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© imec 2005 1
Microstepper vs. Interference EUV Lithography
Effects on Resist ProfilesRoel Gronheid1; Anne-Marie Goethals1;
Frieda Van Roey1; Peter Leunissen1; Harun H. Solak2; Yasin Ekinci2; Koen van Ingen Schenau3;
Cyril Vannuffel4; Amandine Jouve4
1 IMEC, Leuven, Belgium 2 Paul Scherrer Institut, Villigen, Switzerland3 ASML, Veldhoven, the Netherlands4 CEA-Leti, Grenoble, France
© imec 2005 EUVL symposium, San Diego, November 8, 2005 2
Outline
Introduction
Comparison of Resist Performance on Micro ExposureTool at LBNL and Interference Printer at PSI
‘Exposure Latitudes’ and Dose CalibrationResist ProfilesContrast Demodulation
Recent results on the interference printerChampion CAR dataPMMA results
Summary
© imec 2005 EUVL symposium, San Diego, November 8, 2005 3
IntroductionMotivation
IMEC will install an EUV full field alpha tool (0.25NA) from ASML in 2006 For installation of an early process, resist screening has been carried out using experimental EUV samples from commercial resist suppliers.Exposure tools :
Interference lithography at PSIMET at Berkeley (NA=0.3; annular illumination)
Goal of this work :To compare the performance of EUV resists on these two tools ⇒ What causes difference in resist profiles?
© imec 2005 EUVL symposium, San Diego, November 8, 2005 4
The Micro-Exposure Tool
Courtesy of Sematech/LBNL
© imec 2005 EUVL symposium, San Diego, November 8, 2005 5
The Interferometer
Diffraction Gratings2-Beam Interference
beamline Exposure chamber 800 μm
25nm
32.5nm
30nm
40nm45nm50nm
• Cleavable Dense Line/Space patterns• Dense Contact Hole arrays (with 4-Beam Interference)
© imec 2005 EUVL symposium, San Diego, November 8, 2005 6
Outline
Introduction
Comparison of Resist Performance on Micro ExposureTool at LBNL and Interference Printer at PSI
‘Exposure Latitudes’ and Dose CalibrationResist ProfilesContrast Demodulation
Recent results on the interference printerChampion CAR dataPMMA results
Summary
© imec 2005 EUVL symposium, San Diego, November 8, 2005 7
10
20
30
40
50
60
70
10 15 20 25 30Dose (mJ/cm2)
CD
(nm
)
PSI 50nmPSI 45nmPSI 40nmPSI 35nmLBNL 50nm BFLBNL 50 nm DF
CD vs Dose Performance at LBNL and PSI
For 50nm dense L/S; Using MET Bright Field
mask
Dose calibration between LBNL and PSI has been performed with various resist materials. Values at PSI were consistently 3x higher and have been corrected throughout this presentation.
Excellent agreement in CD vs. Dose performance between LBNL and PSI
EL (PSI) EL (LBNL)EUV-16 16% 13%EUV-18 15% 16%
EUV-18
© imec 2005 EUVL symposium, San Diego, November 8, 2005 8
Resist Profiles
50nm
40nm
Resist EUV-6
50nm
60nm
LBNL PSI
© imec 2005 EUVL symposium, San Diego, November 8, 2005 9
Resist ProfilesResist EUV-16
42nm
50nm
95 nm
45nm
50nm
40nm
PSILBNL
© imec 2005 EUVL symposium, San Diego, November 8, 2005 10
Resist Profiles
45nm
50nm
40nm
50nm
Through Dose
LBNL
Resist EUV-18
PSI
© imec 2005 EUVL symposium, San Diego, November 8, 2005 11
Main Differences Between LBNL and PSI
LBNL PSISchwarzschild Projection Optics Interference ImagingLimited DoF Virtually unlimited DoF~12% Estimated Flare No optics ⇒ ~0% FlareProcessing in chemically filtered environment
PEB hotplate next to beam line to minimize post-exposure delay; no chemical filtration
© imec 2005 EUVL symposium, San Diego, November 8, 2005 12
0.00.10.20.30.40.50.60.70.80.91.01.11.2
-50 -40 -30 -20 -10 0 10 20 30 40 50x (nm)
Rel
. Int
.
0.00.10.20.30.40.50.60.70.80.91.01.11.2
-50 -40 -30 -20 -10 0 10 20 30 40 50x (nm)
Rel
. Int
.
0.00.10.20.30.40.50.60.70.80.91.01.11.2
-50 -40 -30 -20 -10 0 10 20 30 40 50x (nm)
Rel
. Int
.
Aerial Images for 50nm L/S
Ideal
Including Flare (12%)
MET at LBNL
NILS = 5.1
NILS = 7.5
Interference PSI
Aerial image cannot be measured, but flare may be neglected. Aerial image is assumed to be a perfect sinusoid.
NILS = 3.1
© imec 2005 EUVL symposium, San Diego, November 8, 2005 13
Effect of Flare on Resist Performance
1st Exposure: Pattern
Interference PrinterMET @ LBNL
•Open frame exposure over exposed patterning fields.•Dose of open frame exposure determines added flare level: 0, 5, 10, 15%
Difference in aerial image (flare) is most likely candidate to explain the difference in resist profiles between LBNL and PSI. Some contrast demodulation experiments were performed.
© imec 2005 EUVL symposium, San Diego, November 8, 2005 14
Effect of Flare on Resist Performance
Interference PrinterMET @ LBNL
•Open frame exposure over exposed patterning fields.•Dose of open frame exposure determines added flare level: 0, 5, 10, 15%
2nd Exposure: Flare
60 μmshift
0, 10, 20, 30, 40% flare added
Difference in aerial image (flare) is most likely candidate to explain the difference in resist profiles between LBNL and PSI. Some contrast demodulation experiments were performed.
© imec 2005 EUVL symposium, San Diego, November 8, 2005 15
Contrast Demodulation at LBNLEUV-18No flare added
10% flare added
More scumming with increased ‘flare’.
15 mJ/cm212 mJ/cm2
18 mJ/cm2
15 mJ/cm212 mJ/cm2
18 mJ/cm2
© imec 2005 EUVL symposium, San Diego, November 8, 2005 16
Contrast Demodulation at LBNLEUV-18
No flare added
10% flare added
More scumming with increased ‘flare’.
© imec 2005 EUVL symposium, San Diego, November 8, 2005 17
Contrast Demodulation at LBNLEUV-18
No flare added
10% flare added
More scumming with increased ‘flare’.
© imec 2005 EUVL symposium, San Diego, November 8, 2005 18
Contrast Demodulation at PSI
50nm
45nm
Not Available
0% 10% 20% 30% 40%
EUV-16
T-topping with increased ‘flare’?!
© imec 2005 EUVL symposium, San Diego, November 8, 2005 19
Hypothesis
•Flare causes resist footing in cross-sections from LBNL exposures. •Airborne chemical contamination causes T-topping for high flare levels at PSI.•Difference in resist profiles between LBNL and PSI is caused by a combination of different flare and contamination levels.
0.00.10.20.30.40.50.60.70.80.91.01.11.2
-50 -40 -30 -20 -10 0 10 20 30 40 50x (nm)
Rel
. Int
.
40%
•Lower effective dose is applied for higher flare exposures.•This results in higher sensitivity for airborne chemical contamination.
0.00.10.20.30.40.50.60.70.80.91.01.11.2
-50 -40 -30 -20 -10 0 10 20 30 40 50x (nm)
Rel
. Int
.
0%
© imec 2005 EUVL symposium, San Diego, November 8, 2005 20
Prolith Simulations
0% 10% 20% 30%
0% 10% 20% 30%
With chemical surface
contamination
No chemical surface
contamination
40nm L/S
Flare level:
Flare level:
© imec 2005 EUVL symposium, San Diego, November 8, 2005 21
Outline
Introduction
Comparison of Resist Performance on Micro ExposureTool at LBNL and Interference Printer at PSI
‘Exposure Latitudes’ and Dose CalibrationResist ProfilesContrast Demodulation
Recent results on the interference printerChampion CAR dataPMMA results
Summary
© imec 2005 EUVL symposium, San Diego, November 8, 2005 22
2004 Champion DataChemically amplified resist
32.5nm40nm
30nm 25nm
EUV-6: Esize ~11mJ/cm2
© imec 2005 EUVL symposium, San Diego, November 8, 2005 23
Recent ResultsChemically amplified resist
30nm 25nm
32.5nm40nm
EUV-6 EUV-25Esize 11mJ/cm2 7.5mJ/cm2
Exp. Lat. (50nm)
18% 11%
LER (3σ) 7.1nm 5.7nmResolution 32.5nm 32.5nm
EUV-25: Esize ~7.5mJ/cm2
© imec 2005 EUVL symposium, San Diego, November 8, 2005 24
EUV-IL Results with PMMA
50 nm 45 nm 40 nm
32.5 nm 30 nm
Esize~50mJ/cm2
© imec 2005 EUVL symposium, San Diego, November 8, 2005 25
EUV-IL Results with PMMA
50 nm 45 nm 40 nm
35 nm 30 nm
Esize~50mJ/cm2
© imec 2005 EUVL symposium, San Diego, November 8, 2005 26
10
20
30
40
50
60
70
0 50 100 150 200
Dose (mJ/cm2)
Line
wid
th (n
m)
0 5 10 15 20 25 30
PMMA 50nmPMMA 40nmEUV-18 50nmEUV-18 40nm
CD vs. Dose for PMMA and EUV-18
© imec 2005 EUVL symposium, San Diego, November 8, 2005 27
Summary
EUV interference lithography is a powerful method for at-wavelength resist evaluation.
Good correlation found between MET and interference lithography in terms of CD through dose, but not for pattern profiles.
Difference in profiles caused by a combination of different levels in flare and airborne chemical contamination.
More surface inhibition of resists is needed to open profiles with realistic EUV flare levels.
Improvement for control of chemical contamination on interference printer is needed!
Modest progress in performance of chemically amplified resist materials has been observed during the past year.
Sub 35nm resolution is very challenging for all CAR materials, even with flare-free interference lithography.
Can the sensitivity of non-CAR materials be improved (by ~5x) to make suitable EUV resists?
© imec 2005 EUVL symposium, San Diego, November 8, 2005 28
Acknowledgements
Sematech (in specific Kim Dean) for providing exposure time on MET at LBNL.
Patrick Naulleau for assistance in exposures at LBNL and helpful discussions.
MEDEA+ for sponsoring through the ExCITe T406 program.
European Commission for sponsoring through the More Moore project.
© imec 2005 EUVL symposium, San Diego, November 8, 2005 29
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