mitigation and selection of ion and particulate emission...

Mitigation and selection of ion and particulate

emission from Laser-produced plasmas used

for Extreme UltraViolet Lithography

Paolo Di Lazzaro

Co-authors: Sarah Bollanti, Francesco Flora, Luca Mezi, Daniele Murra, Amalia Torre

ENEA Frascati Research Centre, Dept. Applications of Radiation, P.O. Box 65, 00044 Frascati (Rome, Italy)

✉ [email protected]

• Motivation

• Measurement of debris characteristics

• Thermalization and suppression of debris

• Conclusion

OUTLINE

COST MP0601 Joint event Paris 17 November 2011 P. Di Lazzaro

XeCl excimer lasers as plasma-driver

LPX-305, PBUR 0.5 J, 25 ns, 50 Hz

Oscillator

HERCULES

PBUR

5 J, 120 ns, 5 Hz

Oscillator or Amplifier


The ENEA laser-driven plasma source


Convex

mirror

Flat

mirror

Mask

F1

Ellipsoidal

collector

mirror

IF Plasma

source

Zr

filter

=2’’

Quartz

window

XeCl

laser

Gate

valve

Bypass

valve

DMS

Focusing

lens

Ellipsoidal

mirror

Schwarzschild

Objective

M~10

Wafer/

/LiF

Vibration isolated, temperature

controlled Invar board

Flexible

duct

10 cm

Source chamber

Projection chamber

Kr: 1 mbar

Vacuum: 10-6 mbar

5-axes high-precision

remote-control stages

convex mirror ellipsoidal mirrors plasma source

mask stage Schwarzschild wafer stage laser beam focusing lens

EGERIA: the first Italian MET for EUVL


Line space printing on PMMA: 90 nm resolution

0 500 1000 1500 2000 2500 3000 3500 4000

90 nm

Hei

ght

[nm

]

5

15

20

0

Horizontal position [nm]

10

2 m

2-D pattern of

160-nm and 110-

nm lines (left)

observed by

atomic force

microscope.

Line profile

integrated on the

dashed region.

90-nm edge

response!

European Physics Letters 84, 58003 p1 (2008)

Particulate debris

0.5 ms after laser pulse

Visible light emission

from atomic debris

Glass plate put 5-

cm from plasma in

vacuum, after 104

pulses

screened

Laser-plasmas emit debris, too

Distance from source (cm)


• Motivation

Measurement of debris characteristics


• Conclusion

OUTLINE


CCD Detection of ions debris

2 µs after laser shot

3 µs

Laser: 5 J - 120 ns

Wheels for tape

Triplet lens

CCD

5 cm

Ta tape target

Plasma

38 cm above the plasma

14 cm

18 cm

4 µs

particle

debris


Velocity of ions emitted by Laser-plasmas

Laser: 5 J - 120 ns 5.1012 W/cm2

Lens

Ta tape

target

Plasma

Faraday cup

1 m

10 20 30 40 Time from plasma gen. (µs)

0

10

20

Ions

curr

ent

(mA

/cm

2)

25 30 40 50 100 70 V (km/s)

10 5 2 1 0.6 Ek (keV)

3.10

20

6.10

20

0

Ions/

sr/s

Vmax= 83 km/s

Vmin= 26 km/s

For Z = 2, ions flux 2 1020 ions/sr/s in 15 s. 3 1015 ions/sr

Rev. Sci. Instrum. 71, 1405 (2000)


Turning glass to measure the cluster-droplets

debris velocity

Debris with different velocities hit the rotating glass behind the slit in different times,

leaving a “coma”-shaped trace on the glass. Each point of trace corresponds to a

given velocity.

Cu tape

rotating disk

LASER

Spinning motor

(1800 rpm) Screen in front of

rotating disk

LASER

2-mm SLIT


0

500

1000

1500

2000

2500

3000

0 200 400 600 800 1000 1200

Velocity (m/s)

De

bri

s /m

m²

Droplets debris velocity measured in 9 mbar*cm Kr

Debris on glass are framed at the optical microscope, and then identified

and computed by a dedicated software. Most debris sizes are sub- m.


A pendulum to measure the momentum of debris

Cu tape

target

XeCl

laser (4 J

120 ns)

Shock

wave

Pendulum:

2 g

35x50 mm2

1 sr

intercepted

PD

He-Ne

36 mm

10 4

10 3

0.01 0.1 1 10 100 10 3

0

20

40

60

Air pressure (mbar)

pen

du

lum

sp

eed

(m

m/s

) I=1012

W/cm2

I=1010

W/cm2

When P > 0,1 mbar the speed of pendulum is due to debris + shock wave.

When P < 0,1 mbar the speed of pendulum is independent of pressure, and it is

only caused by debris. The measured momentum is 2 10-5 Kg m/s in 1 sr.


• Motivation



• Conclusion

OUTLINE


VACUUM KRYPTON ARGON

Gas mitigation, after 104 shots Cu target (red!)

Dashed zone Dashed zone Dashed zone


10-4 10-3 0.01 0.1 1 1 0

0.01

0.1

1

10

100

Debris diameter Φ [ m

Max

imu

m d

ebri

s sp

eed

[km

/s]

V -0.7

Atomic Droplets

Faraday-cup measurement

Turning glass plates measurements

Clusters

RoF 0.3

Lindhard’s formula

Kr @ 1 mbar

Ar @ 0.4 mbar

1

10

100

1000

0.1

Ran

ge o

f Fl

igh

t R

oF

[cm

]

The buffer gas stops the smaller and faster debris

Europhysics Letters

56, 676 (2001).


Our DMS, reduced to practice…

Two patents: EP 1211918 A1 and UIBM 0001372004

Plasma

Magnet

Filter

Fan, commercial

Glass plate

2.7 cm

4 cm 6.2 cm 8 cm

Mylar screen


DMS frame definition

Y Gas Filter

Focusing lens Cu tape target Magnet pole

Turning direction

Glass plate during exposition

Target normal 5 blades fan

The debris cutting speed, that is

the maximum debris speed for

which debris are stopped by the

blade, varies with the vertical

position (Y) along the plate. Since

the fan was operated at 6000

r.p.m., rotating upwards, the

cutting speed turns out to range

from a minimum of 90 m/s at Y =

20 mm to a maximum of 500 m/s

at Y = -25 mm.


Measurement of debris mitigation factors

Atomic debris mitigation factor (DMf)

At Y = -25 mm …... DMf = 800

Droplets mitigation factor

Using Kr DMf = 1600

Using Ar DMf = 1200

Microscope analysis for

droplets

Densitometry analysis for

atoms and clusters:

Target Normal

-40 -20 0 20 40 Y [mm]

10 mbar.cm Kr + fan + magnet

(0.3 T) (50.000 shots)

4 mbar.cm Ar

+ fan (50.000 shots)

Vacuum + fan (3000 shots)

Vacuum (3.000 shots)

10 mbar.cm Kr

+ fan (50.000 shots)

Applied Physics B 76, 277 (2003) ; Applied Physics B 96, 479 (2009)

L

D RPM

R

60

2 RPMR

D

LVmA

A new proposal: a fan to select the velocity

of emitted particles (cluster and droplets)

Flying particle

VmA is the minimum velocity of a particle to pass through the fan.

Then, VmA is the maximum velocity of debris stopped by the fan.


Possible schemes of the new fans

Ufficio Italiano Brevetti e Marchi n. 0001372004 22 Marzo 2010


• Motivation



• Conclusion

OUTLINE


Ut breviter dicam

• We have used a “dirty” Laser-plasma source to measure the

characteristics of ion, cluster and particulate debris.

• According with the measured velocity ranges, spatial distribution

and energy spectrum of each kind of debris, we have designed and

tested a debris mitigation systems (DMS) able to thermalize and

suppress both ionic and particulate debris.

• The effectiveness of our DMS was estimated by different methods,

including a microscope analysis of exposed glasses performed by a

dedicated code for the image processing.

• The values of DMf obtained (~ 800 for atomic debris and ~ 1200

for debris > 0,5 m) are to our knowledge among the best achieved

ever. Further improvements are expected in the near future, when

the prototype of the high-speed-fan DMS patented by ENEA will

be tested in our Lab.


Laboratorio Laser Eccimeri, ENEA Frascati Award of Excellence ENEA for the first Italian Micro exposure

tool for EUV lithography


Selected references

S. Bollanti, et al.: “Flight range of the particulate in a laser-plasma generated soft X-ray

chamber”, Appl. Phys. A 71, 255 (2000).

K. Fournier, et al.: “Novel laser ion sources” Rev. Sci. Instrum. 71, 1405 (2000).

F. Flora, et al.: “Krypton as stopper for ions and small debris in laser-plasma sources”

Europhys. Lett. 56, 676 (2001).

S. Bollanti, et al.: “High efficiency, clean EUV plasma source at 10-30 nm, driven by a

long pulsewidth excimer laser” Appl. Phys. B 76, 277 (2003).

K. Fournier, et al.: “Analysis of high-n dielectronic Rydberg satellites in the spectra of Na-

like Zn XX and Mg-like Zn XIX", Phys. Rev. E 70, 016406, 1 (2004).

P. Di Lazzaro, F. Flora, N. Lisi, C.E. Zheng: “Discussion for plasma evolution on laser

target” ENEA Technical Report 41/FIS (2006).

S. Bollanti, P. Di Lazzaro, F. Flora, L. Mezi, D. Murra and A. Torre: “First results of high-

resolution patterning by the ENEA laboratory-scale extreme ultraviolet projection

lithography system”, European Physics Letters 84, 58003 p1 (2008).

P. Di Lazzaro, C.E. Zheng: “A note on the use of refitted photo-multiplier to measure

laser-plasma ion flow rates” ENEA Technical Report 9/FIM (2009).

S. Bollanti, P. Di Lazzaro, F. Flora, L. Mezi, D. Murra and A. Torre: “Laser-plasma-source

debris-related investigation: an aspect of the ENEA micro-exposure tool”, Appl.

Phys. B 96, 4797 (2009).

I risultati del DMS sugli specchi

• Nel caso degli specchi, la valutazione dell’efficacia del DMS è stata

fatta rapportando il calo di riflettività dello specchio esposto in vuoto

a quello dello specchio esposto con il DMS, normalizzati al numero di

colpi. I multilayer e le misure di riflettività sono stati a cura dell’INFN-

LNL e del DEI-Università di Padova.

• In tutti i casi il calo di riflettività è confrontabile con l’errore della

singola misura. Questo comporta un grande errore sul DMf.

• Ciononostante, risulta evidente una similarità con il DMf atomico: il

degrado è dovuto principalmente ad atomi e clusters.

R peak before the exposure (%)

R peak after the exposure (%)

Corresponding DMf

M2 (Vacuum , 900 shots ) 66.0 1 56.0 2.6 -

M3 (Kr + fan , 60000 shots ) 66.0 1 63.8 1.4 1000 130 300

M4 (Ar + fan , 60000 shots ) 68.3 1 66.0 1.4 820 120 290

M5 (Kr + fan + magnet , 60000 shots ) 68.3 1 65.2 1.4 260 80 220

fenditura (1 mm)

Misura della velocità del particolato tramite deposizione su vetrini rotanti

Vetrino esposto a

40.000 colpi visto

in riflessione

Vvetrino=1.1 cm / ms

1/ Vvetrino=90 µs / mm

Cu Plasma

6 cm 1 cm

Fotodiodo

per trigger

Vetrino incollato su disco rotante

Disco rotante f=20 Hz

(1200 r.p.m.)

LED

Schermo

Deposito di ioni in

corrispondenza

della fenditura

Z (mm) 2.0 1.5 1.0 0.5 0

Direzione del

moto del vetrino

Tempo ( s) 200 150 100 50 0

Velocità (Km/s) 0.3 0.5 0.8 1.4

Atomic debris mitigation:

choosing the gas, range of flight issue

• The range of flight of heavy

debris ions (Sn, Ta) is shorter

than for light target (Li), for the

same kinetic energy.

• Apparently, tin and tantalum ions

can be stopped in a range much

shorter than the path length for a

reasonable EUV transmission

(10 cm, T = 86%), both in Ar at

0.4 mbar and in Kr at 1 mbar. It

is’nt, due to momentum

transferred to gas (the dirty

cloud moves).

• Kr is 4 times better than Ar at a

fixed transmission factor.

0 0.5 1 1.5 2 2.5 3 0.1

1

10

100

Gas pressures (mbar)

Ca

lcu

laa

ted

io

n ra

ng

e of

fli

gh

t (

cm

)

In Ar gas

In Kr gas

Li ions in Ar

Sn ions in Ar

Sn ions in Kr

Ta ions in Ar

Ta ions in Kr

2 keV

Applied Physics A 71, 255 (2000).

Ion charge state measured by energy analyzer

- 2 kV

+2 kV

Laser: 2 J – 10 ns I=1013 W/cm2

Tape Target: Ta, Cu, Al

Plasma

1.8 m

0 10 20 30 40 50 600.2

0

0.2

0.4

0.6

0.8

1

AlCuTa

time (microsec)

SE

M s

igna

l (V

)

0 2 4 6 8 10 12 14 160.2

0

0.2

0.4

0.6

0.8

1

1.2

Al

CuTa

Kinetic Energy (keV)

SEM

signal

(V)

Z=2

Z=3 Z=4 Z=5

Z=6

Z=7Z=1

Z=1

Z=2 Z=3

Z=4

E/Z= 1.2 keV

Laser shot

Rev. Sci. Instrum. 71, 1405 (2000)

mitigation and selection of ion and particulate emission...

Documents