tSAXS量測於半導體產業之應用

1. tSAXS量測於半導體產業之應用
吳文立 (Wen-li Wu)
CMS Advisor, ITRI
Fellow Emeritus
National Institute of Standards and Technology
AOI論壇 10/15/2014

2. We have demonstrated that Small Angle X-ray Scattering in transmission
mode (tSAXS) is capable of measuring the average pitch size and the line width
of deep sub-micrometer line gratings with a sub-nanometer precision. We have
further developed a protocol enabling the extraction of additional cross-section
information including line height and sidewall angle from the SAXS data.
Diffraction peak intensities and peak positions are measured while the sample is
rotated around the axis parallel to the grating lines. The scattering intensities
and the peak position at each rotation angles can be compiled in a way that the
resulted diagram represents the cross section of the line in Fourier space.
Examples of applying tSAXS to determine line edge roughness, standing wave
roughness in photoresist patterns, high-k layer thickness on FinFET and other
complex cross sections will be presented.
ABSTRACT
AOI論壇 10/15/2014

3. Acknowledgements:
ChengqingWang (NIST now at KLA-Tencor)
Ronald Jones (NIST)
Tengju Hu (NIST now at DuPont in Shanghai)
Eric K. Lin (NIST)
R. Joseph Kline (NIST)
Kwang-woo Choi (Intel retired)
GeorgeThompson (Intel)
James S. Clarke (Intel)
Qinghuang Lin (IBM)
Steven J.Weigand (APS in Argonne Nat’l Lab)
DenisT. Keane (APS in Argonne Nat’l Lab)
Benjamin Bunday (Sematech)
NIST / Intel CRADA 1893
NIST Office of Microelectronics Program
AOI論壇 10/15/2014

4. tSAXS is a technique to characterize nanostructures quantitatively and
was pioneered in 2000 byWu. Its main advantages over optical
techniques and SEM are:
1. Short wavelength ~ 1 Å or less, hence, high intrinsic resolution
compared to any optical methods
2. High penetration power at this short wavelength, hence, applicable
to buried structures, deep holes and structures with high aspect ratio.
3.Weak reaction with most materials, hence, non-invasive and the
experimental data can be analyzed with a simple Fourier inversion.
The main drawback is its long measurement time due to the lack of
a laboratory based high brilliance X-ray source. Synchrotron X-ray
source is not an option for daily measurements by industries. To
address this drawback efforts have been launched withWei-En Fu’s
team in CMS.
Introduction
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5. X-rays were discovered byWilhelm Conrad Röntgen in 1895, just as the
studies of crystal symmetry were being concluded. Von Laue’s pioneer
work using X-rays on a copper sulfate crystal and record its diffraction
pattern on a photographic plate (Nobel Price in Physics 1914) marks the
beginning of using X-ray diffraction to explore the beauty of symmetry of
crystal lattices, this includes the work by Rosalind Franklin on the double-
helix structure of DNA in 1950’s.
There is a basic difference between the X-ray diffraction and tSAXS; the
focus of former is the lattice structure whereas the form factor of the
constituting object is the focus of tSAXS. For semiconductor industries
the constituting object can be a via, a photoresist line or a FinFET. An
important goal of tSAXS is to determine the structure details of these
objects.
I(q) ~ L(q) F(q) where I(q) is the X-ray scattering intensity at a scattering
vector q . The lattice factor L(q) is the main focus of crystallography or
traditional X-ray diffraction whereas F(q) is the target of tSAXS.
AOI論壇 10/15/2014

6. Transmission SAXS
• Silicon transparent for E > 13 keV
• Non-destructive / No sample prep
Use scatterometry targets
• Beam spot size (40x40) mm
Measure “3-D” and Buried patterns
• Contact holes
• Multilevel interconnects
High Precision for sub-45 nm
• Sub-nm precision in pitch and linewidth
• Pattern Cross Section
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7. • Since 2005 tSAXS (called CD-SAXS then) has been listed in
InternationalTechnology Roadmap for Semiconductors [1] as a
potential solution to many future metrology needs.
• SEMATECH, Bruker, Excillum and NIST started a joint effort to evaluate a
new liquid metal jet X-ray source for industrial application
• KLA-Tencor and Applied Materials have also started their efforts on
tSAXS
• The current consensus is that the new X-ray source is still inadequate for
industrial applications
1. The International Technology Roadmap for Semiconductors is a set of documents
produced by a group of semiconductor industry experts.These experts are representative of the
sponsoring organizations which include the Semiconductor Industry Associations of the US,
Europe, Japan, South Korea and Taiwan.
The documents represent best opinion on the directions of research into the following areas of
technology, including time-lines up to about 15 years into the future.
Current State ofThe Art of tSAXS
AOI論壇 10/15/2014

8. Normal Incidence Scattering:
• Pitch & its modulation which occurs
often in double or quadruple patterning
• Average line width
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9. d
d = 237.1  0.5 nm
-10 -5 0 5 10
0.000
0.005
0.010
0.015
0.020
0.025
0.030
q(A
-1
)
Peak order
Pitch Measurement
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10. 0.000 0.006 0.012 0.018 0.024 0.030
10
2
10
3
10
4
10
5
experimental
rectangle model, resolution function,
Debye-Waller effect
Intensity
q (A
-1
)
W
d
Average Line Width
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11. 
x
z
y
Sidewall Angle : start with a Trapezoid cross section
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12. qx
qz
I
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13. 0 0.005 0.01 0.015 0.02
-0.01
-0.005
0
0.005
0.01
qx
qz
1
2
5


1’
2’
3’
3
4
w
2q
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14.  qx
qz
h
real space Fourier space
qx
qz

2π/h
cross section of a grating line
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15. 0.15
0.10
0.05
0.00
-0.05
-0.10
-0.15
qz(RelativetoSample)(nm
-1
)
0.50.40.30.20.10.0
qx (Relative to Sample) (nm
-1
)
60
40
20
0
6005004003002001000
IBM DOF p4
+0.4 micron
Period = (330.5 ± 0.5) nm
Linewidth = (160 ± 1) nm
Height = (460 ± 10) nm
Sidewall Angle = (5.6 ± 0.5)°
Random Deviation = 5 nm
2 
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16. 1. Wu, W.; Lin, E. K.; Lin, Q. H.; Angelopolous, M., Small angle neutron scattering measurements of nanoscale lithographic features. J. Appl. Phys. 2000, 88 (12), 7298-7303.
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(19), 4059-4061.
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Polym. Sci. Pt. B-Polym. Phys. 2004, 42 (6), 1106-1113.
4. Hu, T. J.; Jones, R. L.; Wu, W. L.; Lin, E. K.; Lin, Q. H.; Keane, D.; Weigand, S.; Quintana, J., Small angle x-ray scattering metrology for sidewall angle and cross section of nanometer scale
line gratings. J. Appl. Phys. 2004, 96 (4), 1983-1987.
5. Jones, R. L.; Hu, T.; Soles, C. L.; Lin, E. K.; Wu, W.; Casa, D. M.; Mahorowala, A., Preliminary evaluation of line-edge roughness metrology based on CD-SAXS. Metrology, Inspection, and
Process Control for Microlithography Xviii, Pts 1 and 2 2004, 5375, 191-198.
6. Jones, R. L.; Lin, E. K.; Lin, Q. H.; Weigand, S. J.; Keane, D. T.; Quintana, J. P.; Wu, W. L., Cross section and critical dimension metrology in dense high aspect ratio patterns with CD-SAXS.
Characterization and Metrology for ULSI Technology 2005 2005, 788, 403-406.
7. Jones, R. L.; Lin, E. K.; Qinghuan, L.; Weigand, S. J.; Keane, D. T.; Quintana, J. P.; Wen-li, W., Cross section and critical dimension metrology in dense high aspect ratio patterns with CD-
SAXS. AIP Conference Proceedings 2005, (788), 403-6.
8. Jones, R. L.; Lin, E. K.; Wu, W. L.; Weigand, S. J.; Keane, D. T.; Quintana, J. M., Cross sectional measurements of dense high aspect ratio patterns using CD-SAXS. Metrology, Inspection,
and Process Control for Microlithography XIX, Pts 1-3 2005, 5752, 404-411.
9. Jones, R. L.; Soles, C. L.; Lin, E. K.; Hu, W.; Reano, R. M.; Pang, S. W.; Weigand, S. J.; Keane, D. T.; Quintana, J. P., Pattern fidelity in nanoimprinted films using CD-SAXS. Emerging
Lithographic Technologies IX, Pts 1 and 2 2005, 5751, 415-422.
10. Jones, R. L.; Hu, T. J.; Soles, C. L.; Lin, E. K.; Reano, R. M.; Casa, D. M., Real-time shape evolution of nanoimprinted polymer structures during thermal annealing. Nano Letters 2006, 6 (8),
1723-1728.
11. Jones, R. L.; Soles, C. L.; Lin, E. K.; Hu, W.; Reano, R. M.; Pang, S. W.; Weigand, S. J.; Keane, D. T.; Quintana, J. P., Pattern fidelity in nanoimprinted films using critical dimension small
angle x-ray scattering. Journal of Microlithography Microfabrication and Microsystems 2006, 5 (1).
12. Jones, R. L.; Wu, W. L.; Wang, C. Q.; Lin, E. K.; Kwang-Woo, C.; Rice, B. J.; Thompson, G. M.; Weigand, S. J.; Keane, D. T., Characterization of line edge roughness using CD-SAXS - art.
no. 61520N. Metrology, Inspection, and Process Control for Microlithography XX, Pts 1 and 2 2006, 6152, N1520-N1520.
13. Knight, S.; Dixson, R.; Jones, R. L.; Lin, E. K.; Orji, N. G.; Silver, R.; Villarrubia, J. S.; Vladar, A. E.; Wu, W. L., Advanced metrology needs for nanoelectronics lithography. Comptes
Rendus Physique 2006, 7 (8), 931-941.
14. Chengqing, W.; Jones, R. L.; Lin, E. K.; Wen-li, W.; Villarrubia, J. S.; Kwang-Woo, C.; Clarke, J. S.; Rice, B. J.; Leeson, M. J.; Roberts, J.; Bristol, R.; Bunday, B., Line edge roughness
characterization of sub-50 nm structures using CD-SAXS: round-robin benchmark results. Proceedings of the SPIE - The International Society for Optical Engineering 2007, 65181O (9 pp.).
15. Ho, D. L.; Wang, C. Q.; Lin, E. K.; Jones, R. L.; Wu, W. L., A laboratory scale critical-dimension small-angle x-ray scattering instrument. Frontiers of Characterization and Metrology for
Nanoelectronics: 2007 2007, 931, 382-386.
16. Ro, H. W.; Jones, R. L.; Peng, H.; Hines, D. R.; Lee, H. J.; Lin, E. K.; Karim, A.; Yoon, D. Y.; Gidley, D. W.; Soles, C. L., The direct patterning of nanoporous interlayer dielectric insulator
films by nanoimprint lithography. Adv. Mater. 2007, 19 (19), 2919-+.
17. Wang, C. Q.; Jones, R. L.; Lin, E. K.; Wu, W. L.; Ho, D. L.; Villarrubia, J. S.; Choi, K. W.; Clarke, J. S.; Roberts, J.; Bristol, R.; Bunday, B., Line edge roughness and cross sectional
characterization of sub-50 nm structures using critical dimension small angle x-ray scattering. Frontiers of Characterization and Metrology for Nanoelectronics: 2007 2007, 931, 402-406.
18. Wang, C. Q.; Jones, R. L.; Lin, E. K.; Wu, W. L.; Villarrubia, J. S.; Choi, K. W.; Clarke, J. S.; Rice, B. J.; Leeson, M.; Roberts, J.; Bristol, R.; Bunday, B., Line edge roughness characterization
of sub-50nm structures using CD-SAXS: Round-robin benchmark results - art. no. 65181O. Metrology, Inspection, and Process Control for Microlithography XXI, Pts 1-3 2007, 6518, O5181-
O5181.
19. Chengqing, W.; Kwang-Woo, C.; Jones, R. L.; Soles, C.; Lin, E. K.; Wen-li, W.; Clarke, J. S.; Villarrubia, J. S.; Bunday, B., Linewidth roughness and cross-sectional measurements of sub-50
nm structures with CD-SAXS and CD-SEM. Proceedings of the SPIE - The International Society for Optical Engineering 2008, 69221Z-1-8.
20. Chengqing, W.; Kwang-Woo, C.; Wei-En, F.; Ho, D. L.; Jones, R. L.; Soles, C.; Lin, E. K.; Wen-Li, W.; Clarke, J. S.; Bunday, B., CD-SAXS measurements using laboratory-based and
synchrotron-based instruments. Proceedings of the SPIE - The International Society for Optical Engineering 2008, 69222E-1-7.
tSAXS Dimensional Metrology References
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17. 21. Chengqing, W.; Kwang-Woo, C.; Wei-En, F.; Jones, R. L.; Ho, D. L.; Soles, C.; Lin, E. K.; Wen-li, W.; Clarke, J. S.; Villarrubia, J. S.; Bunday, B., Linewidth roughness and cross-sectional
measurements of sub-50 nm structures using CD- SAXS and CD-SEM. 2008 IEEE/SEMI Advanced Semiconductor Manufacturing Conference 2008, 142-7.
22. Hyun Wook, R.; Jones, R. L.; Huagen, P.; Hae-Jeong, L.; Lin, E. K.; Karim, A.; Yoon, D. Y.; Gidley, D. W.; Soles, C. L., Porosity characteristics of ultra-low dielectric insulator films directly
patterned by nanoimprint lithography. Proceedings of the SPIE - The International Society for Optical Engineering 2008, 69211M-1-11.
23. Ro, H. W.; Jones, R. L.; Peng, H.; Lee, H. J.; Lin, E. K.; Karim, A.; Yoon, D. Y.; Gidley, D. W.; Soles, C. L., Porosity characteristics of ultra-low dielectric insulator films directly patterned by
nanoimprint lithography - art. no. 69211M. Emerging Lithographic Technologies Xii, Pts 1 and 2 2008, 6921, M9211-M9211.
24. Ro, H. W.; Peng, H.; Niihara, K. I.; Lee, H. J.; Lin, E. K.; Karim, A.; Gidley, D. W.; Jinnai, H.; Yoon, D. Y.; Soles, C. L., Self-sealing of nanoporous low dielectric constant patterns fabricated
by nanoimprint lithography. Adv. Mater. 2008, 20 (10), 1934-+.
25. Wang, C.; Choi, K. W.; Jones, R. L.; Soles, C.; Lin, E. K.; Wu, W. L.; Clarke, J. S.; Villarrubia, J. S.; Bunday, B., Linewidth roughness and cross-sectional measurements of sub-50 nm
structures with CD-SAXS and CD-SEM - art. no. 69221Z. Metrology, Inspection, and Process Control for Microlithography Xxii, Pts 1 and 2 2008, 6922 (1-2), Z9221-Z9221.
26. Wang, C. Q.; Choi, K. W.; Fu, W. E.; Ho, D. L.; Jones, R. L.; Soles, C.; Lin, E. K.; Wu, W. L.; Clarke, J. S.; Bunday, B., CD-SAXS measurements using laboratory-based and synchrotron-
based instruments - art. no. 69222E. Metrology, Inspection, and Process Control for Microlithography Xxii, Pts 1 and 2 2008, 6922 (1-2), E9222-E9222.
27. Wang, C. Q.; Choi, K. W.; Fu, W. E.; Jones, R. L.; Ho, D. L.; Soles, C.; Lin, E. K.; Wu, W. L.; Clarke, J. S.; Villarrubia, J. S.; Bunday, B., Linewidth roughness and cross-sectional
measurements of sub-50 nm structures using CD-SAXS and CD-SEM. 2008 IEEE/SEMI Advanced Semiconductor Manufacturing Conference 2008, 142-147.
28. Chengqing, W.; Kwang-Woo, C.; Yi-Ching, C.; Price, J.; Ho, D. L.; Jones, R. L.; Soles, C.; Lin, E. K.; Wen-Li, W.; Bunday, B. D., Nonplanar high-k dielectric thickness measurements using
CD- SAXS. Proceedings of the SPIE - The International Society for Optical Engineering 2009, 72722M (8 pp.).
29. Wang, C. Q.; Fu, W. E.; Li, B.; Huang, H.; Soles, C.; Lin, E. K.; Wu, W. L.; Ho, P. S.; Cresswell, M. W., Small angle X-ray scattering measurements of spatial dependent linewidth in dense
nanoline gratings. Thin Solid Films 2009, 517 (20), 5844-5847.
30. Yokhin, B.; Krokhmal, A.; Dikopoltsev, A.; Berman, D.; Mazor, I.; Lee, B. H.; Ihm, D. C.; Kim, K. H., Compact X-ray Tool For Critical-Dimension Metrology. Frontiers of Characterization and
Metrology for Nanoelectronics: 2009 2009, 1173, 364-368.
CD-SAXS Dimensional Metrology References
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18. The Advanced Photon Source
• APS is the first synchotron to feature a constant x-ray
flux.
• Most synchrotrons have decaying fluxes that are
“refilled” every 10-12 hours
AOI論壇 10/15/2014

19. Lab Scale tSAXS Prototype
• Beam flux ~4 to 5 orders of magnitude below APS
• Installed November 2005
Intel test grating with 400nm pitch
Cu seeded lines
Nanoimprint array of 60 nm holes
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20. FinFET with high-k dielectric
qx
qy
O
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21. 𝑠𝑙𝑜𝑝𝑒 = 2𝜋/𝐿
L is the pitch which is
almost double that of the
intended pitch of ~200nm
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22. Definitions:
CD: silicon width
w: line width (CD) + High-k thickness
d: High-k thickness
L: effective pitch
r1: electron density of High-k dielectric
(2.012 e/Å 3)
r2: electron density of silicon
(0.699 e/Å 3)
Samples Descriptions:
Larger array/cell of ~ 300 x 700um
200nm Pitch
1) Si (CD = 50nm), no HfSiOx
2) Si (CD = 30nm), no HfSiOx
3) Si (CD = 30nm), 2 nm HfSiOx
4) Si (CD = 30nm), 4 nm HfSiOx
5) Si (CD = 30nm), 7 nm HfSiOx
6) Si (CD = 30nm), 10 nm HfSiOx
Lw
Pitch Shift
CD (w-2d)
HfSiOx
Si

23. Im g: 'E6183 081204003_ Piec es _ 06_ 300x 700um _ s c at t erom et ry _ rot _ s . dm 3' M AG: 15k X
0 . 2 µ m0 . 2 µ m
Bright-FieldTEM images of the sample in cross-
section, showing higher magnifications images
of the FinFETs.Two different pitch values
were measured in the analyzed structure,
approximately 190 nm and 204 nm.
X-TEM

24. 0 0.2 0.4 0.6 0.8 1 1.2
0
5
10
15
20
25
30
35
40
Qx /nm
-1
Intensity/a.u.
0 nm
1 nm
2 nm
5 nm
signature of pitch modulation
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25. ∆𝑞 𝑥 = 2𝜋/𝑤
signature of high-k layer thickness
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26. AOI論壇 10/15/2014

27. Group Meeting
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q-range for signature of
high-k dielectric (9.2nm)

28. Group Meeting
0
2
4
6
8
10
12
0 4 8 12
X-TEM(UpperLimit)
CD-SAXS (Synchrotron)
Input Data
Mandel Fit
0
2
4
6
8
10
12
0 4 8 12
X-TEM(LowerLimit)
CD-SAXS (Synchrotron)
Input Data
Mandel Fit
Slope Average Offset
Num Pair Estimate 3 Sigma Intercept Estimate 3 Sigma
4 1.005 0.219 0.94 -0.97 0.859
Slope Average Offset
Num Pair Estimate 3 Sigma Intercept Estimate 3 Sigma
4 0.959 0.162 0.58 -0.35 0.859
High-k thickness: X-TEM vs. Synchrotron CD-SAXS

29. Group Meeting
Average Line width w/high-k: CD-SAXS (Synchrotron vs. Laboratory)
20
30
40
50
20 30 40 50
CD-SAX(Laboratory)
CD-SAXS (Synchrotron)
Input Data
Mandel Fit
Slope Average Offset
Num Pair Estimate 3 Sigma Intercept Estimate 3 Sigma
7 0.985 0.021 0.36 0.10 0.621

30. Group Meeting
High-k thickness comparison, CD-SAXS Synchrotron vs. Laboratory
0
2
4
6
8
10
12
0 2 4 6 8 10 12
CD-SAX(Laboratory)
CD-SAXS (Synchrotron)
Input Data
Mandel Fit
Slope Average Offset
Num Pair Estimate 3 Sigma Intercept Estimate 3 Sigma
7 0.994 0.077 -0.29 0.33 0.621

31. LER/LWR measurements with tSAXS
Potential for LER related quantities:
• Distribution in Periodicity
• Periodic errors (stitching and standing wave)
• Distribution in cross sectional shape
• Frequency spectrum of sidewall roughness??
CD-SAXS and CD-SEM, CD-AFM:
• Average vs. Single line
• LER, LWR, and possible other classes of
variation.
• 3-D Average vs. top-down image
CD-SAXS and OCD:
• Measure same targets
• Help develop OCD in current nodes
• Potential workhorse for sub-45 nm
LER
LWR
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32. SAXS result of A LER Sample
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33. Standing Waves on the wall?
Complex cross section – example I
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34. #125 PR
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35. -0.2 -0.1 0.0 0.1 0.2
10
2
10
3
10
4
qx
= 0.194 nm
-1
Height ~ 360 nm
wavelength ~ 72 nm
qz
/ nm
-1
Intensity Experimental
Amplitude 0 nm
Amplitude 3 nm
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36. Complex cross section – example II
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37. AOI論壇 10/15/2014
Wafer 1, cell 1

38. 6.792

SixTrapezoids (Heights floated)
SWA=84.2o
SWA=88.9o
SWA=88.4o
72.4
83.5
165.963.5131.1
SWA=87.0o
78.5
SWA=85.3o
8.2
SWA=37.4o
Total Height: 439.1
47.6
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Wafer 1, cell 1

39. 8.1852

SixTrapezoids (Heights scaled to design value)
SWA=83.9o
SWA=87.5o
SWA=88.8o
76.5
34.9
89.569.6
238.7
SWA=87.0o
39.8
SWA=85.0o
8.3
SWA=32.4o
Total Height: 438.6
203.8
Wafer 1, cell 1
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40. Conclusions:
tSAXS has been used successfully to demonstrate its
capability to measure pitch, line width, line height,
sidewall angle, thickness of non-planar high-k dielectric
layer on FinFET, line edge roughness, standing wave
roughness in photoresist lines and some complicated
cross sectional profiles.
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