in EUV systems

EUVL Symposium, Brussels, Belgium, October 2012

V.V. Medvedev1, A.E. Yakshin1, E. Louis1, R.W.E. van de Kruijs1, A.J.R. van den Boogaard1, F.A. van Goor2, V.M. Krivtsun3, A.M. Yakunin4, F. Bijkerk1,2

1 FOM Institute DIFFER, Nieuwegein, The Netherlands

2 MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands

3 Institute for Spectroscopy RAS, Troitsk, Russia

4 ASML, Veldhoven, The Netherlands

2

Outline

o Parasitic IR radiation

o IR antireflective filtering + EUV reflection

o IR diffractive deflection + EUV reflection

o Summary

3

Laser-produced plasma (LPP) EUV source

!!! A lot of scattered laser IR radiation

Mo/Si optics

Reflected CO2 laser radiation propagates

along with EUV

Heat loads on projection optics

Heat loads on wafer stage

4

IR antireflecting multilayer mirrors

IR+EUV EUV

IR suppression + EUV reflection

Mo/Si multilayer is opaque for IR radiation

IR transparent materials should be used

5

IR-transparent design

Philips Research Opt. Lett. 34, pg. 3680 (2009)

Full multilayer design:

Disadvantages:

o Complicated multilayer design

o Insufficient IR suppression (23x)

o Thick AR layers -> increased rougnhess

Rmin=4.4%

EUV

IR

6

Classical quarter-wavelength antireflection

h = l/4nC

R1

R2

IR

R1=R2 requires perfect matching of refractive indices nC=(nS)1/2

Limited choice of materials for substrate

nC

nS

IR EUV

7

Smart antireflective filtering

d1 nC

nS

metal d2

R1

R2

IR IR EUV

R2 = f(d2)

R1=R2 can be achieve by adjusting d2 for an arbitrary substrate

8

EUV mirror + thin metal film AR coating

10 nm Mo layer

Si substrate

100xB4C/Si multilayer

Opt. Lett. 37, pg. 1169 (2012)

Magnetron deposited test coating

13.2 13.4 13.6 13.80.0

0.1

0.2

0.3

0.4

0.5

EU

V R

efl

ec

tan

ce

Wavelength, nm

6 8 10 12 140.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

IR R

efl

ec

tan

ce

Wavelength, m

45% EUV peak reflectance

IR suppression 250x

9

Grating-based spectral purity filter

10

IR phase-shift suppression

p/2 p/2

RA

RB

zero order: R(0) = 0

l/4

Out-of-phase interference for specular reflection

Reflected radiation is distributed between off-specular diffraction orders

= 10.6 m – CO2 laser wavelength

h = l/4 = 2.65 m – groove depth

Calculated R(0) for square metal

grating h=l/4

2 4 6 8 10 12 1410

-3

10-2

10-1

100

0th-o

rde

r re

fle

ctio

n, R

(0)

p/l

11

Test structures

50 m

Masked deposition of Si grating

Mo/Si multilayer deposition on top

of Si grating

Test structures:

p = 100 m

→ Diffraction angle at 10.6 m q ≈ 6°

H = 2.35 m ± 0.05 m (AFM measured)

→ Reflectance minimum at l ≈ 9.4 m

AFM profile

Opt. Lett. 37, 160 (2012)

12

EUV Reflectance

61% EUV peak reflectance

Losses due to structure imperfections

Test IR-PsR structure, SEM top view

IR suppression 70x

5 10 15 200.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

IR R

efl

ec

tan

ce

Wavelength, m

13.0 13.2 13.4 13.6 13.8 14.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

EU

V R

efl

ec

tan

ce

Wavelength, nm

IR-PsR

Reference

10 m

13

Summary

Simple design of IR AR coating for B4C/Si based EUV multilayer

was proposed

test coatings were deposited using magnetron sputtering

250x IR suppression achieved

45% of EUV peak reflectance achieved

Design of grating-based IR SPF was proposed

test structures were manufactured using masked deposition

61% of EUV peak reflectance achieved

70x IR suppression achieved

14

Acknowledgements

Coworkers at , , , and

Foundation from and EXEPT program