SiUE VCornellIntel

SiUE VCornellIntel

Absorbance Measurement of Polymers Absorbance Measurement of Polymers at EUV Wavelength: Correlation between at EUV Wavelength: Correlation between

Experimental and Theoretical Experimental and Theoretical CalculationsCalculations

Young-Je Kwark, J. Pablo Bravo, and Christopher K. OberMaterials Science and Engineering, Cornell University

Manish Chandhok, Heidi Cao, and Hai DengIntel Corporation

Eric GulliksonLawrence Berkeley Laboratory

SiUE VCornellIntel

SiUE VCornellIntel

Requirements for EUV ResistsRequirements for EUV ResistsIntel targets for insertion of EUV tools into

manufacturing in 2009

2009Resolution – Gate (nm) 15

Resolution – ½ pitch (nm) 45LWR - 3σ (nm) 1.5

Sensitivity (mJ/cm2) 2-5Absorbance (Absorbance (µµmm--11)) LowLow

Depth of Focus (µm) > 0.2Outgassing No outgassing

Collapse No collapse

Cao, Heidi, et al., Proceeding of SPIE 2003, 5039, 484.

SiUE VCornellIntel

SiUE VCornellIntel

Is Absorbance Important in EUVL?Is Absorbance Important in EUVL?

Reducing absorbance increases resolution and wall angle.

18

20

22

24

26

28

30

32

1 2 3 4 5

Absorbance (µm-1)

CD

(nm

)80

81

82

83

84

85

86

87

88

89

90

Ang

le (°

)Smaller absorbance1 5 (µm-1)

Distance (µm)

Res

ist H

eigh

t (µm

)

Beta tool (NA=0.25, sigma=0.5) Resist thk = 60 nm, Dose = 2.95 mJ/cm2

0.231 0.238 0.245 0.253 0.260 0.268

0.000

0.012

0.024

0.036

0.048

0.060

Cao, Heidi, et al., Proceeding of SPIE 2003, 5039, 484.

SiUE VCornellIntel

SiUE VCornellIntel

Absorbance in EUV RegionAbsorbance in EUV Region

Absorption at 13.4 nm depends only onchemical composition and density of the material

O

Si

SiUE VCornellIntel

SiUE VCornellIntel

CornellCornell’’s EUV Resistss EUV Resists

BBB

B

BB

CBBB

C

B

H

OO

O OH

OO

OO

lSiCH3

SiCH3

n m

R

SiCH3

nO

O

mSi

OO

OHR

R =O

Si OHO

OO

Hydroxystyrene-based Resists

Si RO

O

R = acid, alcohol, or anhydride

Norbornene-based Resists

Polysilane-based Resists

Boron-containing Resists

SiUE VCornellIntel

SiUE VCornellIntel

Reference PolymersReference PolymersName Structure Preparation M n PDI

poly(methyl methacrylate) (PMMA) Aldrich 18,100 1.68

polynorbornene (PNB) [Pd]

polystyrene (PSt) Aldrich 13,700 1.05

poly(hydroxy styrene) (PHOSt) AIBN 3,600 1.46

poly(trimethylsilyl styrene) (PTMSSt) AIBN 13,000 1.68

poly(methylphenyl silane) (PMPS) Gelest 11,100 2.56

poly(phenylsilsesquioxane) (PPSSQ) Gelest 860 2.38

157 nm resist (PAF) AIBN 1,500 6.66

not determined

OO

Si

SiPh

OO Si

Ph

OSi SiPh

OPh

OO

F3C CF3

F3C CF3OH

OH

Si

SiUE VCornellIntel

SiUE VCornellIntel

Theoretical Calculation of AbsorbanceTheoretical Calculation of Absorbance

22 frea ×λ××=σAtomic photoabsorption cross section (σa)

Where, re, classical electron radiusλ, wavelength of X-rayf2, imaginary part of atomic scattering factor

∑∑ =σρ

=µi

iii

aiiA AxMWx

MWN

Linear absorption coefficient of compound (µ)

Where, ρ, densityxi, number fraction of component iAi, atomic weight of component i

http://www-cxro.lbl.gov/optical_constants/

SiUE VCornellIntel

SiUE VCornellIntel

Measurement of Polymer DensityMeasurement of Polymer Density

tRww )(density 2

01

π−

=ρ

t ; measured by profilometer

polymer solution

W0R

spin coating

W1

Literature value

Measured value

Difference (%)

PMMA 1.18 1.28 9PS 1.05 1.22 16

SiUE VCornellIntel

SiUE VCornellIntel

Calculated AbsorbanceCalculated Absorbance

Name Structure Formula Si (wt %)Density (g/cm3)

Linear absorption coefficient (µm-1)

PMMA C5H8O2 0 1.18 5.19

PNB C7H10 0 0.92 2.55

PSt C8H8 0 1.05 2.95

PHOSt C8H8O 0 1.16 4.05

PTMSSt C11H16Si 15 1.14 2.78

PMPS C7H8Si 23 1.12 2.60

PPSSQ C24H20Si4O4 23 1.50 4.52

PAF C15H14O3F12 0 1* 6.97

OO

Si

SiPh

OO Si

Ph

OSi SiPh

OPh

OO

F3C CF3

F3C CF3OH

OH

Si

* Density not determined.

SiUE VCornellIntel

SiUE VCornellIntel

Calculated AbsorbanceCalculated Absorbance

Name Structure Formula Si (wt %)Density (g/cm3)

Linear absorption coefficient (µm-1)

PNB C7H10 0 0.92 2.55

PMPS C7H8Si 23 1.12 2.60

PTMSSt C11H16Si 15 1.14 2.78

PSt C8H8 0 1.05 2.95

PHOSt C8H8O 0 1.16 4.05

PPSSQ C24H20Si4O4 23 1.50 4.52

PMMA C5H8O2 0 1.18 5.19

PAF C15H14O3F12 0 1* 6.97

OO

Si

SiPh

OO Si

Ph

OSi SiPh

OPh

OO

F3C CF3

F3C CF3OH

OH

Si

* Density not determined.

SiUE VCornellIntel

SiUE VCornellIntel

Absorbance Measurement MethodologyAbsorbance Measurement MethodologyGrazing Angle Incidence

Si wafer coated with polymer

detectorsource

θ θ

λ

Fresnel reflectivity equations Refractive indexn = 1 - δ + iβ2

22

22

scossincossinR

θθθθ

−+

−−=

nn

⎟⎠⎞

⎜⎝⎛

πµλ

=β4

µ ; linear absorption coefficient

SiUE VCornellIntel

SiUE VCornellIntel

Determination of absorbanceDetermination of absorbance

03.54=β×

λπ

=Absorbance

Extracting absorbance values:Data is fit by varying β, and δ to a least-squares fitting algorithm.

Best fit of the data gives imaginary part of refractive index (β) as 0.0054.

0 5 10 15 20 250.0

0.2

0.4

0.6

0.8

1.0 PMMAδ = 0.0242β = 0.0054

PMMAδ = 0.0242β = 0.0054

Ref

lect

ance

Angle (deg)

Repeatability of the measurement < 1%Repeatability of the measurement < 1% G-NumberRR®®

11

Techniques for directly Techniques for directly measuring the absorbance measuring the absorbance

of of photoresistsphotoresists at EUV at EUV wavelengthswavelengths

Manish Manish ChandhokChandhok,,aa Heidi Heidi CaoCao,,aa Wang Wang YuehYueh,,aa

Eric Eric GulliksonGullikson,,bb Robert Robert BrainardBrainard,,cc

Stewart Stewart RobertsonRobertsoncc

a Intel Corporation, Hillsboro, OR 97124a Intel Corporation, Hillsboro, OR 97124b Lawrence Berkeley National Laboratory, Berkeley CAb Lawrence Berkeley National Laboratory, Berkeley CA

c Shipley Company, Marlborough, MA c Shipley Company, Marlborough, MA

1 October, 20031 October, 2003Acknowledgements: E. Lin (NIST), G. Zhang (Intel)

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SiUE VCornellIntel

SiUE VCornellIntel

Experimental Data of AbsorbanceExperimental Data of AbsorbanceName Structure Formula

Density (g/cm3)

Calculated µ (µm-1)

Measured µ (µm-1)

D (%)

PMMA C5H8O2 1.18 5.19 5.03 3.1

PNB C7H10 0.92 2.55 2.58 -1.2

PSt C8H8 1.05 2.95 2.70 8.5

PHOSt C8H8O 1.16 4.05 3.88 4.2

PTMSSt C11H16Si 1.01 2.47 2.14 13.4

PMPS C7H8Si 1.12 2.60 2.82 -8.5

PPSSQ C24H20Si4O4 1.50 4.52 4.45 1.5

PAF C15H14O3F12 1* 6.97 10.75 -54.2

OO

Si

SiPh

OO Si

Ph

OSi SiPh

OPh O

OF3C CF3

F3C CF3OH

OH

Si

Difference (D) = (µcalc-µexp)/µcalc × 100 (%)* Density not determined.

SiUE VCornellIntel

SiUE VCornellIntel

Calculation vs. ExperimentCalculation vs. Experiment

0

1

2

3

4

5

6

0 2 4 6µexperimental

µ cal

cula

ted

Name Structure Measured density

Calculated density

PMMA 1.18 1.14

PNB 0.92 0.94

PSt 1.05 0.96

PHOSt 1.16 1.14

PTMSSt 1.01 0.88

PMPS 1.12 1.13

PPSSQ 1.50 1.48

PAF 1.54

OO

Si

SiPh

OO Si

Ph

OSi SiPh

OPh O

OF3C CF3

F3C CF3OH

OH

Si

SiUE VCornellIntel

SiUE VCornellIntel

Effect of ComponentsEffect of Components

0

1

2

3

4

5

6

0 10 20 30 40

Si wt %µ

0

2

4

6

8

10

12

0 20 40 60

O wt %

µcalculation experimentO

OF3C CF3

F3C CF3OH

Si

Si

OO

SiPh

OO Si

Ph

OSi SiPh

OPh

SiPh

OO Si

Ph

OSi SiPh

OPh

•• In general, absorbance increases with increasing oxygen In general, absorbance increases with increasing oxygen content.content.

•• Effect of silicon content is not clear.Effect of silicon content is not clear.

SiUE VCornellIntel

SiUE VCornellIntel

SummarySummary

Absorbance of various polymers in EUV region (13.5 nm) were determined using the grazing incidence method.The measured absorbance values match well with the calculated values. Precise measurement of the density is required to calculate meaningful absorbance values.In general, absorbance increases linearly with increasing oxygencontent. Effect of silicon content is not clear.Repeated measurement of absorbance will be performed using wider variety of polymers.

SiUE VCornellIntel

SiUE VCornellIntel

ACKNOWLEDGEMENTSACKNOWLEDGEMENTS

Cornell UniversityCornell Nanofabrication Facility

Junyan Dai

Intel

Lawrence Berkeley LaboratoryAndy Aquila