NXE:3300 insertion for N7 : status and...

NXE:3300 INSERTION FOR N7 : STATUS AND CHALLENGESVicky Philipsen, Iacopo Mochi, Lieve Van Look, Gian Lorusso, Kim Vu Luong, Eric Hendrickx (imec)

Friso Wittebrood, Guido Schiffelers, Eelco Van Setten, Timon Fliervoet, Mircea Dusa (ASML)

2015 International Symposium on Extreme Ultraviolet Lithography - Oct. 5. - Maastricht

2015 International Symposium on Extreme Ultraviolet Lithography, Maastricht

INTRODUCTION

EUV insertion in N10 @imec

Critical Metal pitch = 48nm; Critical contacted poly pitch = 64nm

2D single patterning with EUV demonstrated

EUV insertion in N7 @imec

Critical Metal pitch = 28-36nm; Critical contacted poly pitch = 42nm

Different patterning options :

2

2D patterning with EUV 1D patterning with EUV 1D patterning with 193i MP

+ block with EUV

Scope of this work:

Generate experimental NXE:3300 data of N7 Metal compatible structures

to verify printability limits in support of N7 patterning choices

STATUS N7 PRINTABILITY

• resolution pitch for trenches

• tip-to-tip

• 2D constructs


STATUS N7 METAL PRINTABILITY

4

Based on

illumination

Resist readiness of CAR

3 resists evaluated

for

Resolution pitch for trenches

Tip-to-tip

2D constructs

using

NXE:3300 exposures at ASML-DEMO lab in Veldhoven

Annular

100%Quasar 45°

100%Quasar 24°

50%1D-SMO

100%

Tachyon SMO NXE FlexPupil

for 30nm pitch vertical

trenches and 24nm gaps

illumination efficiency


RESOLUTION PITCH

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SIMULATION of VERTICAL 1:1 TRENCHES

CPPMxP

• pitch 42nm (CPP) shows NILS well above 2 for Annular and Quasar illumination

• pitches around 32nm (MxP) require pupil optimization towards more Dipole-like setting

to get NILS > 2

100% ill. eff.

100% ill. eff.

50% ill. eff.

Tachyon

SMO NXE

FlexPupil 100% ill. eff.


RESOLUTION PITCH

6

WAFER VERIFICATION of VERTICAL 1:1 TRENCHES

• Experimental evaluation confirms decrease in resolution pitch by pupil optimization

• Pitches ≤ 32nm show line pinching further process optimization required

Pitch 36nm Pitch 34nm Pitch 32nm Pitch 30nm Legend:

Decent PW

Good imaging

at BE, BF only

No PW

Resist A

Resist A

Resist A

Resist B


Resist A

Resist B

Resist C

Quasar 24deg opening angle shows larger

EL than Quasar 45deg opening angle

Evaluated resists perform equally ~ 40mJ/cm²

EXPOSURE LATITUDE

7

WAFER VERIFICATION of VERTICAL 1:1 TRENCHES

• Contacted Poly Pitch 42nm for N7 can be easily achieved with Quasar illumination

• Metal x Pitch 34nm shows increasing EL with pupil optimization

Contacted Poly Pitch 42nm; Target CD 24nm

Large Annular has lower EL than Quasar;

in accordance with NILS

Evaluated resists perform equally ~ 40mJ/cm²

Metal x Pitch 34nm; Target CD 17nm

Resist A

Resist B

Resist C


TIP-TO-TIP PRINTABILITY

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in 2D patterns and 1D patterns

To enhance printability of generic tip-to-tip a hammer head is applied in the mask design:

printability of generic tip-to-tip evaluated :

Mask: Aerial

contour:

Mask: Aerial

contour:

Pitch

Gap

Pitch 36 and 40nm ; Gap 10, 14, 18, 22, 26nm

Hammer head extension 2nm; HH length 20nm Hammer head not optimized

2nm


TIP-TO-TIP PRINTABILITY

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ILLUMINATION IMPACT

• Pupil optimization for Metal x Pitch allows smaller printed tip-to-tip

• Printed gap CD is in range for the N7 requirement

illumination source has large impact in minimal printed gap

Quasar shape needed to print gaps around 23nm (i.e., N7 target gap)

illumination source has impact on dose sensitivity of printed gap

36nm 1:1 trench pitch printed through Gap width in resist B


PRINTABILITY OF 2D CONSTRUCTS

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Note:

OPC on mask was applied, not optimized for the

applied illuminations

Tip-to-tip 22nm

Pitch 38nm

Pitch 34nm

Contrast simulation:

Contrast 0.67 ~ NILS 2NILS ≥ 2 for good in-resist

performance

Target layer of 2D construct:

• Contrast is sufficient for Quasar and 2D-SMO illumination on three selected spots

Tachyon SMO

NXE FlexPupil

100% ill. eff.


PRINTABILITY OF 2D CONSTRUCTS

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ILLUMINATION IMPACT

• 2D printability can be improved by choosing the appropriate resist process

• Pupil optimization can further help 2D printability

Resi

st A

Resi

st B

47.7mJ/cm² 45.9mJ/cm² 46.8mJ/cm²

43.2mJ/cm² 41.4mJ/cm²

CHALLENGES IN EUV PRINTABILITY

• Best Focus shifts through pitch

• 2bar asymmetry through focus



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@ wafer level:

• H/V bias

• Best Focus shifts through pitch

• Pattern shifts through focus

• 2bar asymmetry through focus

Multilayer mirror

Patterned absorber

@ mask level:

• Mask topography

• Oblique incidence of EUV light

• Multilayer reflectivity

• Off-axis illumination


BEST FOCUS THROUGH PITCH

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• experimental manifestation of Mask 3D effect predicted by rigorous simulations

Vertical trenches through pitch (34nm to 88nm)

35nm

42nmExperimentally determined Best Focus through pitch are

illumination dependent

strongest at the smaller pitches (≤ 48nm)

predicted by rigorous mask 3D simulation


PROCESS WINDOWS THROUGH PITCH

15

• Mask 3D effect influences partly the overlapping process window

Overlapping process window is experimentally limited by smallest pitch

Depth-of-Focus of overlapping process window ~ 100nm

Total focus control of NXE:3300 ~ 110 70nm

Vertical trenches through pitch (34nm to 88nm)

overlapping DoF > total focus control

safe imaging regime


TWO BAR PRINTABILITY

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Pitch 36nm Horizontal in long pitch 1500nm

Best Focus difference between

LeftLower and RightTop trench

Vertical 2-bar

LeftL

ow

er

trench

Righ

tTop

trench

Cente

r Lin

e

Pitch

long pitch

BEST FOCUS DIFFERENCE



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BEST FOCUS DIFFERENCE

• experimental evidence of Best Focus difference partly due to Mask 3D and tool setting

Best Focus difference is pitch dependent

Best Focus difference is slit position dependent

Larger Best Focus differences for Dipole Y illumination

~center slit

Horizontal

~right edge slit

Horizontal



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CD DIFFERENCE THROUGH FOCUSPitch 36nm Horizontal in long pitch 1500nm

CD difference between

LeftLower and

RightTop trench

Horizontal 2-bar

LeftLower trench

RightTop trench

Center Line

Pit

ch

long

pitch

CD asymmetry through focus



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CD DIFFERENCE THROUGH FOCUS

• experimental manifestation of Mask 3D effect in 2-bar asymmetry through focus

CD asymmetry apparent in horizontal orientation

Dipole Y illumination induces stronger CD asymmetry than Quasar illumination

~center slit


CONCLUSION

Experimental EUV patterning exploration for N7 using 2D and 1D

on NXE:3300

with current resist processes

with moderate pupil optimization

demonstrates

trench pitch down to 34nm

printed gap CD down to 20nm

shows potential towards 32nm trench pitch

by pupil optimization

by resist process improvement

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STATUS N7 PRINTABILITY

2D patterning with EUV 1D patterning with EUV

Tachyon SMO NXE FlexPupil

with 100% ill. eff.

Resist B

Vertical pitch = 32nm; 1:1 L:S

Printed trench CD = 15.9nm

Nominal gap CD = 8nm

Printed gap CD = 26.5nm


CONCLUSION

show best focus shifts through pitch

show 2-bar asymmetry through focus

induced by mask 3D effect

need to be considered in design rules

or need mitigation strategies

illumination source optimization

OPC including assist features

mask absorber tuning

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Related work at this Symposium:

o Process variation in N7

o Eelco van Setten, this Session

o Mitigation of M3D effect

o Friso Wittebrood, this Session

o Kim Vu Luong, Session 9 on Wed.

o Resist process improvement

o Mieke Goethals, P-IM-06

towards EUV extendibility beyond N7


ACKNOWLEDGEMENTS

Maarten van Dorst, Peter Rademakers and the ASML DEMO team in Veldhoven

David Rio (ASML – Brion)

Panoramic

Synopsys

Osamu Inoue-san (Hitachi)

Berkcan Gokce, Mieke Goethals, Werner Gillijns, Jeroen Van de Kerkhove (imec)

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NXE:3300 insertion for N7 : status and...

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