Resolution, LWR, and sensitivity improvement on polymer...

October 19, 2009

Resolution, LWR, and sensitivity improvement on polymer-based

resist materials

Shinji Tarutani, Hideaki Tsubaki, Tooru TsuchihashiFUJIFILM CorporationElectronic Materials Research Laboratories

　

　　　　　　　　　 October 19, 2009

Outline

1. Challenges to EUV resist materials

2. Design policy to overcome RLS trade-offs

3. Technologies to improve RLS

4. Summary

　

　　　　　　　　　 October 19, 2009

1. Challenges to EUV resist materials

LWR

Resolution

Eopt

Simultaneous improvement of resolution, LWR and sensitivity

Critical issues of EUV resist

Will CAR indeed be able to meet the requirements for 22 nm HP spec and beyond?

What technologies would be needed to do them?

　

　　　　　　　　　 October 19, 2009

1. Challenges to EUV resist materialsLithographic performance of a CAR

• Basically 25nm HP resolution, 5nm LWR and 12mJ/cm2 sensitivity were demonstrated. These are still far behind the target.

ResolutionResolution LWRLWR SensitivitySensitivity

22 (22 (nm)nm) < 10 (< 10 (mJmJ/cm/cm2 2 ))12.2 (12.2 (mJmJ/cm/cm2 2 ))Performances Performances 25 (25 (nm, partially)nm, partially) 5.0 (5.0 (nm)nm)

ITRS HVM SpecsITRS HVM Specs < 2.2 (< 2.2 (nm)nm)

　

　　　　　　　　　 October 19, 2009


The first : Dependence of LWR and sensitivity on quencher amount

LWR is improved by increasing the loading amount of quencher with losing sensitivity. How would LWR be improved without losing sensitivity?

⇒ Large amount of generated acid⇒ Acid (de-protection) contrast enhancement

Two important results leading to our design policy

Ecd=30nm vs LWR @ L30P60

123456789

10

0 10 20 30 40 50 60

EUV_Ecd=30nm Sensitivity [mJ/cm2]

EU

V_L

WR

@ L

30P

60 [n

m]

Increasing loading amount of quencher

(SPIE 2007)

MET@ALS

EUV exposure

2

4

6

8

10

LWR

, nm

Dose to size, mJ/cm2

0 10 20 30 40 50 60

　

　　　　　　　　　 October 19, 2009


EUV exposure

MS-13 Microstepper (NA=0.3), FT=125 nm, PB = 120 oC/ 90 sec, PEB = 110 oC/90sec, Dev.= TMAH 2.38% 60 sec,

80 nm 70 nm 60 nm 50 nm 45 nm

HighMw

40 nm

Mid.Mw

LowMw

Resolution is improved by lowering the Mw of polymer.

⇒ Minimization of dissolution unit size

The second : Dependence of resolution on polymer MWTwo important results leading to our design policy

　

　　　　　　　　　 October 19, 2009


LWR

Resolution

Eopt

Simultaneous improvement of resolution, LWR and sensitivity

Design policy to overcome those trade-offs

Large amount of generated acid

Acid (de-protection) contrast enhancement

Minimization of dissolution unit size

Critical issues of EUV resist

　

　　　　　　　　　 October 19, 2009


Enhancement of Aerial Image Contrast

e-

EUV

Resist

Acid

e- trapAcid quencher

e-

e-

e-

〔Deprotection〕

x

①

②

③④

Enhance electron generation①

Reduce electron diffusion②

Enhance acid generation③

Reduce acid diffusion④

Increase ionization efficiency

Increase ionization points

Increase EUV absorption

Decrease free vol. of matrix

PAG bounded matrix

Increase acid gen. efficiency

Increase PAG anion size

Increase electron trap density

Increase electron trap ability

Photo decompose quencher

Increase quenching ability

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 1 ; Increase of electron trapping density

0

2

4

6

8

10

0 5 10 15 20

Dose to size (μC/cm2)

Rel

ativ

e am

ine

conc

entra

tion

PAG 0.54XPAG 1XPAG 2XPAG 3XPAG 6X

Increase of PAG loadingIncrease of PAG loading

==

Correlates to [Acid] Correlates to [Acid] generated by exposuregenerated by exposure

E-beam exposure

Acid generation yield increased by increasing PAG loading, Acid generation yield increased by increasing PAG loading, but saturated at high PAG loadings.but saturated at high PAG loadings.

C. R. Szmanda, et al,, J. Vac. Sci. Technol. B 17, 3356 (1999).

[PAG]: Low[Polymer]: High

[PAG]: High[Polymer]: Low

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 2 ; Increase of electron trapping ability

Polymer

①②Secondary

electron generation

Electron trap and acid generation

PAGCH2 CH

OH

S O3S-Ar

CH2 CH

OH S

O3S-ArAr-SO3H

+ e

EUV

R

R

Polymer ionization Electron trapping ability- PAG loading- PAG electron affinity

Strategy to individually enhance (1) polymer ionization frequencStrategy to individually enhance (1) polymer ionization frequency y and (2) electron trapping ability of PAG should be required.and (2) electron trapping ability of PAG should be required.

R

Proposed mechanism

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 2 ; Increase of electron trapping ability

Higher reduction potential (V) of PAG gave larger amount of generated acid.

S

Z

X

Y0.0

0.5

1.0

1.5

2.0

2.5

-2 -1.5 -1 -0.5 0

reduction potential (V)

genera

ted

acid

(re

l.)

Y：non-bond

Y：single bond

Y：SO2

Electron trapping ability of PAGs

　

　　　　　　　　　 October 19, 2009


Energy diagram for an electron in resist matrix

PAG-1 PAG-2

e-

Electron

HOMO

LUMO

Electron trapping ability

PAG-1 PAG-2＜

Why the amount of generated acid was increased as reduction potential of PAG becomes higher?

Ex. 2 ; Increase of electron trapping ability

Reductionpotential

-(Minus)

+(Plus)

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 3 ; Increase of ionization efficiency

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10Normalized Protection ratio

Rel

ativ

e ac

id g

ener

atio

n yi

eld

PHSPolymer-APolymer-BPolymer-CPolymer-E

The highest acid generation yield was obtained with polymerThe highest acid generation yield was obtained with polymer--E.E.

Ionization potential,Molecular size, Hydrophilicity,Protection ratioE-beam exposure

x 1.5~2.0 higher

OH2+OH

OH

O

+

S+CF3S

O

-OO

OH

e-

EUV light

CF3SO

HOO

BELT

Thermalization/ e- stabilization

R

Ionization

X－RHX－R

Normalized protection ratio0

1

2

Rel

ativ

e ac

id g

ener

atio

n yi

eld

EUV light

BELT

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 3 ; Increase of ionization efficiency

Polymer-E Polymer-A

Data courtesy of SeleteSFET, 0.3NA, Annular (0.3 / 0.7)Resist film thickness: 60 nm

Dose to size: 9.1 mJ/cm2

LWR(short range): 6.3 nmResolution: 28 nm

32 nm L/S

Dose to size: 10.6 mJ/cm2

LWR(short range): 5.9 nmResolution: 25 nm

PolymerPolymer--E improved sensitivity (14%), E improved sensitivity (14%), but this was rather smaller than the increase in acid yield (50~but this was rather smaller than the increase in acid yield (50~100%). 100%).

14 % improvement

　

　　　　　　　　　 October 19, 2009


0

0.2

0.4

0.6

0.8

1

1.2

0.1 1 10 100

LD[nm]

∝EL/N

ils

HP=32nm HP=25nm HP=15nm

0.01

0.1

1

10

100

0.1 1 10 100

LD[nm]

∝LW

R*N

ils

HP=30nm HP=20nm HP=15nm

dhDoseLWRLWR dosecorr •

∗=ν_

diff

Ddosecorr MTFNILS

LLWR

•

⎟⎠⎞⎜

⎝⎛

∝

32

_

1

Optimal diffusion length moving toward shorter as narrowing pitcOptimal diffusion length moving toward shorter as narrowing pitch. h.

D. Van Steenwinckel, et al, Proc. SPIE, 5753, 269 (2005). , D. Van Steenwinckel, et al, J. Vac. Sci. Technol. B, 24, 316 (2006).

MTFdiff: Modulation transfer function due to diffusionLd: Diffusion length of acid, p: pitch, d: Resist thickness

Ex. 4 ; Increase of PAG anion size

0.1 1 10 100Ld, nm

0.01

0.1

1

10

100

∝LW

R*N

ILS

0.1 1 10 100Ld, nm

∝E

L/N

ILS

00.2

0.4

0.6

0.8

1.0

1.2

32nmHP25nm

15nm

32nmHP

15nm

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 4 ; Increase of PAG anion size

R

S+R-SO3

-

R

R

PAG-RSize: very small

PAG-BSize: middle

PAG-CSize: large

PAG-ASize: small

X =

Diffusion length of acid was widely controllable by changing Diffusion length of acid was widely controllable by changing PAG anion structures.PAG anion structures.

D: 79.8 nm2/secLd: 1.07 x 103 nm (90sec)

D: 13.0 nm2/secLd: 1.74 x 102 nm (90sec)

D: 3.44 nm2/secLd: 46.2 nm (90sec)

D: 1.01 nm2/secLd: 13.5 nm (90sec)

X-Y-

PAG-RVery small

PAG-ASmall

PAG-BMiddle

PAG-CLarge

　

　　　　　　　　　 October 19, 2009


PAG-R PAG-B PAG-CPAG-A

EL was increased using EL was increased using PAGsPAGs with low diffusion length.with low diffusion length.

E-beam exposure

15 20 25 300

10

20

30

40

Dose to size, μC/cm2, 100 nm L/S

EL,

%, 1

00 n

m L

/S

PAG-R

PAG-A

PAG-B

PAG-C

10E0 10E1 10E2 10E3 10E4Ld, nm, at 90 sec

0

10

20

30

40

EL,

%, 1

00 n

m L

/SPAG-R

PAG-A

PAG-BPAG-C

　

　　　　　　　　　 October 19, 2009


EL, resolution, and LER were improved by using PAGEL, resolution, and LER were improved by using PAG--C.C.ZZ--factor was also improved in the range from 9 % to 51 %.factor was also improved in the range from 9 % to 51 %.

*1 At 32 nm hp, after LBNL dose calibration. *2 Average of 38 nm hp to 30 nm hp. *3 Obtained using below eq.

LBNL MET, 0.3NA, 450 Rot Dipole, σradius0.1 / σoffset0.57Resist film thickness: 50 nm

Z-factor = (Resolution)3 x (LER)2 x (Sensitivity) T. Wallow, et al., Proc. SPIE 6921, 69211F (2008).

Resist Polymer PAG EL (%) Resolution (nm)Sensitivity*1 (mJ/cm2)LER*2 (nm) Z-factor*3

Resist-A Polymer-A PAG-B 17.9 30 10.1 5.2 5.04E-08Resist-B Polymer-A PAG-C 20.8 22 15 3.9 2.48E-08Resist-C Polymer-B PAG-B 13.5 28 10.6 4.2 4.03E-08Resist-D Polymer-B PAG-C 12.3 24 10.4 3.7 2.16E-08Resist-E Polymer-C PAG-B 14.2 28 7.5 5 4.28E-08Resist-F Polymer-C PAG-C 18.1 24 11.3 4.8 3.89E-08

Data courtesy of SEMATEC

　

　　　　　　　　　 October 19, 2009


24nm HP30nm HP 26nm HP28nm HPResist-A, PAG-B

20nm HP22nm HP

Resist-B, PAG-C

Resist-C, PAG-B

Resist-D, PAG-C

Data courtesy of SEMATEC

　

　　　　　　　　　 October 19, 2009


Relation between LER and resolution was improved Relation between LER and resolution was improved by suppressing acid diffusion. by suppressing acid diffusion.

PAG-BPAG-C

TargetTarget

-Y-

-Y-

Further improvement ?Further improvement ?

EUV exposure

0 10 20 30 400

1

2

3

4

5

6LE

R, n

m

1:1 hp resolution, nm

　

　　　　　　　　　 October 19, 2009


TTechnologies to overcome shotechnologies to overcome shot--noise statistics are required !noise statistics are required !

0

1

2

3

4

5

6

0 5 10 15 20

Sensitivity (mJ/cm2)

LER

(nm

)

PAG-B

PAG-C

0

5

10

15

20

25

30

35

0 5 10 15 20

Sensitivity (mJ/cm2)1:

1 hp

Res

olut

ion

(nm

)

PAG-BPAG-C

Clear tradeoff relationships were observed between sensitivity Clear tradeoff relationships were observed between sensitivity and LER, and sensitivity and resolution at hp 3x nm patterning. and LER, and sensitivity and resolution at hp 3x nm patterning.

TargetTargetTargetTarget

1:1

hp re

solu

tion,

nm

0

10

20

30

0 5 10 15 20Dose to size, mJ/cm2

0 5 10 15 20Dose to size, mJ/cm2

0

1

2

3

4

5

6

LER

, nm

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 4 ; Polymer bounded PAG (ultimate short diffusion length)

（50 keV point beam writing, 25 nm L/S）

Control, Polymer - PAG blend type

40 μC/cm238 μC/cm236 μC/cm234 μC/cm232 μC/cm230 μC/cm2

80 μC/cm272 μC/cm264 μC/cm256 μC/cm248 μC/cm240 μC/cm2

110 deg PEB

130 deg PEB

36 μC/cm2 76 μC/cm268 μC/cm260 μC/cm252 μC/cm244 μC/cm2

Polymer bounded PAG

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 4 ; Polymer bounded PAG (ultimate short diffusion length)

（50 keV point beam writing, 30 nm L/S）

Polymer bounded PAG

66.7 μC/cm2

LWR = 2.8 nm30.0 μC/cm2

LWR = 5.4 nm

Control, Polymer - PAG blend type

　

　　　　　　　　　 October 19, 2009


0

1

2

3

4

5

6

0 10 20 30 40 50 60

Dose (mJ/cm2)

LW

R (

nm

)

(1) Base

(2) Photo decomporsable base

0

1

2

3

4

5

6

0 10 20 30 40 50 60

Dose (mJ/cm2)

LW

R (

nm

)

(1) Base

(2) Photo decomporsable base

Photo decomposable quencher could improve the relationship between LWR and sensitivity.

MET@ALS

Ex. 5 ; Effect of photo decomposable quencher

Acid image

[H+](x,z)

Exposed UnexposedInitial acid image

Base[B](x,z)

Acid image

[H+](x,z)

Exposed Unexposed

Photodecomposable

base[B](x,z)

Initial acid image

(1)

(2)0

1

2

3

4

5

6

LWR

, nm

0Dose to size, mJ/cm2

10 20 30 40 50 60

　

　　　　　　　　　 October 19, 2009


Minimization of dissolution unit size

AcidDiffusion Minimization of

molecular size Reduction ofmolecular coagulation

Ex. 6 ; Reduction of polymer molecular weight

　

　　　　　　　　　 October 19, 2009

3. Technologies to improve RLSEx. 6 ; Reduction of polymer molecular weight

LWR improvement by reducing unit sizeLWR improvement by reducing unit size

OH

G. P. Patsis et al., Microelectronic Engineering 75 (2004) 297.

OR OR

RO RO OR OR

Hirayama et al., EUVL symposium 2008.

Approx. 2 nmApprox. 2 nm

Both low Mw polymers and molecular resists Both low Mw polymers and molecular resists can reduce their unit size for LWR reduction.can reduce their unit size for LWR reduction.

a) Polymer resist5

Gyr

atio

n ra

dius

, nm

4

3

2

1

0

Number of polymerized unit0 20 40 60 80 100

b) Molecular resist

　

　　　　　　　　　 October 19, 2009


Reduce polymer Mw to improve LWR Reduce polymer Mw to improve LWR

We have designed four resists to clarify We have designed four resists to clarify if low Mw polymers demonstrate low LWR and improved RLS tradeoffif low Mw polymers demonstrate low LWR and improved RLS tradeoffs.s.

OH O O

Low postLow post--exposure baking temperature and exposure baking temperature and PAG with a bulky anion to suppress acid blurPAG with a bulky anion to suppress acid blur

Drawback: Low Tg?

AcidDiffusion

Y- Y-

　

　　　　　　　　　 October 19, 2009


Lowering of polymer Mw caused a large drop in film Lowering of polymer Mw caused a large drop in film TgTg, , --8080℃℃ ! !

100

110

120130

140

150

160170

180

190

200

High Mw Mid. Mw Low Mw Low Mw + PAG-B

Tg o

f res

ist f

ilm (

゜C

)

- 80 ℃

High Mid. Low Low+ bulky PAG

- 35 ℃

Res

ist f

ilm T

g, o C

1000

150

200

100

110

120130

140

150

160170

180

190

200

High Mw Mid. Mw Low Mw Low Mw + PAG-B

Tg o

f res

ist f

ilm (

゜C

)

- 80 ℃

High Mid. Low Low+ bulky PAG

- 35 ℃

Res

ist f

ilm T

g, o C

1000

150

200

　

　　　　　　　　　 October 19, 2009


Polymer Mw High Middle Low

hp 25nm

hp 32nmTop down

Esize [mJ/cm2]EL [%]LWR [nm]

10.6712.3%10.48

10.2413.8%

7.25

11.0914.5%

7.53

11.2916.8%

8.48

hp 32nmCross section

PAG (Acid)

Resolution limit hp 32nm hp 25nm hp 25 nm

Y- Y-

Res., LWR and EL were changed depending on polymer Mw and PAG. Res., LWR and EL were changed depending on polymer Mw and PAG.

PEBPEB9090℃℃ / 90/ 90secsec(std. 110(std. 110℃℃))

　

　　　　　　　　　 October 19, 2009


0.01

0.1

1 10

35 35 hp 32 hp 30hp 28hp 26hp hp 32 hp 30hp 28hp 26hp

High MwHigh Mw

Mid. MwMid. Mw

Low MwLow Mw

Low Mw Low Mw + bulky PAG+ bulky PAG

High MwHigh Mw

Mid. MwMid. Mw

Low MwLow Mw

High dissolution contrast makes low Mw polymer high resolution. High dissolution contrast makes low Mw polymer high resolution.

Dis

solu

tion

rate

(nm

/sec

)

0.01

Dose, (μC/cm2, 50 eV E-beam)1 10 100

0.1

1

10

100

1000

　

　　　　　　　　　 October 19, 2009


45 hp32 hp

Low Mw polymer did not reduce LWR Low Mw polymer did not reduce LWR

X-sectionsat 32 nm hp

LWR

(nm

)

Molecular weight of polymerHigh

6

5

4

3

2

1

0Middle Low Low

(Bulky PAG)

Ex. 6 ; Reduction of polymer molecular weight

　

　　　　　　　　　 October 19, 2009


0

2

4

6

8

10

12

0 10 20 30

EL of hp 32 nm (%)

Shor

t-ran

ge L

WR

(nm

)0

2

4

6

8

10

12

0 10 20 30

EL of hp 45 nm (%)

Shor

t-ran

ge L

WR

(nm

)

Lower EL, which indicates higher acid diffusion, caused lower LWLower EL, which indicates higher acid diffusion, caused lower LWR, R, indicating EL (resolution) indicating EL (resolution) -- LWR tradeoff. LWR tradeoff.

45 nm hp

High MwHigh Mw Mid. MwMid. Mw Low MwLow Mw

32 nm hpHigh MwHigh Mw

Mid. MwMid. Mw Low MwLow Mw Low Mw +Low Mw +bulky PAGbulky PAG

Low Mw +Low Mw +bulky PAGbulky PAG

Smoothing effectSmoothing effectby acid diffusion?by acid diffusion?S

hort

rang

e LW

R, n

m

0

2

4

6

8

0 10 20 30EL of 45 nm HP, %

0 10 20 30EL of 45 nm HP, %

Sho

rt ra

nge

LWR

, nm

0

2

4

6

8

10

12

　

　　　　　　　　　 October 19, 2009

4. Summary

Today, 25nm HP resolution, 5nm LWR and 12mJ/cm2 sensitivity have been demonstrated, but these are still far behind the target at present.Our design policy to improve RLS further consists of enhancementof aerial image contrast and minimization of dissolution unit size.The enhancement of aerial image contrast could be achieved by the following ways.

Enhance electron and acid generationReduce electron and acid diffusion

Some concrete examples to enhance acid generation and reduce electron and acid diffusion are presented to be effective to improve RLS. Further investigation must be necessary to meet the target.It would be also important to realize minimization of the dissolution unit size.

　

　　　　　　　　　 October 19, 2009

Acknowledgement

Mr. Kawamura and Dr. Itani from Selete Prof. Tagawa and Prof.Kozawa from Osaka University

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