Contamination Removal of EUVL masks and optics using

13.5-nm and 172-nm radiation

Takeo Watanabe, Kazuhiro Takeo Watanabe, Kazuhiro HamamotoHamamoto and and HirooHiroo KinoshitaKinoshita

University of HyogoUniversity of Hyogo

IEUVI Resist & Contamination TWG Oct.19, 2006 in Barcelona

Method of contamination removal

(1) Cleaning of EUVL imaging optics(The optics used for EUVL has been aligned

in high accuracy. So the cleaning of imaging opticsrequires in-situ process.)

⇒ In-situ contamination removal by synchrotron radiation without heating

(2) Cleaning of EUVL masks(Both large cleaning area and high speed are required.)

⇒ Contamination removal by 172-nm-wavelength.

Evaluation between before and after removal・Contamination thickness → Optical thickness measuring system・Surface roughness → AFM・Reflectivity → Reflectometer (NewSUBARU BL-10)

Online contamination removalby a wavelength of 13.5 nm

20 40 60 80 10010-8

10-7

10-6

10-5

10-4

10-3

Parti

al p

ress

ure

(Pa)

Mass number

H2O

CO2CxHy

N2

Partial pressure in ETS-1

Total pressure: 1×10-5 Pa

Contamination adhesion in ETS-1 exposure system

Sample of the multilayer isset on the mask stage, andEUV is irradiated.

M2M1 M3

Wafer

Mask

Deposition rate: 7.5 nm/hr (0.125 nm/min)

Thickness of contamination

Electron beam current: 200 mA

0 100 200 300 400 5000

10

20

30

40

50

60

70Th

ickn

ess

of c

onta

min

atio

n (n

m)

Irradiation time (min.)

Reflectivity of multilayer

Multilayer reflectivity of 10% decreasedby 4 hours irradiation

0 100 200 300 400 5000.3

0.4

0.5

0.6

0.7R

efle

ctiv

ity

Irradiation time (min.)

Surface roughness of multilayer

0 100 200 300 400 5000.10

0.15

0.20

0.25

0.30

0.35

0.40S

urfa

ce ro

ughn

ess

(nm

)

Irradiation time (min.)

C

O

Ta

Pho

toel

ectro

n in

tens

ity fo

r C

, O, S

i (cp

s. e

V) Photoelectron intensity for

Ta (cps. eV)

Sputtering time (min.)

AES spectrum of contamination of mask

The ratio of C to O is 96:4

Experimental setup of SR cleaning

Contaminationtesting chamber

Storagering

M1 mirror

M2 mirrorM3 mirror(Branch)

ETS-1

adding O2 during

SR irradiation

Back pressure:5.0×10-5 Pa

pressure:5.0×10-2 Pa

Incident angle

TMP

Photodiode (GaAsP)

SR

10°

Mask sampleOxygen

Experimental results

0.85

0.9

0.95

1

1.05

1.1

1.15

0 10 20 30 40 50 60

Time (min.)

Normalized reflectivity

Normalized storage ring current Pressure: 5.0×10-2 Pa

Electron beam current: 130 mA

Irradiation: 7 hr

Before cleaning After cleaning

Contamination of 0.1-µm-thick was removed.

0 1x106 2x106 3x106 4x106 5x106 6x106 7x106 8x1060

20

40

60

80

100

120

140

160

180

200

Red

uctio

n in

thic

knes

s (n

m)

Exposure dose (mAs)

Reduction of contamination thickness

Removal rate:0.24 nm/min

7 hr

Electron beam current: 130 mA

Before cleaning

A

D

BC

E

Reflectivity of multilayer (measurement: NS-BL10)

After cleaning

0

0.2

0.4

0.6

12.0 13.0 14.0 15.0

Wavelength (nm)

Ref

lect

ivity ED

CB

A0

0.2

0.4

0.6

12.0 13.0 14.0 15.0

Wavelength (nm)

Ref

lect

ivity

absorber absorber

multilayermultilayer

contamination absorber

Offline contamination removalby a wavelength of 172 nm

Mask cleaning using 172 nm-excimer VUV/O3

⇒ A high density active oxygen species can be generated.

The absorption coefficient to the oxygen molecule at the wavelengthof 172 nm is 20 times larger than that at the wavelength of 185 nm of the low-pressure mercury lamp.

172 nmCOx， H2，CHz，H2O，…

oxygen(O2)

CxHy

Mo/Si

ozone(O3)

Active oxygen species(O*)

contamination

Experimental setup of 172 nm cleaning

Intensity 20 mW/cm2Distance 1 mmSample size 8-inchTemperature 25℃Environment in the air / in O2-rich vacuum

Stage

1mm

172 nm excimer lamp

O2-rich vacuum environment:The initial back pressure of the chamber was 500 Pa by scroll pump, and an O2 flow kept the pressure at 2×103 Pa.

0 10 20 30 400

5

10

15

20

25

30R

emov

al th

ickn

ess

(nm

)

Cleaning time (min)

Results of mask cleaning using 172 nm-excimer lamp(1) Reduction of contamination thickness

in vacuumrate: 2 nm/min.

in the airrate: 0.53 nm/min.

Results of mask cleaning using 172 nm-excimer lamp(2) Reflectivity of multilayer

0%

10%

20%

30%

40%

50%

60%

70%

12.0 12.5 13.0 13.5 14.0 14.5 15.0Wavelength (nm)

Ref

lect

ivity Before cleaning

After cleaning

Summary

(1) From the result of AES, it has been understood that the element of contamination is almost carbon.

(2) The effectiveness of the contamination removal for EUVL imaging optics using both in-situ and non-heating method by EUV irradiation in the oxygen atmosphere is confirmed.

(3) The effectiveness of the contamination removal for the finished EUVL mask in off-line process using the 172 nm-excimer lamp in the O2-rich vacuum atmosphere at the room temperature is confirmed.

Thank you for your attention!!

Outgassing Measurementin University of Hyogo

-Short summary-

Takeo Watanabe, Hiroo KinoshitaUniversity of Hyogo

IEUVI Resist & Contamination TWG Oct.19, 2006 in Barcelona

Sample

PC controlled fast speed shutter(∆∆∆∆t=11 ms)Mo/Si MLs

Concave Mirror

High-sensitive ion counting typeQ-massspectrometer

Mo/Si MLs Two Plane Mirrors

SR

Setup of novel resist evaluation system

Simulating six-mirror optics

Practical exposure spectrum

1) Measurements of sensitivity2) Outgas characteristics3) Chemical reaction analysis

Distance 30 mm

Model HAL/3F/PIC 501 RC, Hiden Analytical, Ltd.

Setup of novel resist evaluation system

Loadlock chamberTMP 300L/s

Sample

Shutterchamber

SR

Sample chamberTMP 300L/s

Sample insertion rod

Gate valve

Gate valve

Gate valve

Mirror chamberTMP 700L/s

Differential pumping

6.7×1016

35-200 amu4.5×1013

35-200 amu9.4×1014

35-200 amu

2.9×10173.4×1014

0.27 mW/cm2

1-200 amu

7.1×1015SynchrotronOnline QMS

Univ. of Hyogo

3.1×101635-200 amuExcluding 44 amu

2.1×101335-200 amuExcluding 44 amu

4.3×101435-200 amuExcluding 44 amu

8.3×10155×1013

1 mW/cm2

??-??? amu

2.8×1014Stand-alonesourceOnline QMS

BOC Edwards

5.7×10154.5×1012

0.13 mW/cm2

1-200 amu

1.9×1014SynchrotronOnline QMS

ASET

1.1×10152.6×1012

0.37 mW/cm2

35-435 amu

3.9×1013SynchrotronGC/MS

SEMATECH

1.3×10137.3×109

0.09 mW/cm24.37×1011Synchrotron

GC/MSIntel

Molecules/cm2/s@each intensity condition

Molecules/cm2

@5.6 mJ/cm2 dose

Estimate RateMolecules/cm2/s@Prod. Tool(0.4 W/cm2)

ResultsMethodInstitute

By Takeo Watanabe, Univ. of Hyogo 2006 Oct 19