flcc seminar: lithography feb. 7 th, 2005 1 flcc seminar: psm lithography monitors garth robins and...

Seminar: Lithography Feb. 7th, 2005

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FLCC

FLCC Seminar: PSM Lithography MonitorsGarth Robins and Greg McIntyre UCB

FLCC Research Results: Photomasks as precision instruments for monitoring aberrations and polarization in projection printing with Professor Andy Neureuther

Design, SEM, AFM and AIMS results for 193 nm in collaboration with Photronics and AMD

February 7th, 2005


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FLCC

A special thanks to the following organizations and individuals for all of their tremendous help and support while conducting this research:

Photronics Bryan KasprowiczMarc CangemiRamkumar Karur-ShanmugamRand CottleJustin NovakMark Smith

AMD Jongwook KyeHarry LevinsonAlden Acheta

UC Berkeley Frank GennariGarth Robins


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FLCC

Polarization

Illumination

PSM Performance

Fogging

Flare

Trans Imbalance

Aberrations

Immersion

Design / Process variation

Metrology

CMP

Resist

* Screenshots taken in Frank Gennari’s Simple Display

Multi-Student Process-EDA Test Mask


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FLCC

Feature Level Compensation and Control

PSM Polarimetry: Monitoring Polarization at 193nm High-NA and

Immersion with Phase Shifting Masks

Greg McIntyre

[email protected]


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FLCC

• High-NA / Polarization Effects• PSM Polarimeters: Concept• Initial Experimental Results• Improved Design• Simulated Examples• Mask Topography Effects• Proposed Reticle Design

PSM Polarimetry: Outline


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Background: High NA Vector Effects

Z – component leads to:• Image reversal of TM component, Loss of depth of focus, Loss of image contrast

xz

y

Low NA

= ETM NAEz = ETM sin()

High NA

Z component of E-field introduced at High NA from radial pupil component

Z-component negligible

TMTE

mask

wafer


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• Z Component is derivative of XY components

• Polarization Monitor maximizes z-component proximity effect in pattern center for one polarization component (reciprocity)

)()()()()sin()(00

xExk

jxE

k

kxE

n

NAxExE TMTM

xTM

resistTMz

PSM Polarization Analyzer: Concept

X polarization Ez PSF Y polarization Ez PSF

PSF (Airy pattern)

y

x

0

180

Cr

• Proximity effect (point spread function) derived for z-component

kx

ko


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Increasing NA

EoyEoxMask

Wafer

xz

y

TM

TE

Similar Effect Observed by Monitoring Nulls of Periodic Alternating-Phase Grating

Linear

Radial


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0 180

13.34 mJ/cm

0.52 % CF

14.4 mJ/cm

0.49 % CF

Signal is dose when center resist just clears

FLCC Test Mask: Experimental Verification of High-NA Signal (Jan 05)

• 4-phase PSM test mask provided by Photronics• Original concept: periodic 0-180 radial grating

MaskLayout

0 180

Proposed Design Improvement

Resist

Incr

easi

ng d

ose


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FLCC

HorizontalCutline(at center)

VerticalCutline

(center)

TE(y) linear TM(x) linear 45 linear 135 linear unpolarizedor circular

Mask pattern

0

1

2

3

4

TE(y) l

inear

TM(x

) line

ar

45 lin

ear

135

linea

r

unpo

larize

dCen

ter

Inte

nsi

ty (

CF

)Central intensity signal shows excellent response: Linear Polarization Patterns (simulation)

Signal

Simulated resist image

Dose


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FLCC

0.0

0.5

1.0

1.5

2.0

R L un-polarized

R

L

R

L

018090270

Circular Polarization Analyzers:

UnpolarizedRight Circular Left Circular

Incident light

pattern

Cen

tral

Int

ensi

ty (

%C

F)


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Off-Axis Polarization Analyzers:

090

180270

+ =

Introduce 4-phase linear progression to monitor polarization from off-axis illumination

Mask making becomes quite challenging

M

c NAP =

MaskSEM


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FLCC

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7

BPM TE

BPM TM

BPM 45

BPM 135

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1 2 3 4 5

TE

TM

45

135

unpol

Proposed Technique: Polarimeter = 6 analyzers

On-Axis

135

TM

Off-Axis

TE 45 TM 135 TE

018090270

45

TE

45 135

TE 45 TM 135 TE

Response: symmetric Response: asymmetric


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FLCC

Compare intended design to a (simulated) actual measurement:• Intended (80% TE polarized, 20% unpolarized) • Actual (70% TE polarized, 30% unpolarized).

0 1 2 3 4

L

R

135

45

TM

TE

Actual

Intended

Response (center Intensity / clear field)

Signal change for on-axis test case

Ana

lyze

r -15.7%CF

+15.7%CFNo change

No change

+1.9%CF

-1.9%CF

On-Axis Off-Axis135

TM

45

TE

135

TM

45

TE

0 0.5 1 1.5

135

45

TM

TE

Actual

Intended

Response (center Intensity / clear field)

Signal change for off-axis test case

Ana

lyze

r +6.4%CF

-9.1%CF

-1.1%CF

+0.6%CF

Practical Example: Response for two polarization states

>1% CF/ % polarization >0.5% CF/ % polarization (including expected resist effects)


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TE TM

Mask Topography Effects: Off-Axis Analyzer

1) Thin simulation Thick for only Case B

LPG only jumbles one polarization component (local TM)

2) Thin cases are not symmetric2 effects in same plane get jumbled – introduce 0 order

i.e. redirection (LPG) and diffraction (RPG)

0

0.2

0.4

0.6

0.8

1

1.2

Incident Light

Central Intensity

TE TM

ThinThickTE

TM

45


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FLCC

0

1

2

3

4

00.50.81

TE linea

r

TM lin

ear

45 lin

ear

135

linea

r

unpo

larize

d

Cen

ter

Inte

nsi

ty (

CF

)

c

TM Analyzer: Signal deterioration due to mask topography as mask dimensions decrease (i.e. c increases)


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FLCC

4-phase linear phase progression difficult to manufacture


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PSM Polarimeters require very coherent illumination, perhaps provided by a pinhole on backside of reticle

Cluster (frontside reticle)

Pinhole (in chrome on backside reticle)

Radius ~ 100um

polarimeter

))(tan(arcsinMn

NAtr

g

Crpolarimete

t = mask thicknessng = mask index of refractionC = monopole location

Proposed Test Reticle Design


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Summary • Monitors derived from basic principles• Initial experimental results appear to validate principles of technique• Simulated examples of new design promise to monitor polarization:

• 1 %CF / % polarization state (on-axis)• 0.5 %CF / % polarization state (on-axis)

• Discussed practical limitations• Proposed test reticle design


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Feature Level Compensation and Control

Aberrometry: Are pattern and probe aberration monitors ready for prime time?

Garth [email protected]


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Aberrometry: Outline• λ = 193nm AIMS

results

• Factor targets into components

• Lithography demons

• Improve performance through adjusting design dimensions

•0°•90°•180°•270°

Probe

Rings

defocus


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~BF

1 step = 0.145 RU

•0°•90°•180°•270° defocus

• Alternating 0°/180° phase-shifted rings surrounding a 90° phase-shifted probe

• Aberration perturbs spillover electric-field

• Sensitivity > 60%CF/1RU

Response to focus

How Targets Work

AIMS imageMask layout

AIMS intensity cut

2RZ3055cr_all

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 5 10 15 20Focal Plane

Pea

k In

tens

ity (1

00%

C

F)

0° probeT3 (90° probe)T3 0° outer ring

-1RU +1RU

T3 center probe

Isolated probe0° outer ring


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AIMSTM

TEMPEST

Litho.SEM

SPLAT 6.0

Mask EM effects High-NApolarization effects

Mask erroreffects

Resist effects

SPLAT

• 0°/90°/180° phase region intensity imbalance

• Reduced coupling of TE mode (TM contrast ↓)

• Mitigation of high-angle effects (n)

• Mask geometry

• Pixilation

• Layer registration

Panoramic

SimulationExperiment

This poster Lithography Demons


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• Factor target into elements and parameterize

• 0°/90°/180°/270° phase-shifted rings, probes, lines, and rings surrounding probes

• λ = 193nm, NA = 0.80

•0°•90°•180°•270°

Probe

Rings

defocus

r_cr neck

• λ = 193nm, NA = 0.80, σ = 0.3• 1 RU = 42 (λ / 2 NA2) = 2.4125 μm

Strategy of Factorization


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• 4-phase multi-student test mask fabricated and donated by Photronics, Inc. as part of UC Berkeley’s Feature Level Compensation and Control grant

• Process: chrome open, then 90°, then 180° phase etch w/ bias

• Position, programmed bias, processing (pullback)

• Measure edge bias on isolated lines and probes

Mask Making Flow & Tolerances1) Open all cr

2) 90° etch (for 90° & 270° regions)

3) 180° etch (for 270° & 180° regions)

Potential errors

Alignment/etch depth/effective phase

Quartz

Quartz

Quartz

90°270° 0°180°


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• SEMs indicate biases & alignment

• Observe isolated probes + full 2-ring defocus target

Mask Making Results

90°0° 270°180°

Nominal-sized iso-probes

2-Ring defocus target

90°

0°180°

cr

Layer Edge bias (nm) Alignment (nm)

Chrome

(e-beam)

+14+40 NA

90° -53 0

180° -31 36

270° See iso probe See iso probe


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Performance of Isolated Lines

2-Ring defocus target

Iso-lines in dark field

-20

-15

-10

-5

0

5

10

15

20

25

0 100 200 300 400 500

Mask design width/2 (nm)

Ed

ge

bia

s (f

abri

cate

d -

d

esig

n)

(nm

)

0° Line90° Line180° Line270° Line

AIMSFab 193nm

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 90 180 270Nominal Line Phase

Pea

k In

ten

sity

(10

0% C

F)

@ B

F 0nm50nm100nm120nm150nm200nm250nm

AIMSFab 193nm

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 50 100 150 200 250 300Measured Linewidth (nm)

Pea

k In

ten

sity

(10

0% C

F)

@ B

F

0° line180° line0° Ring180° RingSPLAT

0.207 λ/NA 1.04 λ/NA

NA = 0.80, σ = 0.3

0°SPLAT

180°

• Bias(size, phase) (L)

• Peak intensity (R)

• Typical linewidth = 150nm

• MEEF = 1.3

wnom = 150nm

Design Width


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• Bias(size, phase) (L)• Peak intensity (R)• Edge effects in phase

etched holes are important

Performance of Isolated ProbesNA = 0.80, σ = 0.3

Iso-probes in dark field

-20

-15

-10

-5

0

5

10

15

0 100 200 300 400 500

Mask design radius (nm)

Ed

ge

bia

s (f

abri

cate

d -

d

esig

n)

(nm

)

0° Probe90° Probe180° Probe270° Probe

AIMSFab 193nm

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 90 180 270Nominal Iso-Probe Phase (deg.)

Inte

nsi

ty (

100%

CF

)

0nm50nm100nm120nm150nm200nm250nm

AIMSFab 193nm

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 50 100 150 200 250 300Iso-Probe Measured Diameter (nm @ wafer)

Inte

nsity

@ B

est

Focu

s (1

00%

CF)

0.207 λ/NA

rnom = 109nm

Design Diameter

0°180°

SPLAT

1.04 λ/NA


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• Look at 2R_035cr targets iso-rings• λ = 193nm, NA = 0.80, σ = 0.3• 1 RU = 42 (λ / 2 NA2) = 2.4125 μm• 11 focal planes, 0.7 μm steps• 1 step = 0.290 RU (programmed)

81.5% CF

98.1% CF

~1.2×

79.5% CF

42.3% CF

~1.9×

Example of Rings

0° 180° 0°

180° 0° 180°

• Single 0° & 180° rings of different sizes & thicknesses w/ no probe

• Ring intensity vs. center intensity

• MEEF


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Iso-Rings (σ = 0.3)

0

0.2

0.4

0.6

0.8

1

1.2

120 130 140 150 160 170

Measured Width (nm)

Inte

nsi

ty (

100%

CF

)

Ring (0°)

Ring (180°)

Performance of Rings

• Peak intensity difference with phase is as-expected (L)

• Center spillover is also strongly dependant upon ring phase (R)

• Response through focus is same for thickest ring (B)

Z3 Iso-ring

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 2 4 6 8 10

Focal Plane

Inte

nsi

ty (

100%

CF

)

L 180° iso_ ring_ ir1

M 0° iso_ ring_ ir2

S 180° iso_ ring_ ir3

L 0° iso_ ring_ ir4

M 180° iso_ ring_ ir5

S 0° iso_ ring_ ir6

Center spillover response to focus

Iso-Rings (σ = 0.3)

0

0.2

0.4

0.6

0.8

1

1.2

120 130 140 150 160 170

Measured Width (nm)

Inte

nsi

ty (

100%

CF

)

Center (0°)

Center (180°)

0°180° 0°180°

Ring Intensity Center Intensity


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FLCC

Performance of Probeless Targets

2RZ3055cr_all

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6


Pea

k In

ten

sity

(10

0% C

F)

0° probeT1 (no probe, 180° inner ring)T4 (no probe, 0° inner ring)

• Two 2-Ring defocus targets shown with no probes

• Response through focus is quite strong even without probe

• Expect symmetric shift from BF between the targets

• Bias, intensity imbalance, & phase etch error contribute to non-ideality

Center Intensity


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Target Synthesis Via Phasor Diagram

• 90° probe & expected performance

• Non-idealities: truncation/Z0, phase etch, probe size, intensity imbalance/spillover– Probe length is smaller than intended

– Probe likely rotated due to an EM effective phase error & additional phases in hole

– Unwanted length changes are produced by bias

– Unwanted rotation is due to effective phase etch

– Extra component due to finite size and bias

Re

Im

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0

Defocus (RU)

Inte

ns

ity

(1

00

%C

F)

2pE

22Rp EE

2RE

0pE

2RE

22 pE

constantEandE Rp

Re

Im

?

Ideal phasor diagram

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0

Defocus (RU)

Inte

nsi

ty (

100%

CF

)

SPLAT

19%

34%

Lateral shift

Center intensity

Iso-probe intensity


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FLCC

•0°•90°•180°•270° defocus

Mask layout2RZ3055cr_all

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6


Pea

k In

tens

ity (1

00%

C

F)

1 step = 0.145 RU

• 2-Ring defocus target w/ 90°, 270°, & “no probe”

• “No probe” target should be symmetric about BF

• “No probe” ~ 270° probe

• 90° brighter at BF

Target Measurements Revealing Phasor Gotchas

-1RU +1RU

Isolated probe

90°

270°

No probe

Center Intensity

• Complimentary 90°/270° probe target responses should be reflected about BF, but not symmetric


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FLCC

0

1

2

3

4

5

6

7

0 2 4 6 8 10

Target

Po

siti

on

of

Min

imu

m(F

oca

l P

lan

e)

Position of minimum

Focal plane of Strehl peak

ip1T3

Peak

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 2 4 6 8 10

Focal Plane

Inte

nsi

ty (

100%

CF

)

2rz3_035cr_ip1_017sig_recheckABCDEFGHI

1000 pixels

1000

pix

els

A

B

C

D

E

F

G

H

I

A B C D E F G H I

• Image one 2-ring defocus target at 9 positions in the AIMS field

• Could be a tilt in both X & Y

Measuring AIMS Field Flatness


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FLCC

Summary• PAP designed, fabricated and tested on AIMS• Strategy of factoring insight into factors contributing to 2nd-

order effects in the phasor addition of the composite performance

• Sub-printable probe intensities weaker than expected performance nearly that of a probeless design.

• Nearly probeless… still useful w/ ~50% of the CF/RU defocus (away from best focus)

• Target components reveal ideas for monitoring mask making…

• MEEF• Overall the targets gave a much stronger and more sensitive

signal to focus that isolated probes (Strehl ratio) and with further sizing and target phase combinations both focus and EM performance can be extracted

flcc seminar: lithography feb. 7 th, 2005 1 flcc seminar: psm lithography monitors garth robins and...

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