High-radiance LDP source · Title: 2015 Source Workshop Ushio Author: [email protected] Created Date: 11/9/2015 10:32:51 PM

© Copyright 2015 Ushio Group. All Rights Reserved. 1

Yusuke Teramoto, Bárbara Santos, Guido Mertens, Ralf Kops,

Margarete Kops, Hironobu Yabuta, Akihisa Nagano, Noritaka

Ashizawa, Takahiro Shirai, Kunihiko Kasama

Ushio Inc. / BLV Licht- und Vakuumtechnik GmbH

Alexander von Wezyk, Klaus Bergmann

Fraunhofer ILT

High-radiance LDP source:

clean, stable and reliable EUV source for

mask inspection

© Copyright 2015 Ushio Group. All Rights Reserved. 2015 International Workshop on EUV and Soft X-Ray Sources, Dublin, Ireland, November 10, 2015 2

Basic principle and characteristics

Key performances

Cleanliness

Stability and reliability

Summary

O U T L I N E


Laser-assisted Discharge-produced Plasma

Liquid Tin Bath

(circulated)

Capacitor

Tin Film

Cooling

Laser

EUV

Tin Supply Disc

Tin Supply Disc

Current

• High brightness

• Appropriate plasma size (broad profile)

• Stable: no spatial and timing synchronization needed

• Reliable: 24/7 operation

• Clean: powerful debris shield


Emission spectrum: similar to CO2 laser-driven LPP

0

0.2

0.4

0.6

0.8

1

1.2

11 12 13 14 15 16 17 18 19 20 21

Inte

nsit

y

Wavelength (nm)

Measured behind debris shield, not spatially resolved.

𝐼 𝜆 𝑑𝜆13.635 𝑛𝑚

13.365 𝑛𝑚

𝐼 𝜆 𝑑𝜆21 𝑛𝑚

10 𝑛𝑚

× 100 = 12.6 %

Similar spectrum to Sn-LPP

Beneficial in inspection and other applications


Plasma shape: litho vs inspection

Plasma for mask inspection source

L: ~450 mm

D: ~200 mm

Low~medium pulse energy

1 mm

Plasma for lithography beta source

L: ~500 mm

D: ~230 mm

High pulse energy

XTREME technologies


High radiance, appropriate plasma size

Diameter: 200 mm (FWHM)

Length: 450 mm (FWHM)

10 kHz, continuous operation

Very high peak radiance at

plasma

Plasma size smaller than DPP,

larger than LPP: good spatial

stability


Radiance vs diameter (etendue)

0

10

20

30

40

50

60

70

0.0E+00 5.0E-03 1.0E-02 1.5E-02

Rad

ian

ce (

W/m

m2/s

r)

Etendue (mm2sr)

s=3.0 %

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5

Rela

tiv

e r

ad

ian

ce

Time (minute)

s=3.1 %

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5

Rela

tiv

e r

ad

ian

ce

Time (minute)

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5

Rela

tiv

e r

ad

ian

ce

Time (minute)

s=3.4 %


Stable timing and no misfire

No missing pulse.

No misfire.

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

0 200 400 600 800 1000

Vo

ltag

e (

kV

)

Time (ms)

Frequency is constant.

Defined by laser pulse.


Radiance at plasma: 140 W/mm2/sr

0

20

40

60

80

100

120

140

160

0 2000 4000 6000 8000 10000

Rad

ian

ce (

W/m

m2/s

r)

Pulse repetition rate (Hz)

Averaged radiance in f200 mm

Peak radiance: 180 W/mm2/sr

Area-averaged radiance: 140 W/mm2/sr

15 kW (10 kHz)


Mechanical debris shield concept

Laser Ions Neutrals

Debris shield

Clean EUV

Neutrals (Macro/microscopic particles and vapor)

- Completely stopped by debris shield

Charged particles (fast ions)

- Mostly stopped by debris shield

- Slow down in debris shield

Liquid Sn


Cleanliness evaluation

Buffer gas

500 mm

Debris shield

Ru mirror sample

Plasma

Frequency

Discharge frequency: 5, 7 and 9 kHz

Buffer gas: Variable

Sample: 8-nm-thick Ru on Si

Source-sample distance: 500 mm

Incidence angle: 90˚, 15˚

Analysis: XRF

After 100~500M pulse


Cleanliness: influence of frequency

0

5

10

5 kHz 7 kHz 9 kHz

Ru sputter rate (nm/Bpulse)

0

0.5

1

5 kHz 7 kHz 9 kHz

Sn deposition (nm)

• There is erosion due to

ions passing through the

debris shield.

• There is a weak

relationship between

sputter rate and

frequency.

• There is a slight

deposition of Sn.

• However, according to the

experiments done so far,

it does not grow and

stops around at


Cleanliness: influence of number of pulses

0

0.1

0.2

0 50 100 150 200 250 300

Rela

tive

thic

kn

ess (

nm

)

Accumulated pulse (Mpulse)

Sn

-2

-1.5

-1

-0.5

0

0 50 100 150 200 250 300

Rela

tive

thic

kn

ess (

nm

)

Accumulated pulse (Mpulse)

Ru

Grazing incidence

Sn layer does not grow in proportion to

the number of pulses.

Ru is sputtered at constant rate.

Further reduction is under development.


Radiance behind debris shield: 120 W/mm2/sr

Measured behind debris shield as clean EUV photon

Peak radiance: 145 W/mm2/sr

Area-averaged radiance: 120 W/mm2/sr

0

20

40

60

80

100

120

140

0 2000 4000 6000 8000 10000

Rad

ian

ce (

W/m

m2/s

r)

Pulse repetition rate (Hz)

Averaged radiance in f200 mm

This is what the

industry wants.

This is the

need.

20 % brighter than wanted


Energy stability:


Position stability: ~6 mm

-30

-20

-10

0

10

20

30

0 1 2 3 4 5

Dis

pla

cem

en

t (m

m)

Time (minute)

Measured with camera placed on optical axis

Exposure time: 5 ms

Standard deviation: 6.0~6.4 mm


Reliability: tests ongoing

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120

Rad

ian

ce (

W/m

m2/s

r)

Time (hour)

Nov2013 R&D Source

Oct2014 R&D Source

Feb2015 R&D Source

Sep2015 Prototype

The prototype machine is dedicated to days-long non-interrupted

operation test.

Several 5-day operations were carried out.

Output radiance will be increased by (1) increasing operation frequency

and (2) parameter optimization, and stabilized by (3) applying

stabilization control.

System adjustments


Prototype LDP machine


Summary

R&D source Energy stability and position stability have been

improved.

Sample exposure experiments are being performed.

Improved version of the debris shield has been

designed and will be tested early 2016.

It has an improved gas distribution leading to

better mitigation performance.

Prototype source 5-day non-interrupted operations have been carried

out several times.

Successful 5-day-long non-stop operations.

Aiming at system/module reliability improvement.

Stabilization control will be implemented.


Performance summary

Item Performance Remark

Pulse repetition frequency up to 10 kHz variable

Duty cycle 100 %

Input power up to 15 kW variable

In-band EUV power up to 300 W/2psr at plasma

Radiance 120 W/mm2/sr*

* value measured behind debris shield

9 kHz

200-mm area averaged

Plasma size 200×450 mm FWHM typical value

Energy stability

Pulse: ~10 %

Dose: 0.1**~3 %

** with feedback control

Radiance stability 5.8 %***

***from 1.5-ms-exposure observation

10 kHz

Position stability 6~10 mm

Documents

High-radiance LDP source · Title: 2015 Source Workshop Ushio Author: [email protected] Created Date: 11/9/2015 10:32:51 PM