EUV Symposium TWG, Toyama Japan Molecular Organometallic Resists for EUV (MORE) October 6, 2013 I. Introduction II. Organo-Tin Complexes III. Ligand Studies: Oxalate Anions IV. Summary Brian Cardineau, 1 James Passarelli, 1 Miriam Sortland, 1 Ryan Del Re, 1 Westly Tear, 1 Hashim Al-Mashat, 2 Miles Marnell, 2 Kara Heard, 2 Amber Aslam, 2 Jason Pavlich, 2 Rachel Kaminski, 2 Peter Nastasi, 2 Chandra Sarma, 3 Dan Freedman, 2 Robert Brainard 1 1. CNSE 2. SUNY New Paltz 3. Sematech Presenter Wang Yueh, Intel 1 Financial Support by Intel and Sematech
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EUV Symposium TWG, Toyama Japan
Molecular Organometallic Resists for EUV (MORE) October 6, 2013
I. Introduction
II. Organo-Tin Complexes
III. Ligand Studies: Oxalate Anions
IV. Summary
Brian Cardineau,1 James Passarelli,1 Miriam Sortland,1 Ryan Del Re,1 Westly Tear,1
Hashim Al-Mashat,2 Miles Marnell,2 Kara Heard,2 Amber Aslam,2 Jason Pavlich,2
Rachel Kaminski,2 Peter Nastasi,2 Chandra Sarma,3 Dan Freedman,2 Robert Brainard1
1. CNSE
2. SUNY New Paltz
3. Sematech
Presenter Wang Yueh, Intel
1
Financial Support by
Intel and Sematech
EUV Symposium TWG, Toyama Japan
Recent Advances in Inorganic Photoresists
7-nm h/p lines
294 mJ/cm2
A B
Hafnium-Oxide Nanoparticles
Inpria
12-nm h/p lines
25 mJ/cm2
8-nm h/p lines
47 mJ/cm2
36-nm h/p lines
12 mJ/cm2
Cornell
Recently, some researchers have developed new EUV resists based on
inorganic compounds and nanoparticles with excellent performance.
HSQ
Ekinci et al., Proc. SPIE, 2013, 8679.
Trikeriotis et al., Proc. SPIE, 2012, 8322.
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EUV Symposium TWG, Toyama Japan
Molecular Organometallic Resists for EUV (MORE)
We have proposed a new EUV resists consisting of
molecular inorganic or organometallic compounds that
utilize metal centers with high EUV optical density.
Potential Benefits:
1. High EUV OD: Maximize the use of precious EUV photons.
2. High Mass Density: The mean-free path of secondary-electrons is shorter in
high mass-density materials. For resists this would result in a decrease in
electron blur.
3. No Acid Diffusion: No acid catalysis.
4. Excellent Etch Rates: Metal oxide films can have significantly better etch
performance than even the best organic films (HfO2 ~ 25x better).*
5. High Uncatalyzed Reactivity: Since metals have a large range of redox
potentials, resist chemistry can be engineered for high sensitivity without
acid catalysis.
3
* Trikeriotis et al., Proc. SPIE, 2012, 8322.
EUV Symposium TWG, Toyama Japan
Optical Density of the Elements The MORE program is exploring the utility of compounds made from
the darkest elements in the periodic table.
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EUV Symposium TWG, Toyama Japan
Processing of MORE Compounds
5
Pure MORE compounds were spin-cast from organic solvents
• 1.5 to 3% Solids
• Solvents: Mixtures of MEK, THF, Hexane, CH2Cl2, Water, IPA.
• Most films had no other additives
• Soft bakes were generally not used.
• Film thicknesses were 30-50 nm.
EUV Exposures
• Berkeley exposures used the DCT and produced contrast curves.
• PSI exposures produced dense-line patterns. 18 nm was the smallest
feature on the masks.
Development
• Solvents were selected that just cleared the resists in 30-60 seconds.
• Developer Solvents: Mixtures of MEK, THF, Hexane, CH2Cl2, Water,
IPA.
Negative Tone
• Although some positive-tone behavior has been observed, everything
presented today is of negative-tone resists.
EUV Symposium TWG, Toyama Japan
II. Organo-Tin Complexes
Tin is one of the darkest elements in the periodic table.
Tin is used as “fuel” in many EUV sources.
Kuhlman et al., 2005 US Patent 20050288176 .
A. Mononuclear Tin Complexes
B. Sn-12 Oxo Complexes
Cl-
Cl-
Preliminary Results
showed 20 mJ/cm2
Negative-Tone Sensitivity
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EUV Symposium TWG, Toyama Japan
A. Evaluation of Eleven Mononuclear Tin Complexes
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EUV Symposium TWG, Toyama Japan
B. Possible Mechanisms for Photoreactivity of
Sn-12 Oxo Clusters 1. Anionic Ligand Dissociation
2. Homolysis of Sn-C Bond
3. Sn-O Metathesis
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EUV Symposium TWG, Toyama Japan
Tin-12 Oxocluster Investigation
1) Anionic Ligand Dissociation
What effect does changing the anionic ligand have on resist performance?
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EUV Symposium TWG, Toyama Japan
Effect of Counter-Ion Structure on ESize
Bond Dissociation Energy (Kcal/mol)
Luo, Handbook of Bond Dissociation Energies in Organic Compounds, (2003).
* - Value calculated through H-R bond energy
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EUV Symposium TWG, Toyama Japan
BMET Results: Contrast Curves
Expected Decarboxylation Reactivity
The resist sensitivity seems to
be affected more by ligand bulk
and less by decarboxylation.
Therefore, anion decomposition
is probably NOT the
photochemical mechanism.
Em
ax
BMET
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EUV Symposium TWG, Toyama Japan
4.9 560 4.5 520 2.9 380 5.6 380 8.9 350
LER (nm) Dose (mJ/cm2)
9.4 560 6.2 520 7.7 380 8.1 380 13 350
3.9 500 3.6 480 3.8 350 5.5 350 14 320
3.9 560 3.6 520 3.8 380 5.5 760 14 700
7.3 560 9.0 520 7.6 380 9.0 380
3.0 560 2.5 520
Tin metal-oxide
films are capable of
resolving 18-35 nm,
but sensitivity is a
problem.
18 22 25 35 50 h/p CD (nm)
(PSI March 2013)
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EUV Symposium TWG, Toyama Japan
III. Ligand Studies: Oxalate Anions
1. Known, useful photochemistry:
2. Ease of synthesis for a wide variety of metals
and ancillary ligands. - We have synthesized over 30 new compounds, selected to give
systematic information on the EUV photochemistry of metal oxalate
compounds.
• Crosslinking through open
coordination sites.
• Metal is both reduced and
has lower coordination
number, changing solubility.
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EUV Symposium TWG, Toyama Japan
Central Metal
Through this work we have tested Cr, Fe, Co, Cu and Ni oxalate complexes.
In general:
• Cu and Ni form 4-coordinate complexes with poor solubility.
• Fe complexes are often very crystalline and difficult to get coatings of.
• The general reactivity is in the order of Cr ≤ Fe < Co.
Cr Co
Emax = 8 mJ/cm2 Emax = 35 mJ/cm2
BMET
14
NP1
EUV Symposium TWG, Toyama Japan
Central Metal
Through this work we have tested Cr, Fe, Co, Cu and Ni oxalate complexes.
In general:
• Cu and Ni form 4-coordinate complexes with poor solubility.
• The general reactivity is in the order of Cr < Fe ≤ Co.
The metals are all in the +3 oxidation state.
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NP1
EUV Symposium TWG, Toyama Japan
Oxalate Loading
>1400 ~40 8 3 Emax(mJ/cm2):
Through this work we have also tested the effect of oxalate loading on resist
sensitivity. Increasing oxalate from 0 to 3 improves sensitivity by several
orders of magnitude (1400 to 3 mJ/cm2).
*
BMET
16
NP1
EUV Symposium TWG, Toyama Japan
NP1 Imaging Studies
PSI
3.0 3.3 4.0 7.1LER (nm):
Resolution
h/p (nm): 35 25 22 18
MEK Develop / 15s
30 nm Thickness
Dose of 30 mJ/cm2
PAB = 90°/60s
PEB = None
(PSI March 2013) 17
EUV Symposium TWG, Toyama Japan
18 22 25 35 50 h/p CD (nm):
A bake study was performed and a PAB of
90° for 60s with no PEB appears to perform
the best.
NP1 – Bake Study MEK Develop / 15s
43 nm Thickness
30 27 20 20 19
30 27 20 20 19
27 25 18 18 17
Dose (mJ/cm2)
4.3
4.9
4.1 3.7
5.7
3.5
PAB (None)
PEB (None)
PAB (90°/60s)
PEB (90°/60s)
PAB (90°/60s)
PEB (None)
LER (nm)
Imaging Conducted at PSI 18
EUV Symposium TWG, Toyama Japan
IV. Summary
• Over a hundred compounds were tested for spin-coating and EUV
sensitivity during Year 1 under Intel.
• About half of the complexes have good coating and good air
stability.
• We have discovered 6-10 new MORE complexes with 18 nm
resolution.
• Most coatings showed some EUV sensitivity, although some were
quite slow (70-700 mJ/cm2).
• Oxalate has proven to be an excellent ligand and produces highly
sensitive non-chemically amplified resists.
• Our best resist (NP1) is capable of ~22 nm dense lines at ~20
mJ/cm2.
• In year 2 of MORE, under Sematech, we plan to continue to develop
the successful resists we have, while developing new platforms:
o Improve Current Platforms
o Explore New Platforms
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EUV Symposium TWG, Toyama Japan
Acknowledgements
Michaela Vockenhuber
Yasin Ekinci
And you for your time…
Staff at PSI: Financial Support:
Intel Corporation
Steve Putna
Wang Yueh
Sematech
Mark Neisser
Stefan Wurm
Patrick Naulleau
Brian Hoef
Lori Mae Baclea
Gideon Jones
Paul Denham
Staff at LBNL:
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EUV Symposium TWG, Toyama Japan
Appendix
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EUV Symposium TWG, Toyama Japan
Expected Metal-Oxide Etch Rates
The etch rates for most metal oxides are unknown. However, due to the high
melting points / boiling points of the metal fluorides, we expect extremely