Kentaro Matsunaga, Hiroaki Oizumi, Koji Kaneyama, Gousuke...

2010 International Symposium on Extreme Ultraviolet Lithography October 18, 2010

EUV resist materials and processing at Selete

Kentaro Matsunaga, Hiroaki Oizumi, Koji Kaneyama, Gousuke Shiraishi, Kazuyuki Matsumaro, Julius Joseph

Santillan and Toshiro Itani


Outline

•Selete’s previous work

•Resist Materials•SSR6, SSR7

•Resist Processes•Ultra thin under layer, Alternative developer, Alternative rinse solution

•Fundamental Studies•Flash PEB, HS-AFM

•Conclusion


Selete’s Previous work (2009-2010)

0%

20%

40%

60%

80%

100%

0.1 1 10 100 1000 10000

length [mm]

Yie

ld [

%]

43 nm hp38 nm hp35 nm hp32 nm hp

Manufacturability test (PL TEG)Selete Standard Resist

Exposure PEB Development RinseResistCoat PAB

Alternative rinse solutions

AlternativedevelopersolutionTBAH

Under-layerN+

HO-

Adhesion

Process evaluation and optimization

Resist baking in vacuum system

PEBin vacuum

PABin vacuum

SSR4 (hp26nm)

Condition: SFET NA0.3, Illum. Annular (0.7/0.3) Thick: 60nm

Pattern collapse

SSR4 SSR5

Update of resist materials and processes in this presentation.


Evaluation Conditions using SFET

Pattern Exposure– Exposure Tool : SFET (EUVA / Canon)

・NA 0.30, Mag. 1/5, ・Annular (σ 0.7/0.3) or X-slit

CD-SEM Condition

Tool ：S-9380Ⅱ(Hitachi)Vacc ：800VIp ：5.0pAMag. ：150ｋFrame ：32

350pixelsMeasurement Point

5-Differential

77Smoothing

Threshold: 50%Method

Auto / Target: 5 / Limit: 3ACD

17pixels16pixelsSum Lines / Point

350pixelsInspection Area

LWRLine WidthItem

SEM Measurement Condition

Calculation of Illumination Contrast

Ref: Y.Tanaka EUVL Symposium 2010 (ET-P05)

with aberration & flare

Half Pitch (nm)

Imag

e Co

ntra

st

X-slit

V line

Annular(σ=0.3/0.7)


Resist materials6th Selete Standard Resist (SSR6)7th Selete Standard Resist (SSR7)


2010 Update of Selete Standard Resists

2.4×1016

16.3

7.5

26

10.7

SSR5

4.2×1016

17.5

5.5

28

12.4

SSR4

9.312.013.412.2-EL(%)

@hp32nm

Top-down SEM(hp32nm)

1.2×1016

5.7

28

18.1

SSR7

2.5×1016

5.7

24

14.6

SSR6

Cross-section SEM(hp32nm)

2.0×10161.8×10162.8×1016Out-gassing(moles./cm2/s)

6.710.37.6

@45nmL/SLWR (nm)@hp32nm

252840Resolution(nm L/S)

13.117.413.4@

45nmL/SDose (mJ/cm2)

@hp32nm

SSR3SSR2SSR1Resist name

45nmL/S

Exp. Tool :SFETNA0.3, Annular (0.7/0.3)Resist Thick. 50 or 60nm

Newly released!!

Polymer Molecular


Imaging performance of SSR6hp32nm hp28nm hp26nm hp24nm hp22nm

SFET NA=0.3Thick=50nmDeveloper: 2.38% TMAH22nm L/S pattern was resolved using TMAH Developer.

Sensitivity was less than 15mJ/cm2.LWR was 5.7nm at hp32nm.

Annular(0.7/0.3)

Thick. : 50nm

Annular

hp20nm

X-slit

X-slit

hp32nm using Annular illuminationDose: 14.6mJ/cm2

LWR: 5.7nmExposure Latitude: 12%


hp15nmhp16nmhp22nm

X-dipole

Exposure Tool: SFETResist: SSR6 (Thick:40 nm)Dev: TMAHCD-SEM: CG-4000

Using x-dipole illumination, modulation was formed even at 15 nm L/S pattern.

Ultimate resolution of SSR6hp18nm

with aberration & flare

Annular(σ=0.3/0.7)

X-dipole

V line

Half Pitch (nm)

Imag

e Co

ntra

st


Requirement to 1x-nm lithography

•Resolution : <1x nm•LWR: <1.xnm

High-Mw

Ultra thin resist thickness

Pattern collapse

Low-Mw

•Prevention of pattern collapse Thinner resist thickness Strong etching durability

RRR RRMe

•Low molecular weight (MW)•Strong etching durability

Fullerene based resistEtching durabilityDry-etcher: U-8150 (Hitachi)Etching :Cl2, 0.4Pa, 500W

Nor

mal

ized

etc

hing

rate

0

0.2

0.4

0.6

0.8

1

1.2

ArF resist(dry)

SMR377 (PHS-tBOC)

MET-2D SMR567(Fullerene)

1.000.81

0.370.53


Imaging performance of SSR7hp32nm hp28nm hp26nm hp24nm hp23nm

hp32nm using Annular illuminationDose: 18.1mJ/cm2

LWR: 5.7nmExposure Latitude: 9.2%

Annular(0.7/0.3)

Thick. : 60nm

Annularhp22nm

X-slit

X-slit

Thick. : 45nmhp24nm pattern was resolved with x-slit illumination.Sensitivity was 18.1mJ/cm2 at hp32nm.LWR was 5.7nm at hp32nm.


22nm Targets: Esize : 10mJ/cm2

Short-range LWR : hp x 10%

Significant improvement is necessary to reduce LWR by process.

Lithography performance of Newly SSR’s

10

20

25

35

5 10 15 20

Sensitivity – Ultimate Resolution

Res

olut

ion

limit

(nm

)

SSR3

SSR2

Esize of hp32nm (mJ/cm2)

SSR4

SSR5

15

30

SSR6

SSR7

0

2.5

5.0

7.5

10.0

12.5

5 10 15 20

Sensitivity - LWR

Shor

t-ran

ge L

WR

: 3σ

(nm

)at

hp3

2nm

Esize of hp32nm (mJ/cm2)

SSR3

SSR2

SSR4

SSR5

SSR6 SSR7

First molecular

resist

First molecular

resist

SFET NA0.3Annular Illum.


Resist Processes• Ultra thin under layer• Alternative developer solution• Alternative rinse solution


Alternative resist processes


Alternativerinse

solutions

Alternative developersolution

Ultra thin under-layer

AdhesionProcessflow


3x-nm TEG Resist SSR3 80nm thick.

UL 20nm thick.

Substrate

Hard mask (HM)

Ultra thin under layer (UL) for 2x-nm TEG

Patternprofile on UL

UL Coating on HM

Optical View(Dark Field)

No Pin hole

Standard UL20nm thick

hp32nm

Diluted UL<10nm thick

EBR

Pin hole

Optimized solvent<10nm thick

2x-nm TEG Resist SSR4<60nm thick.

UL <10nm thick.

Anti-reflective performance is not required in EUV exp.

No Pin hole

EBR

SEM View

Nano-sized pinhole

2um

Optimized polymer<10nm thick

Ultra thin UL was coated on hard mask layer without nano-sized-pinhole.

No nano-sized pinhole

No Pin hole

EBR

hp24nm


0.26N TMAH

Developer

N+

HO-

NMD-FX(0.26N TBAH+additive)

N+HO-

Tetrabutyl ammonium hydroxide

Alternative developers solutionshp28nm hp26nm hp24nmhp32nm

SFET NA0.3Resist : SSR450nm Thick.

X-slit

Pattern collapse was improved with NMD-FX(TBAH solution).


8.4

8.4

8.6

hp24nm

11.2mJ/cm2

TBAH

8.4

8.5

8.6

hp24nm

11.5mJ/cm2

TMAH

SSR5SSR5

15.5mJ/cm214.8mJ/cm211.9mJ/cm212.4mJ/cm214.8mJ/cm212.8mJ/cm2Exposure Dose

6.06.06.16.47.58.8

hp 26nmLWR [nm]

6.3

5.5

hp22nm

TMAH

SSR6SSR6

---

7.7

hp26nm

TMAH

SSR4SSR4

6.8

5.8

hp22nm

TBAH

6.8

7.2

hp24nm

TBAH

8.28.5

hp 24nmLWR[nm]

8.18.5

hp 28nmLWR [nm]

hp25nmhp24nmUltimateResolution

TBAHTMAHDeveloper

SSR3SSR3

Lithography performance of SSR’s using TMAH and TBAH

SSR3 : LWR was improved with TBAH. (about 8%)SSR4 : Pattern collapse was improved with TBAH.SSR5 : Lithography performance was stable on both developer.SSR6 : Sensitivity was lower using TBAH.It is necessary to match the developer to the resist material.


Prevention of pattern collapse using alternative rinse solution

Reference(D.I.W.)

hp [nm] 28nm30nm32nm35nm40nm

Evaluation condition・EXP tool :SFET NA0.3 Annular・Resist : SSR4 (Thickness:80nm)・Developer : TMAH 2.38wt%

26nm

: collapsed : not collapsed

Rinse K

Rinse N

Pattern collapse was prevented using alternative rinse solution


TMAH(Reference)

hp [nm]

TBAH &Rinse N

TBAH

Evaluation condition・EXP tool :SFET NA0.3 Annular・Resist : SSR4(Thickness 80nm)

: collapsed: not collapsed

Prevention of pattern collapse using alternative rinse & developer

"Combination process of TBAH & rinse N” achieved 26nm L/S with 80nm film thickness.

28nm30nm32nm35nm40nm 26nm

TMAH &Rinse N


Fundamental Studies• Flash PEB • In situ dissolution analysis


Fundamental Studies


Alternativerinse

solutions

Alternative developersolution

Ultra thin under-layer

AdhesionProcessflow

Flash PEB

In situ dissolution analysis


Fundamental Studies• Flash PEB • In situ dissolution analysis


Flash PEB Process System

Flash PEB Process ConditionsSource : Xe lampWavelength : >300nm

Energy : ~ 30J/cm2

Process time : < 10msec

Wave length [nm]

Inte

nsi

ty [

%]

Reference: USHIO Web site

Xe lamp spectral distribution

Stage

Wafer

Window

Light source（Xe lamp)

Power supply

Detailed description of Flash PEB process system

Reference Submillisecond post-exposure bake of chemically amplified resists by CO2 laser heat treatment,

Byungki Jung et.al, Proc.SPIE Vol.7639, 76390L


Acid diffusion length

Shorter acid diffusion length was confirmed using the Flash PEB process.•Due to very short PEB time (~1ms).

Resist: SSR5Diffusion length = sqrt (2*D*t)D: Diffusion coefficient [nm2/s]t: PEB time [s]

SiAcid detector layer

Acid source layer

hv = 193nm

Coat +

Exposure

Flash PEBor

Hot plate PEB

Acid diffusion

Development

Film loss

Experimental flow

60nmt

300nmt

off-line off-line FT Measurement

Hot plate PEB process

0

10

20

30

40

50

110 115 120 125 130Hot plate temp. [ºc]

Diff

usio

n le

ngth

[nm]

PEB time: 60s

Flash PEB process

0

10

20

30

40

50

0 5 10 15 20 25Flash energy [J/cm2]

Diff

usio

n le

ngth

[nm]

PEB time: 1ms

Results


6.05.44.9LWR [nm]

15.014.014.0Esize [mJ/cm2]

Hot plate(100ºc90s)

Flash PEB(15.3J/cm2)

PEB process

11.0

5.7

hp50nm

6.15.3LWR [nm]

10.0

hp60nm

11.5Esize [mJ/cm2]

SEM Image

SEM Image

hp45nm

Lithographic Performance (Initial Result)

• Initial imaging performance was successfully obtained with flash PEB process.• No significant effect on LWR and slight deterioration of Esize.

SFET NA=0.3Annular IlluminationResist SSR5, 60nm


Fundamental Studies• Flash PEB• In situ dissolution analysis


Factors

Analysis of dissolution characteristics

0

20

40

60

80

100

0 10 20 30Development time　[s]

Film

thick

ness

[nm

]

Thickness of swelling layer∼ 7.6 nm

0

0.8 E0

1.2 E0 @ Oska Univ,

1.0 E01.1 E0

1.4 E0

~ 0.9 E0 Selete

0

20

40

60

80

100

0 10 20 30Development time　[s]

Film

thick

ness

[nm

]

Thickness of swelling layer∼ 7.6 nm

0

0.8 E0

1.2 E0 @ Oska Univ,

1.0 E01.1 E0

1.4 E0

~ 0.9 E0 Selete

Molecular resist0

20

40

60

80

100

0 1 2 3 4 5 6Exposure dose [mJ/cm2]

Film

thick

ness

[nm

] Polymer resist

0

20

40

60

80

100


Film

thick

ness

[nm

]

0

20

40

60

80

100


Film

thick

ness

[nm

] Polymer resist

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

0.1 1 10Normalized dose from E0

Dis

solu

tion

rate

[nm

·s-1

]

TMAHTPAHTBAH

Dissolution rate monitor Quartz crystal microbalanceSensitivity curves

•No direct visual evidence of the actual dissolution process has been presented.•High speed atomic force microscopy (HS-AFM) has potential in in situ dissolution characterization.

Developer •Ultimate resolution•LWR•Pattern collapse

•Aspect ratio• Defectivity

•Micro bridge, scum , blob

Dissolution characteristics

Swelling


HS-AFM measurement system & procedure

“Cantilever assembly”

“Sample assembly”SampleWafer

“Cantilever assembly”

“Sample assembly”SampleWafer

3. Start measurementHigh speed scanning

4. In situ measurementInject developer solution

1. Assemble sample wafer

2. Inject D.I. WaterHS-AFM system

Measurement area


2D HS-AFM 3D HS-AFM

TMAH

TBAH

32nm I/L pattern - 2D & 3D video

Measurement of TMAH and TBAH developer

SSR4 (hp26nm)

Resist: SSR4


2D HS-AFM 3D HS-AFM

32nm I/L pattern - 2D & 3D video

Measurement of polymer and molecular resist

置き換え置き換え

SSR7(Molecular

resist)

SSR6(Polymerresist)


Conclusion

•Resist Materials•SSR6 and SSR7 were released for manufacturability evaluation.•SSR6 was resolved 22nm L/S pattern using TMAH developer•SSR7 was the first molecular resist for manufacturability evaluation in Selete.

•Resist Processes• Ultra thin under layer was successfully coated without nano-sized pinhole.• NMD-FX developer (without freeze issue) improved pattern collapse of SSR4.• Alternative rinse solution improved pattern collapse.

•Fundamental Studies• EUV Resist patterning was initially demonstrated using Flash PEB• In situ dissolution characteristics was analyzed using the HS-AFM.


A part of this work is supported by New Energy and Industrial Technology Development Organization (NEDO).

Selete member companies (EUV Litho-mask program).

Resist and material suppliers.

Acknowledgements


Related posters in this Symposium

•Fullerene resist (RE-P07)

•Rinse solutions (RE-P11)

•Flash PEB (RE-P10)

•In situ dissolution analysis (RE-P09)

•Resist outgassing (RE-P08)

••Resolution capability of SFET Resolution capability of SFET (ET-P05)

Kentaro Matsunaga, Hiroaki Oizumi, Koji Kaneyama, Gousuke...

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