Enhancing Resolution of the Albany Alpha-Demo Tool (ADT) with...

© 2012 IBM Corporation

Enhancing Resolution of the Albany Alpha-Demo Tool (ADT) with Pupil Filtering

EUVL Symposium 2012

Gregory McIntyrea, Leon Teeuwenb, Obert Woodc, Erik Sohmend, Daniel Corlissa, Theo van den Akkerb, Sander Boutenb, Eelco van Settenb, Oleg Voznyib, Sang-In Hanb, Hermann Biegd, Martin Burkhardta, Karen Petrilloa, Alexander Friza a IBM Corporation, Albany Nanotech, Albany, NY 12203

b ASML, Albany Nanotech, Albany, NY 12203

c GLOBALFOUNDRIES, Albany Nanotech, Albany, NY 12203

d Carl Zeiss SMT GmbH, Oberkochen, Germany

© 2012 IBM Corporation 2 G. McIntyre, 2012 EUVL Symposium, “Enhancing Resolution of the Albany ADT with Pupil Filtering”

Motivation & Outline

Outline:

Theory

Pupil filter concept

Optimum pupil filter designs

Standard imaging filters

Frequency doubling filters

Experimental results

22nm HP line-space

24nm HP contacts

Areas of development

Summary

Motivation: Enable next-node process development at select features

beyond the resolution limit of current tooling


3 beam imaging

Traditional imaging (ADT > 27nm HP)

nmNA

Lw 275.0(min)

Source is fixed tophat with =0.5

All on-axis illumination rays contribute to imaging

source

wafer Mask

HP = 27nm

=0.5

lens


Traditional imaging: Reduce HP below 27nm Central bundle of rays do not image

They provide DC background & reduce image contrast

Mask

HP < 27nm

=0.5


2 beam imaging

nmNA

Lw 1833.0(min)

Traditional imaging: Reduce HP below 27nm

Some rays provide 2 beam imaging

Central bundle of rays do not image

They provide DC background & reduce image contrast

Mask

HP < 27nm

=0.5


2 beam imaging

nmNA

Lw 1833.0(min)

Concept: standard filter

Eliminate rays that do not contribute to imaging

=0.5

Pupil Filter


Contr

ast

Half-pitch (nm) 16 19 22 25 28

Coherent rays

Concept: standard filter

Simple rectangular

example

Vary filter size 22nm HP with filter

provides comparable

contrast to 28nm HP without

filter

Exact benefit will depend

on capabilities of resist

Optimum filter size exists

for each pitch

Image Contrast

0

1

0.5 No Filter


Mask

Optimized line-space filter (standard imaging) Ensure 1st order

captured in pupil

0

2

4

6

8

10

20 22 24 26 28 30

No Filter

Filter

Dose +/- 5%

Mask Error +/- 0.5nm

Focus Error +/- 40nm

Good resolution and good CD

Uniformity to 22nm HP

Filter design through pitch

22 23 24 25 26 27 28 Half-pitch (nm)

Half-pitch (nm)

Sim

ula

ted

CD

U (

nm

)

22 23 24 25 26 27 28

Half-pitch (nm)

Acceptable imaging of isolated features (i.e.

SEM marks, Reticle align marks, etc.)

0

0.5

1

1.5

2

2.5

20 22 24 26 28 30

Dose

Multiplier

Half-pitch (nm)

Increase in dose required ~2.2x for 22nm HP


22x22HP Contact, capture minimum 1 order in each X and Y orientation

Optimized contact filter (standard imaging)

Image Cutline

Inte

nsity

Position

Aerial Image

0

5

10

15

20

25

30

22HP no filter 22HP filter

CDU_dose

CDU_meef

CDU_defocus

63% improvement in CDU

Mask S

imu

late

d C

DU

(n

m)

No Filter Filter

No Filter

Filter

Coherent rays

Filter design

No Filter Filter



X-orientation Half-pitch (nm)

22 23 24 25 26 27 21

Y-o

rienta

tion H

alf-p

itch (

nm

)

22

23

24

25

26

27

21

Optimized filters for various contact sizes


Square Contact Filters


0

2

4

6

8

10

12

20 22 24 26 28 30

Half-pitch (nm)

0

5

10

15

20

25

30

20 22 24 26 28

No Filter

Filter

Sim

ula

ted

CD

U (

nm

)

Do

se

Mu

ltip

lier

Half-pitch (nm)

Good resolution and good CDU

to ~22nm HP

Required dose increase likely limits

minimum HP to ~24nm


Concept: frequency doubling filter Increase mask pitch, block all of 0th order

Wafer pitch is frequency doubled (similar to ALT-PSM imaging)

=0.5

Freq. Doubled

2 beam imaging nm

NALw 5.1325.0(min)

Mask

HP = 2x wafer HP


15 16 17 18 19 20 14 21 22 23 24 Wafer half-pitch (nm)

Filter designs through pitch

Frequency doubling filter (1D line-space)

0

2

4

6

8

10

12

12 14 16 18 20 22 24 26

No Filter

Filter

Dose +/- 5%

Mask Error +/- 0.5nm

Focus Error +/- 40nm

Very small resolution and great CDU to ~15nm HP

Sim

ula

ted

CD

U (

nm

)

CDU

15nm HP

No Filter Filter


0

5

10

15

20

25

12 16 20 24

Do

se

Mu

ltip

lier

Half-pitch (nm)



Filter designs through pitch

Frequency doubling filter (1D line-space)

Poor printing of isolated features (requires alternate strategies for reticle

alignment, SEM navigation, etc.)

Reasonable dose multiplier

down to ~16nm HP


Frequency doubling filter (contacts)

Ideal design

21

30

Filter

Mask

Image

30nm HP square array on mask produces 21nm HP staggered array

22.6 24.0 25.5 26.9 28.3 29.7 21.2 31.1

Wafer half-pitch (nm)

23 26 29 32 20

Wafer staggered half-pitch (nm)

Image Contrast

Contr

ast

Through pitch with modified filter

Modified for

reasonable dose

21

30


Motivation & Outline

Outline:

Theory

Pupil filter concept

Optimum pupil filter designs

Standard imaging filters

Frequency doubling filters

Experimental results

22nm HP line-space

24nm HP contacts

Areas of development

Summary

Motivation: Enable next-node process development at select features

beyond the resolution limit of current tooling


Filter

Design

Half-pitch

Feature

Filter #

22LS

line-space

standard

line-space

standard

22LS 27x22CH 19LS 21CH

contact

standard

line-space

freq double

line-space

freq double

Type filter

1 3

24CH

contact

standard

2 4 5 6

6 Filter designs being tested experimentally

installed installed

In final processing, expected Oct ‘12

Status


Development and installation of

hardware solution (NA Handler)

complete

NA handler

Hardware enablement on ADT

Modified hardware originally

designed to allow multiple NA

settings

ADT-specific hardware solution


Pupil filter validation (22nm HP Line-space) Concept validated, showing ~20% improvement in ADT resolution

Resist process evaluation and development has begun

No Filter Resist D Resist B Resist C Resist A

With Filter

>10% Exposure latitude for 10% CD

0%

2%

4%

6%

8%

10%

12%

14%

16%

Slit 1 Slit 2 Slit 3 Slit 4 Slit 5 Slit 6

Resist A

Resist B

Resist C

Resist D

Exposure latitude for 10% CD


Resist process optimization ongoing

See also: Jun Hatakeyama, et al., “Reduction of LWR by Advanced

Polymer bound PAG based EUV resist” EUVL Symposium, 2012

Provided by Takashi Saito (TEL)


Mask LER transfer study with pupil filters

Photomask LER Transfer

Function with Pupil Filter (22HP)

SPIE Photomask 2012

Mask LWR

Programmed LER Mask

Resist LWR


Filter design Simulated image

in resist

No filter

Filter

24nm HP contacts

24nm HP contact filter (15% improvement in ADT resolution)

Fabricated filter

Successful printing in resist; beginning process development

No Filter With Filter


Pupil filtering: Areas of development

Slit uniformity: Presence of pupil

filter is impacting across slit intensity

uniformity optimization with unicom

blades.

Pupil filter No filter

Inte

nsity

Slit position Slit position

Optimized reticle alignment procedure to

improve reticle align repro and enable alignment

of frequency doubling filters

No filter

Pupil filter

Fla

re (

%)

Box size (um^2)

Out of Band stray light suspected to

be large with current filter.

Measurements show stray light in ~1um

range ~2x larger with filter installed.

Developed coating to minimize OoB reflections

Some filters redesigned to minimize stray light current redesign

22HP LS


Theory: Filters could enable ~12nm HP w/ NXE3300B

dipole90X

source

13 15 17 19 11

Half-pitch (nm)

Sim

ula

ted C

DU

(nm

)

13 14 15 16 12

Half-pitch (nm)

Filter designs

17

Concept could apply to any projection printing system with fixed illumination

Note: Hardware for filter exchange does not exist on NXE


Summary: Resolution enhancement with pupil filtering Demonstrated 20% improvement in resolution limit of ADT

Purpose is to enable process development at feature sizes beyond the

resolution limit of current tooling

Filters designed for optimum imaging performance of a specific feature

Hardware developed and installed on ADT for filter exchange

Experimental verification with 22HP line-space and 24HP contact filters

Concept extendable to any projection printing system with fixed illumination

Additional four filters in final fabrication 22HP LS 27x22 Via 38HP LS 42HP Via


Acknowledgements The authors would like to thank the following individuals and companies for

their assistance:

Brian Lee, Jerry Woods, Brian Niekrewicz, James Waddell (ASML)

Takashi Saito & Lior Huli (TEL)

Luke Orsini (IBM)

Matt Colburn, Cecilia Smolinski & David Mederios for management

support (IBM)

This work was performed by the Research Alliance Teams at various IBM

Research and Development Facilities


Backup


Dose requirements

High dose values required

depending on amount of light

blocked by filter

ADT maximum exposure

time per die is 830 seconds,

which can limit scan length

Current collector near end

of life; new collector expected

soon and should increase

power by >100%

Scan length [mm] as function of ALP [uW] per dose [mJ/cm^2]

0

5

10

15

20

25

30

35

40

0 5 10 15

ALP [uW]

Scan

len

gth

[m

m]

- o

vers

can

5mJ/cm^2

10mJ/cm^2

15mJ/cm^2

20mJ/cm^2

25mJ/cm^2

30mJ/cm^2

40mJ/cm^2

50mJ/cm^2

60mJ/cm^2

70mJ/cm^2

80mJ/cm^2

90mJ/cm^2

100mJ/cm^2

max die size

includingoverscan

Min scan

length

48CA 44LS

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