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Using resonant soft X-ray scattering to image patterns on undeveloped resists
Guillaume Freychet, I. Cordova, D. Kumar, T. McAfee, C. Anderson, P. Naulleau, C. Wang and Alexander Hexemer
June, 14th 2018
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Context for the semi-conductor industry
With the size reduction of the objects, any sub-nm defects will impact strongly
the performance of the device
1D array : Line gratings
Sub-nm resolution
✓ Pitch✓ Linewidth✓ Line height✓ Roughness✓ Sidewall angle
Parameters to control :
H𝜷
𝝎0
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Small Angle X-ray Scattering (SAXS)
✓Probe electronic density contrast
✓Small angle scattering: probe 1-1000 nm
q =2p
lsin2q
H
qxz (nm-1)
qy
(nm
-1)
2𝞱φ
z
y
x
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Small Angle x-ray scattering (SAXS) on line gratings
Distorted Wave Born Approximation
H
qxz (nm-1)q
y(n
m-1
)2𝞱φ
z
y
x
2𝞱𝜶f
qp
er(n
m-1
)
qpar (nm-1)
xz
y
φ
Grazing-incidence SAXS (GISAXS)
✓ Small incidence angle < 0.2 deg✓ Probe thin films on Silicon wafer (700 μm)
✓ Transmission configuration✓ High energy x-ray source
44
D. F. Sunday et al., ACS Appl. Mater. Interfaces (2017)
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Ewald sphere
Sample surface
Rods coming from the grating
2𝞱𝜶f
qp
er(n
m-1
)
qpar (nm-1)
xz
y
φ
1
2
3
4
56
qper(nm-1)
Inte
nsi
ty (
a. u
.)
6.0
4.0
3.0
2.0
1.0
5.0
7.0
0.5 0.7 0.8 0.90.6
1
2
3
4
5
6
b)
Fitted profileTEM profile
Rotation of the gratings(along z)
1D vertical cut
Critical-Dimension GISAXS
Fit using genetic algorithm
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Resonant Soft X-Ray Scattering (RSoXS)
Small Angle X-Ray Scattering
Electronic density:|δ2 + β2|
Credit: Guinnier A. et al, Ann Phys, 1939, 12:161–237
X-Ray Beam
X-Ray Absorption
Credit: Wanli Yang, ALS
1s
2s
2p
Tunable photon
XRD
Reconstruction of a latent image (before removal of the exposed resist)
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Credit: C. Wang et al, Nano Lett., 2011, 11, 3906
Triblock copolymer:
β
δ
Electronic density|δ2 + β2|
280 eV 284 eV
✓ Tune the energy to enhance the scattering contrast
✓ Before the absorption edge to reduce beam damage
284 eV 280 eV
RSoXS applications
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11.0.1.2 Beamline at the ALS
Ener
gy (
eV)
X-Rays
Main chamber
C. Wang I. Cordova
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284.6 eV 285.2 eV
CD-GIRSOXS of latent imageChain-scission EUV resist:
✓ E-beam exposition ✓ 200 nm pitch line gratings✓ Post-Exposure baking
t1
t2
Exposition + bake:Chain scission
Modification of the carbon environment Modification of the β and δ
Introduction of a scattering contrast
NEXAFS spectra of the resist
Energy (eV)
Peak related to a specific carbon
bonds
Contrast between exposed/unexposed resist at 284.6 eV
✓ 284.6 eV: Electronic density contrast✓ 285.2 eV: No electronic density contrast
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CD-GISAXS of latent image using Resonant scattering
Reconstruction of the 3D shape of a latent image
123
1
2
3
Extracted profile
1D vertical cut
10
✓ New perspectives to control the 3D shape of a latent image✓ Short measurement time: 10 seconds✓ Beam damage?
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Conclusion
✓ 3D reconstruction of the latent image with a sub-nm resolution
✓ Trapezoidal shape after the exposition
✓ Comparison before and after development
vs
FEM wafer (IMEC)
✓ Test on different resists (different elements edges)
✓ Quantification of the roughness
✓ Study beam damage on the sample
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Acknowledgements
Isvar CordovaTerry McAfeeWei XuGreg SuDavid KilcoyneCheng WangAlexander Hexemer
Thank you for your attention!
Patrick NaulleauWeilun ChaoChristopher Anderson
Daniel StaaksScott DhuevPeter Ercius
Ronal PandolfiDinesh KumarJamie A. Sethian
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Acknowledgements
Thank you for your attention!