EUV high NA anamorphic imagingeuvlsymposium.lbl.gov/pdf/2016/Oral/Wed_S2-3.pdf2016 International...

2016 International Symposium on Extreme Ultraviolet Lithography, Hiroshima, Japan

EUV high NA anamorphic imaging

It’s all about the angles Oct-26-2016 Eelco van Setten, Gerardo Bottiglieri, Thorsten Last, Alberto Colina, Jan Lubkoll, Gijsbert Rispens, Jan van Schoot

EUV: it’s all about the angles High-NA comes with large angles

ML reflection MoSi Multilayer

Public

NA=0.55

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Angle of incidence on the mask [deg]

Multilayer

Anamorphic magnification solves the angular spread at the mask Public

Y 0.33NA – Mag 4x

Multilayer Reflectivity

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Multilayer

Y 0.33NA – Mag 4x

Y - 4x

0.55NA – Mag 4x

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Multilayer

Y 0.33NA – Mag 4x

Y - 4x

0.55NA – Mag 4x

Y - 8x

0.55NA – Mag 4x/8x

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

]Angle of incidence on the mask [deg]

Multilayer

Anamorphic magnification: Circular exit pupil requires elliptical entrance pupil

Anamorphic

MAG 4x/8x

Public

Entrance pupil

Anamorphic magnification: Circular exit pupil requires elliptical entrance pupil Public

MAG 4x/8x At reticle At wafer

Public

Contents

Central obscuration

Contrast

Summary & conclusions

Main consequences: Half field imaging, mask pattern is

stretched in scanning direction

MAG 4x in x

MAG 8x in y

Note: rectangular slit shown for illustration purposes

Public

Anamorphic masks:

• Image field half of current size

• Mask pattern stretched

Feature distortions on mask

• 4x-direction will drive mask

requirements (CD, registration

and defectivity)

• Traditional Mask Error Factor (MEF) is normalized with the magnification:

𝑀𝐸𝐹 =∆𝐶𝐷𝑤𝑎𝑓𝑒𝑟

∆𝐶𝐷𝑚𝑎𝑠𝑘𝑚𝑎𝑔

• Not convenient for anamorphic Same MEF corresponds to different mask

CD tolerance in X and Y

• A new Mask Error Factor, MEF*, is defined:

𝑀𝐸𝐹∗ =∆𝐶𝐷𝑤𝑎𝑓𝑒𝑟

∆𝐶𝐷𝑚𝑎𝑠𝑘

1nm mask CD error gives ‘MEF*’ nm wafer CD error

New MEF definition to handle difference in X,Y-

magnification Public

@ mask @ wafer

mef* xx

mef* yx

2D features experience strong X-Y interaction for mask

CD errors Public

@ mask @ wafer

mef* xx

mef* yx

CD errors Public

@ mask @ wafer

mef* xy

mef* yy

@ mask @ wafer

mef* xx

mef* yx

CD errors Public

@ mask @ wafer

mef* xy

mef* yy

@ mask @ wafer

MEF* X

( mef* xx + mef* xy )

MEF* Y

( mef* yy + mef* yx )

contributors

@ mask @ wafer

Mask error in X-direction dominates error on wafer in

both directions

MEF* Y

( mef* yy + mef* yx )

MEF* X

( mef* xx + mef* xy )

Public

Mask error in X-direction

Public

Contents

Central obscuration

Contrast

Standard EUV coatings cannot

handle these large angles

Substrate

Public

Multi-layers set limits to angles & angular spread Angles must be reduced for high-NA optics

We have to limit the

angles on the mirror

we need another trick!

Angles and

angular spread

decrease

Public

There is a solution: We drill a hole into the mirror. Smaller angles enable transmission gain vs non-obscured NA 0.33

And even better:

The smaller angular

range increases the

transmission

Confidential

Obscuration may result in:

- application dependent

contrast loss

- Non-telecentricity

Obscuration radius limited to

20% of the pupil radius

( = 4% of the pupil area )

Obscuration comes at expense of blocking parts of

diffraction orders

8 12 16 20 24 28 32 36 40 44 48

Half Pitch [nm]

with_obscurationwithout_obscuration

Public

Contrast loss for semi-dense pitches using Dipole

illumination large part diffraction order blocked

• Worst point has acceptable Exposure Latitude

• Mitigation by means of SMO and SRAFs (for 16nm HP and up)

Horizontal L/S through pitch

DipoleY (20% pupil fill ratio)

8 12 16 20 24 28 32 36 40 44 48

Half Pitch [nm]

Public

Contrast loss for semi-dense pitches using Dipole

illumination large part diffraction order blocked

• Worst point has acceptable Exposure Latitude

• Mitigation by means of SMO and SRAFs (for 16nm HP and up)

• Contrast unobscured pitches very similar to 0.33NA for identical k1 values

0.25 0.5 0.75 1 1.25 1.5 1.75 2

k1 value [-]

with_obscurationwithout_obscuration0.33NA

DipoleY (20% pupil fill ratio)

20 30 40 50 60 70 80 90 100

Pitch [nm]

with_obscuration

without_obscuration

Public

Negligible contrast loss for illumination shapes of which small

part diffraction orders is blocked

12nm horizontal spaces through pitch

Small annular (20% pupil fill ratio)

20 30 40 50 60 70 80 90 100

Pitch [nm]

with_obscuration

without_obscuration

Public

Negligible contrast loss for illumination shapes of which small

part diffraction orders is blocked

• Contrast very similar to 0.33NA for identical k1 values

0.25 0.5 0.75 1 1.25 1.5 1.75 2

k1 value [-]

with_obscuration

without_obscuration

0.33NA

10 12 14 16 18 20 22 24 26 28 30

Half Pitch [nm]

10 12 14 16 18 20 22 24 26 28 30

Half Pitch [nm]

Public

High contrast through pitch maintained for 2D features

Dense contact holes through pitch

Quasar (20% pupil fill ratio)

Public

Obscuration has limited impact on non-telecentricity for 1D

features driven by Mask3D effects

• Compensation by SMO (asymmetric illumination) or mask stack optimization

8 12 16 20 24 28 32 36 40 44 48

Half Pitch [nm]

DipoleY (20% PFR)

20 30 40 50 60 70 80 90 100

Pitch [nm]

with_obscuration

without_obscuration

Small annular (20% PFR)

Public

• Compensation by SMO (asymmetric illumination) or mask stack optimization

8 12 16 20 24 28 32 36 40 44 48

Half Pitch [nm]

0.25 0.5 0.75 1 1.25 1.5 1.75 2

k1 value[-]

with_obscuration

without_obscuration

0.33NA

DipoleY (20% PFR)

20 30 40 50 60 70 80 90 100

Pitch [nm]

with_obscuration

without_obscuration

0.25 0.5 0.75 1 1.25 1.5 1.75 2

k1 value [-]

with_obscuration

without_obscuration

0.33NA

Small annular (20% PFR)

Public

• Small compensation effect observed for semi-dense pitches

10 12 14 16 18 20 22 24 26 28 30Tele

Half Pitch [nm]

Quasar (20% pupil fill ratio)

10 12 14 16 18 20 22 24 26 28 30Tele

Half Pitch [nm]

Anamorphic Placement aware SMO mitigates non-

telecentricity Confidential

Pattern shift through focus Flat-Mask SMO source

Placement aware SMO source

Multi-pitch L/S pattern

18nm min. pitch

-15 -5 5 15

Defocus [nm]

-15 -5 5 15

Defocus [nm]

Anamorphic Placement aware SMO mitigates non-

telecentricity Confidential

• Max non-telecentricity reduces from 13 to 4mrad

Flat-Mask SMO source

18nm min. pitch

S1 S2 S3

S4 S5 S6

Feature dependent non-telecentricity

S1 S2 S3 S4 S5 S6 S7Te

] Multi-pitch spaces

Flat mask SMO

M3D SMO

Anamorphic Placement aware SMO restores

overlapping Process window Confidential

Exposure Latitude vs DoF Flat-Mask SMO source

18nm min. pitch

0 30 60 90 120

Defocus [nm]

0 30 60 90 120

Defocus [nm]

Anamorphic Placement aware SMO restores

overlapping Process window Confidential

• Overlapping PW @ 10% EL increases from 36 to 64nm

Flat-Mask SMO source

18nm min. pitch

S1 S2 S3

S4 S5 S6

Overlapping Process window

0 20 40 60 80Ex

Depth of Focus [nm]

Flat mask SMO

Placement aware SMO

Public

Contents

Central obscuration

Contrast

Public

0.55NA gives high image contrast down to 8nm L/S

and 10nm contact holes

NILS vs resolution for 1D L/S NILS vs resolution for Contact holes

5 10 15 20 25

Half pitch [nm]

0.33NA

0.55NA

5 10 15 20 25 30

Half pitch [nm]

0.33NA

0.55NA

Public

Local CDU dominant contributor to EPE – Mitigation

via image contrast enhancement

Public

Local CDU dominant contributor to EPE – Mitigation

via image contrast enhancement

Jo Finders, SPIE 2016 and Fraunhofer IISB Litho simulation workshop 2016

10 15 20 25 30

Half Pitch (nm)

17mJ 35mJ 70mJ

Confidential

High NA most powerful knob to control Local CDU and

dose requirements

Courtesy: Sander Wuister, Gijsbert Rispens

10 15 20 25 30

Half Pitch (nm)

17mJ 35mJ

70mJ NILS 0.33NA

NILS 0.55NA0

1 2 3 4 5 6

NILS [-]

Dose to meet 15% LCDU requirement

for 18nm dense holes

0.33NA

0.55NA

Public

Contents

Central obscuration

Contrast

Confidential

Summary and conclusions

It’s all about the angles • Anamorphic imaging solves the angular spread at the mask

• M3D effects similar to 0.33NA

• Central obscuration enables high throughput with good imaging performance

• Anamorphic SMO does the rest

EUV High NA • Increased resolution enabling 8nm HP imaging

• Above all… superior contrast

• Key for reducing LCDU and EPE budget for maintaining shrink roadmap

Public

The authors would like to thank:

• Sander Wuister

• Jo Finders

• Stephen Hsu (Brion)

• Matthias Rösch

• Jens Timo Neumann

• Paul Graüpner

• Jörg Zimmerman

• Bernard Kneer

• Sacha Migura

Thank you for your

attention !

EUV high NA anamorphic imagingeuvlsymposium.lbl.gov/pdf/2016/Oral/Wed_S2-3.pdf2016 International...

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