H. Solak, 16.7.09, Honolulu

EUV Interference Lithography

Harun H. Solak, V. Auzelyte, A. Langner, S. S. Sarkar, A. Weber,H. Pruchova, M. Kropf, Y. Ekinci, C. David, J. Gobrecht

Laboratory for Micro and Nanotechnology,Paul Scherrer Institute

Switzerland

H. Solak, 16.7.09, Honolulu

Outline

EUV Interference scheme

Beam for EUV-IL

Masks for EUV-IL

EUV-IL results and understanding resist behavior

Future of PSI EUV-IL tool

H. Solak, 16.7.09, Honolulu

EUV-IL at the Swiss Light Source:

a nanofabrication facility for academic and industrial useIn operation since 2003

Available to users through proposals or for a fee

EUV photoresist characterization – 300+ resists tested

Major upgrade in 2009 - focus on below 20 nm patterning

H. Solak, 16.7.09, Honolulu

EUV Interference Scheme

Line/space pattern

2-beam interference

• Frequency multiplication: Factor depending on

the diffraction orders chosen

• Good match to undulator radiation

• Achromatic (no temporal coherence needed)

• Requires spatial coherence

H. Solak, 16.7.09, Honolulu

EUV Interference Scheme4-beam interference

• Frequency multiplication

• Grating phases determine the pattern

• Profile not sinusoidal

Simulated intensity

H. Solak, 16.7.09, Honolulu

EUV beam for Interference Lithography• Spatial coherence:

• Undulator radiation

• Spatial filtering (pinhole)

• Nothing in the beam after pinhole (no optics, filters, windows etc)

• Uniform illumination

• Stable beam: SLS and beamline

• Bandwidth (interferometer dependent)

• Grating interferometer (achromatic)

H. Solak, 16.7.09, Honolulu

EUV beam for Interference Lithography

H. Solak, 16.7.09, Honolulu

Electron Beam Lithography + dry etching

Grating Masks

35 nm to 2000 nm pitches

Many pitches and patterns on one mask

100 nm (42% transmission)

10-40 nmGrating period

100 nm h/p 40 nm h/p 20 nm h/p

H. Solak, 16.7.09, Honolulu

800

• 0.8 mm lines - easy cross section – multiple period, multiple dose

• 20-50 nm h/p

• dose for EUV resist: 30-40 mJ/cm2

M390

Line/space Masks

H. Solak, 16.7.09, Honolulu

• Lines and contact holes on one mask

• 20-50 nm h/p contact holes

• 15-35 nm h/p lines

• dose for EUV resist: 40-80 mJ/cm2

M394

Contact Hole Masks1 mm

H. Solak, 16.7.09, Honolulu

High efficiency Mo Masks

100 nm

+1st order

-1st order

0th orderEUV

Grating

EUV-CCD Camera

80 85 90 95 1000

1

2

3

4

2.0 2.5 3.0 3.5 4.0

90 nm-thick Mo and 40% duty cycle grating were used for the calculated efficiency

Measured efficiency Calculated efficiency

1st /0th o

rder

rela

tive

effic

ienc

y

Undulator energy (eV)

1st order

Energy = 92.5 eV

1st order

0th order

Intensity (a.u)* M. Saidani et al, MNE 08

150 nm-pitch Mo gratingThickness: 90 nm

H. Solak, 16.7.09, Honolulu

Zero-zeroth-order PMMA grating

600 nm-pitch PMMA gratingThickness: 240 nm

1st order

0th order

Frame: EUV transmitted by membrane around square grating

H. Solak, 16.7.09, Honolulu

Line/space Patterns in PMMA

50 nm half pitch 45 nm 40 nm

35 nm 30 nm

H. Solak, 16.7.09, Honolulu

20 nm

Calixarene resist

12.5 nm

TEBN-1 from Tokuyama, Japan

H. Solak, 16.7.09, Honolulu

30 nm

Hydrogen silsesquioxane (HSQ)

20 nm

Fox-12, Dow Corning

H. Solak, 16.7.09, Honolulu

Beyond the roadmap

Resist: Fox12 (Dow Corning)Thickness: 20 nm

11 nm h/p

No FUNDAMENTAL limit down to 11 nm !

H. Solak, 16.7.09, Honolulu

50 nm h/p 42.5 nm h/p 32 nm h/p

25 nm h/p 21.5 nm h/p 19.5 nm h/p

FOX12 – HSQ - Hydrogen silsesquioxane

Testing resist performance

H. Solak, 16.7.09, Honolulu

19.9 mJ/cm2

31.0 mJ/cm2

h/p 50 nm 35 nm 30 nm 25 nm 20 nm

EUV resists

H. Solak, 16.7.09, Honolulu

EUV resists

50 nm42.5 nm

32 nm

25 nm21 nm

18 nmthinner resist

More than 300 resists were tested!

H. Solak, 16.7.09, Honolulu

Effect of substrate electrons

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

dose [mJ/cm²]

heig

ht [n

m]

Cr

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

dose [mJ/cm²]

heig

ht [n

m]

CrSi

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

dose [mJ/cm²]

heig

ht [n

m]

CrSiAuNi

Absorption length (nm)

Si 585

Cr 28

Au 21

Ni 15

H. Solak, 16.7.09, Honolulu

Contrast curves

0

10

20

30

40

50

60

70

80

0 0.5 1 1.5 2 2.5Dose (mJ)

Thic

knes

s (n

m)

after PEBafter develop

2% dose steps

H. Solak, 16.7.09, Honolulu

Resist contrast loss

0

10

20

30

40

50

60

70

200 300 400 500 600 700Dose to mask (mJ/cm2)

Line

wid

th (n

m)

HP 50HP 45HP 40

Half-pitch NILS EL/NILS50 3.14 0.8045 3.14 0.7440 3.14 0.80

EL analysis by

H. Solak, 16.7.09, Honolulu

Recent and Ongoing UpgradesFull time facility

From 15% to 100% operationDedicated undulator

Sample preparation/developmentat the beamline

WHEN:fall of 2009

NEW electron beam writer VISTEC

EBPG5000plus ES100keV

for mask preparation

H. Solak, 16.7.09, Honolulu

Sample processing:

Spin coating and development in class 100Exposures in class 1000PEB right after each exposure

– amine filtered env.

Stable flux, 10-50 mW/cm2Throughput ~ 1 wafer/hourSample stage for 4’’, 6’’, 8’’ wafersStage travel size 80×80 mm2

Software controlled exposure

EUV IL at PSI

Performance• Area: 1-4 mm2 area

• Exposure time:1-30 sec

• 11 nm … 1000 nm half-pitch