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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.