microstepper vs. interference euv lithographyeuvlsymposium.lbl.gov/pdf/2005/pres/26 2-re-12...

© 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


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?


The Micro-Exposure Tool

Courtesy of Sematech/LBNL


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)


Outline

Introduction




Summary


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


Resist Profiles

50nm

40nm

Resist EUV-6

50nm

60nm

LBNL PSI


Resist ProfilesResist EUV-16

42nm

50nm

95 nm

45nm

50nm

40nm

PSILBNL


Resist Profiles

45nm

50nm

40nm

50nm

Through Dose

LBNL

Resist EUV-18

PSI


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


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


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.


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.


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


Contrast Demodulation at LBNLEUV-18

No flare added

10% flare added



Contrast Demodulation at PSI

50nm

45nm

Not Available

0% 10% 20% 30% 40%

EUV-16

T-topping with increased ‘flare’?!


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%


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:


Outline

Introduction




Summary


2004 Champion DataChemically amplified resist

32.5nm40nm

30nm 25nm

EUV-6: Esize ~11mJ/cm2


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


EUV-IL Results with PMMA

50 nm 45 nm 40 nm

32.5 nm 30 nm

Esize~50mJ/cm2


EUV-IL Results with PMMA

50 nm 45 nm 40 nm

35 nm 30 nm

Esize~50mJ/cm2


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


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?


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.

microstepper vs. interference euv lithographyeuvlsymposium.lbl.gov/pdf/2005/pres/26 2-re-12...

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