Accuracy of the ASET Dilatometer for Low Thermal Expansion

EUVEUV LITHOGRAPHYLITHOGRAPHY2006 EUVL Symposium, 16-18 October 2006ASET, Takeichi 1

Accuracy of the ASET Dilatometer for Low Thermal Expansion Materials

Yoshimasa Takeichi, Iwao Nishiyama Association of Super-Advanced Electronics Technologies

(ASET)EUV Process Technology Research Laboratory

Naofumi YamadaNational Institute of Advanced Industrial Science and Technology

(AIST) National Metrology Institute of Japan

（NMIJ）

EUVEUV LITHOGRAPHYLITHOGRAPHY2ASET, Takeichi 2006 EUVL Symposium, 16-18 October 2006

Acknowledgement

This work was supported by the New Energy and

Industrial Technology Development Organization

(NEDO).


Outline

1. Background

2. Methodology Principle & design of the dilatometer

3. Results Performance of the dilatometer

Repeatability, Resetability, Accuracy

4. Status of user use

5. Summary


1. Background





5. Summary


（Change in substrate temperature）

Exposure

Before After

Expansion(Shrinkage)

Background (1): CTE Requirement

Mask ｓtage

source

λ:13nm

Waferstage

Illumination Optics

Projection Optics λ：13.5 nm

Reflective Optics

ML,Reflectance :<70%)

Exposure under vacuum

Exposure deforms mask.

Configuration of EUVL system

CTE: Coefficient of Thermal Expansion

Difficult requirement to meet

No commercial dilatometer that meets EUVL requirements

Obstacle to the development of LTEMs

SEMI standards (Class A)0±5 ppb/ﾟC（19-25ﾟC）1ppb = 0.1nm (@10cm)

Strong demand for a metrology that meet EUVL

requirement


Background (2): CTE Metrology Development Project

Metrology andpatent ownership

EUVL technologyLTEM developer

Metrology user

Research organizationsLTEM suppliers

DevelopmentDevelopmentteamteam

Equipment supplierEquipment supplierOptical heterodyne interferometer,

Thermal control technique

SpecificationsPerformance

evaluation

Manufacture of equipment

Equipment design


Background (3): Goal and Targets

Overall Goal• To establish a CTE metrology tailored to meet EUVL

requirements and help bring EUVL closer to the stage of practical use

Target

• Resolution: 1 ppb/ﾟC or less

• Repeatability(σ): 1 ppb/ﾟC or less


1. Background

2. Methodology Principle & design of the

dilatometer




5. Summary


AOM

AOM

APD1

He-Ne laser

Spec

imen

Reflector

PBS

Referencelight

Measurementlight

Light frequency 1

Light frequency 2

APD2

Change in length due to change in temperature

Vacuum chamber

Ther

mal

con

trol b

lock

Ther

mal

con

trol b

lock

AOM

AOM

APD1

He-Ne laser

Spec

imen

Reflector

PBS

Referencelight

Measurementlight

Light frequency 1

Light frequency 2

APD2

Change in length due to change in temperature

Vacuum chamber

Ther

mal

con

trol b

lock

Ther

mal

con

trol b

lock

Phase difference between APD1 and APD2 at T1：（ φAPD2 -φAPD1）T1

Phase difference between APD1 and APD2 at T2：（ φAPD2 -φAPD1 ）T2

( )λπφφ L

APDAPDΔ

=−Δ2

12

Change in phase difference between T1 and T2：

Methodology (1): Principle of Measurement

ΔL：Change in length

(Quadruple - sensitivity)

Optical heterodyne interferometry

Intensity of superimposed light

Electric field intensity

( )1111 2cos φπ += tfaE

( )2222 2cos φπ += tfaE

221 EEI +=

{ }φπ Δ+++

= tfaaaab2cos2

2 21

22

21

( ) ( ){ }212121

22

21 2cos2

2φφπ −+−+

+= tffaaaa


Methodology (2): CTE Calculation

Determination of sample length

Determination of change in sample length due to thermal expansion

Stability of thermo control and determination of temperature

This term has a large influence.

This term has little influence.

This term has little influence.

Consideration of error factors

TLLCTE

Δ⋅

Δ=

1

0

( ) ( ) αδδαδδαTLsp

total TT

TLL

LL

⎥⎦⎤

⎢⎣⎡ΔΔ

+Δ⎥

⎦

⎤⎢⎣

⎡ Δ+⎟⎟

⎠

⎞⎜⎜⎝

⎛=

1

00

0 α：low

Δ Ｔ

Δ L

L0 L


Methodology (3): ASET’s DilatometerEquipment supplier:CTE-01

Thermal-shield

Stone plateVibration isolation table

interferometer

Frame

Water

sample

LTEM

Inver

Peltier device

Structure of dilatometer

Pertier Device

Con

stan

t tem

pare

ture

blo

ck

radiation radiation

conduction

Con

stan

t tem

pare

ture

blo

ck

conduction

Reference

Sample


Methodology (4): Example of Data Ti-doped silica glass

13.2

0

-13.2 Cha

nge

in S

ampl

e Le

ngth

[ nm

]

18

20

22

24

26

0 10 20 30 40 50 60 70 80 90 100 110 120

Time [hr]

Avg

. tem

pera

ture

[ ℃]

ΔT

-30

-20

-10

0

10

20

30

0 10 20 30 40 50 60 70 80 90 100 110 120

Time [hr]

Phas

e diff

eren

ce [d

eg.]

ΔΦ＝ΔL

Change in phase difference

TLLCTE

Δ⋅

Δ=

1

0

Change in sample temperature


1. Background





5. Summary


Results (1): Evaluation Items

• ReproducibilityRepeatability (Static) : Reproducibility obtainable from measurements of the same sample without moving it .Resetability (Dynamic) : Reproducibility obtainable from measurements involves changing the sample

• AccuracyComparison with AIST’s measurements


Results (2): Reproducibility of Measurements

-20-10

01020304050

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102

Time [hr]

Phas

e D

iffer

ence

[de

g]

(a)

18.0

20.0

22.0

24.0

26.0

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102

Time [hr]

Tem

para

ture

(Ave

rage

) [ ℃

] (b)Change in sample temperature

Change in phase difference

a

a

ResetabilityΔCTE: ±0.85 ppb/°C

Repeatabilityσ: 0.80 ppb/°C


Fig. The high precision CTEmeasurement equipment at AIST.

Results (3): AIST’s Dilatometer


[ ppb/ ℃]

Sample ASET AISTExpanded

Uncert aint y(AIST)

Difference(ASET - AIST) Remarks

Quart z 460.3 461.3 2.3 -1.0 18-22 C゚, Δ T：4 C゚

LTEM-A 2.0 2.3 1.2 -0.3 19-25 C゚, Δ T：6 C゚

LTEM-B 8.3 9.6 1.1 -1.3 19-25 C゚, Δ T：6 C゚

Results (4): Accuracy of Measurements

Table. Comparison with AIST Measurement.

The differences are in the AIST’s uncertainty range. We’ve verified the accuracy of the ASET’s dilatometer.


Results (5): Summary of the evaluation results

Table. Summary of the evaluation results for the dilatometer.

Target Result s Evaluat ion

Resolut ion (10-cm-long specimen) ＜1 ppb/ ℃ ＜0.35 ppb/ ℃ Good

Reproducibilit y St at ic (σ ) ＜1 ppb/ ℃ ＜0.80 ppb/ ℃ Good

Reset abilit y (Δ CTE) ------- ＜± 0.85 ppb/ ℃ Good

Accuracy Comparison wit h AIST ------- ＜1.3 ppb/ ℃ Good

Evaluat ion It ems

(wit hin t he expanded uncert aint y)


1. Background





5. Summary


User use (1): Asahi Glass Co., Ltd.AGC has been developing

Low Thermal Expansion Material for EUVL substrate.Material : AZ (TiO2-SiO2 glass)Target of CTE property: 0+/- 5 ppb/oC (at 19-25oC)

-60

-40

-20

0

20

40

60

CTE

at 2

2oC

[ppb

/o C]

TiO2 conc. [wt%]

Fig.: Dependence of CTEon TiO2 conc. in AGC’s LTEM

AGC had investigated the dependence of CTE on TiO2 conc. in their LTEM using ASET’s dilatometer and they demonstrated the CTE at 22oC is in proportion to TiO2 concentration.

The CTE can be optimized to 0+/-5 ppb/oC by the relationship between the CTE and TiO2 conc.

Poster SessionDevelopment of Low Thermal Expansion Material and CTE measurement tool for EUVL


User use (2): TOSHIBA CERAMICS CO., LTD.

T/C’s LTEM Product Development Target (6025 Sub. material)Mean CTE : ±5ppb/deg KCTE Spatial Variation : ＋6ppb/deg K

Now in Development

Static Measurement Stability

Change in Phase difference :Δθ=0.2°(Fig.1 red circle)

Equipment resolution isgood enough forLTEM CTE measurement!!

0 6 12 18 24 30 36 42 48 54

Phas

e D

iffer

ence

[de

g]

Fig. Change in phase differencetime [hrs]


User use (3): NIHON CERATEC CO., LTD.MaterialZPF (Zero thermal expansion Pore Free ceramics)Feature ：①Low thermal expansion, ②High stiffness(150GPa), ③Pore

FreeApplication：Parts for equipments of LSI manufacturing (Mirror, Chuck, etc)Measured Data Result

(1)23 to 25 ℃

14ppb/ ℃

(2)21 to 23 ℃-14ppb/ ℃18

192021222324252627

1 501 1001 1501 2001 2501 3001- 18- 16- 14- 12- 10- 8- 6- 4- 20

Data Point

Tem

pera

ture

/ ℃

⊿L /

nm

(Sample Length : 100.0 mm)

⊿(⊿L)


1. Background





5. Summary


Summary・ An optical heterodyne interferometric dilatometer (CTE-01)

tailored to meet EUVL requirements has been developed. ・ Reproducibility of data

Repeatability, σ:<1ppb/°C, Resetability, ΔCTE:<±1ppb/°CThese values meet the target specifications.

・ Accuracy of dataThe differences are in the AIST’s uncertainty range.

We’e verified the accuracy of the ASET’s dilatometer.・ LTEM supplier have started CTE evaluation by ASET’s

dilatometer.・ The CTE-01 will be commercialized from next year. We

confirm that ｉｔ will accelerate LTEM development.

Documents

Accuracy of the ASET Dilatometer for Low Thermal Expansion