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

Slide 2

Public

NA=0.55


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Slide 3

Anamorphic magnification solves the angular spread at the mask Public

Y 0.33NA – Mag 4x

X

Multilayer Reflectivity


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Slide 4


Y 0.33NA – Mag 4x

X

Y - 4x

0.55NA – Mag 4x

X



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Slide 5


Y 0.33NA – Mag 4x

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Y - 4x

0.55NA – Mag 4x

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Y - 8x

0.55NA – Mag 4x/8x



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Slide 6

Anamorphic magnification: Circular exit pupil requires elliptical entrance pupil

Anamorphic

MAG 4x/8x

x

y

Public

Entrance pupil


Slide 7

Anamorphic magnification: Circular exit pupil requires elliptical entrance pupil Public

POB

MAG 4x/8x At reticle At wafer


Slide 8

Public

Contents

Mask

Central obscuration

Contrast

Summary & conclusions


Main consequences: Half field imaging, mask pattern is

stretched in scanning direction

x

y

MAG 4x in x

MAG 8x in y

Note: rectangular slit shown for illustration purposes

Slide 9

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)


Slide 10

• 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

1nm

mef* xx

mef* yx

d

2 d

d/4

d/4

Slide 11

2D features experience strong X-Y interaction for mask

CD errors Public


@ mask @ wafer

1nm

mef* xx

mef* yx

d

2 d

d/4

d/4

Slide 12


CD errors Public

@ mask @ wafer

mef* xy

mef* yy

1nm


@ mask @ wafer

1nm

mef* xx

mef* yx

d

2 d

d/4

d/4

Slide 13


CD errors Public

@ mask @ wafer

mef* xy

mef* yy

1nm

@ mask @ wafer

MEF* X

( mef* xx + mef* xy )

MEF* Y

( mef* yy + mef* yx )

1nm

1nm


Slide 14

contributors

@ mask @ wafer

1nm

1nm

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


Slide 15

Public

Contents

Mask

Central obscuration

Contrast



Standard EUV coatings cannot

handle these large angles

Substrate

Slide 16

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

ob

scu

red

Slide 17

Public

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

un

ob

scu

red

And even better:

The smaller angular

range increases the

transmission


Slide 18

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


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EL %

Half Pitch [nm]

with_obscurationwithout_obscuration

Slide 19

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)


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Slide 20

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

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EL %

k1 value [-]

with_obscurationwithout_obscuration0.33NA


DipoleY (20% pupil fill ratio)


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EL %

Pitch [nm]

with_obscuration

without_obscuration

Slide 21

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)


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EL %

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with_obscuration

without_obscuration

Slide 22

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

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EL %

k1 value [-]

with_obscuration

without_obscuration

0.33NA




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%]

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EL [

%]

Half Pitch [nm]


Slide 23

Public

High contrast through pitch maintained for 2D features

Dense contact holes through pitch



Quasar (20% pupil fill ratio)


Slide 24

Public

Obscuration has limited impact on non-telecentricity for 1D

features driven by Mask3D effects

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

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DipoleY (20% PFR)

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Small annular (20% PFR)


Slide 25

Public



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

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k1 value[-]

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0.33NA


DipoleY (20% PFR)

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Small annular (20% PFR)


Slide 26

Public



• Small compensation effect observed for semi-dense pitches

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cen

tric

ity-

Y [

mra

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Quasar (20% pupil fill ratio)

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cen

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Anamorphic Placement aware SMO mitigates non-

telecentricity Confidential

Slide 27

Pattern shift through focus Flat-Mask SMO source

Placement aware SMO source

Multi-pitch L/S pattern

18nm min. pitch

S1

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S7

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-0.3

-0.1

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Pat

tern

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ift

[nm

]

Defocus [nm]

S1

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S7

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Pat

tern

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ift

[nm

]

Defocus [nm]

S1

S2

S3

S4

S5

S6

S7

Anamorphic Placement aware SMO mitigates non-

telecentricity Confidential

Slide 28

• Max non-telecentricity reduces from 13 to 4mrad

Flat-Mask SMO source



18nm min. pitch

S1 S2 S3

S4 S5 S6

S7

Feature dependent non-telecentricity

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S1 S2 S3 S4 S5 S6 S7Te

lece

ntr

icit

y [m

rad

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Flat mask SMO

M3D SMO

Anamorphic Placement aware SMO restores

overlapping Process window Confidential

Slide 29

Exposure Latitude vs DoF Flat-Mask SMO source



18nm min. pitch

S1

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S7

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osu

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atit

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Anamorphic Placement aware SMO restores

overlapping Process window Confidential

Slide 30

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

Flat-Mask SMO source



18nm min. pitch

S1 S2 S3

S4 S5 S6

S7

Overlapping Process window

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po

sure

Lat

itu

de

[%

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Depth of Focus [nm]

Flat mask SMO

Placement aware SMO


Slide 31

Public

Contents

Mask

Central obscuration

Contrast



Slide 32

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

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0.55NA

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S [-

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Slide 33

Public

Local CDU dominant contributor to EPE – Mitigation

via image contrast enhancement


Slide 34

Public

Local CDU dominant contributor to EPE – Mitigation

via image contrast enhancement

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


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req

uir

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NIL

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5%

LC

DU

Half Pitch (nm)

17mJ 35mJ 70mJ

Slide 35

Confidential

High NA most powerful knob to control Local CDU and

dose requirements

Courtesy: Sander Wuister, Gijsbert Rispens

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req

uir

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S fo

r 1

5%

LC

DU

Half Pitch (nm)

17mJ 35mJ

70mJ NILS 0.33NA

NILS 0.55NA0

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Do

se [

mJ/

cm2

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NILS [-]

Dose to meet 15% LCDU requirement

for 18nm dense holes

0.33NA

0.55NA


Slide 36

Public

Contents

Mask

Central obscuration

Contrast



Slide 37

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


Slide 38

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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