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Laura Evangelio1,2, Matteo Lorenzoni1, Jordi Fraxedas2, Francesc Pérez-Murano1,
1Institut de Microelectrònica de Barcelona (IMB-CNM, CSIC)2Institut Català de Nanociència i Nanotecnologia (ICN2, CSIC)
Campus UAB, 08193-Bellaterra, Barcelona
Determination of the interfacial
energies in chemical guiding patterns
for directed self-assembly
of block co-polymers
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A B
A B A
Diblock – AB –
Triblock – ABA –
� The morphology of the BCP depends on the ratio between the molecular weights of both blocks:
Block co-polymer self-assembly
Disordered Ordered
Thermal
Annealing
A B
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� The block copolymer pitch (L0) depends on its molecular weight.
Polymer chain length = Polymer period
PMMA PS
BC
P m
ole
cula
r w
eig
ht
BLOCK CO-POLYMER SELF ASSEMBLY
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Intrinsic property of
BCP to self-assemble
Traditional lithographic
techniquesGuiding of the BCP
+ =n·L0L0
PS-b-PMMA
PS-b-PEO
PS-b-PDMS
EBL
DUV
EUV
Chemical epitaxy
Graphoepitaxy
DIRECTED SELF – ASSEMBLY OF BLOCK COPOLYMERS
� Introduction to the Directed Self-Assembly (DSA) of Block Copolymers (BCP)
Lithography resist
Si
Almost neutral
area Preferential area for
one of the blocks
Si
SiSi
Graphoepitaxy
Chemical epitaxy
DIRECTED SELF-ASSEMBLY METHODS
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CHEMICAL EPITAXY METHODS
C.-C.Liu, E. Han, M.S.Onses,C.J.Thode, S. Ji, P. Gopalan, P.F. Nealey “Fabrication of
Lithographically Defined Chemically Patterned Polymer Brushes and Mats“
Macromolecules, 44, 1876, 2011
LINE Process (Wisconsin) IBM Process
J. Y., Sanders, D. P., Truong, H. D., Harrer, S., Friz, A., Holmes, S., ...
& Hinsberg, W. D.“Simple and versatile methods to integrate
directed self-assembly with optical lithography using a polarity-
switched photoresist“ ACS Nano, 4(8), 4815-4823, 2010
SMART Process
Jihoon Kim, Jingxiu Wan, Shinji Miyazaki, Jian Yin, Yi Cao, Young Jun Her, Hengpeng Wu, Jianhui Shan,
Kazunori Kurosawa, Guanyang Lin.
"The SMART(TM) Process for Directed Block Co-Polymer Self-assembly“
Journal of Photopolymer Science and Technology 26, 573-579, 2013
→ BCP: PS-b-PMMA
(hp = L0/2 = 18.5 nm, 14 nm,11 nm) and thermal annealing
→ Brush layer: PS-OH, PS-r-PMMA using several annealing conditions
→ Chemical functionalization: Exposure to O2 plasma (two conditions: soft, strong)
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1. Brush (grafting) to
the silicon substrate
3. O2 plasma
functionalization
4. DSA of PS-b-PMMA
2. Electron beam
lithography
PS-b-PMMA 11 nm hp
(From ARKEMA)
PROCESS AND MATERIALS
L. Oria,, A.R. de Luzuriaga, J, Alduncin, F. Perez-Murano,
“Polystyrene as a brush layer for directed self-assembly of block co-polymers”
/Microelectronic Engineering,/ 113,234, 2013,
BA
SIA Lithography Roadmap 2013
8
DENSITY MULTIPLICATION AND CHEMICAL EPITAXY
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∆γ=γSA- γSB is the main driving force in directed self-assembly by chemical epitaxy
The proper achievement of high density multiplication factors requires considering
multiple parameters simultaneously
Dimensional Parameters
Ls Width of guiding stripe
Lb Width of background stripe
L0 Bulk lamella period
d Film thickness
Material Parameters
χNFlory Huggins parameter ·
degree of polymerization
Reo Mean square distance of BCP chains
κNInverse isothermal compressibility ·
degree of polymerization
D Self-difusion coefficient
γSA, γSB
Surface free energies of the segment
species with the confining boundaries
Density multiplication factor
η=(Lb+Ls)/Lo
ROLE OF INTERFACE ENERGIES IN THE CHEMICAL EPITAXY PROCESS
d d
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∆γ=γSA- γSB = γAB · cos (φΑΒ) Kim et al., Macromolecules, Vol. 42, 7919, 2009
���: Interfacial tension => Taken from the literature
∆γ is determined from the Young equation by de-wetting experiments
Polymer APolymer BφΑΒ < 90 º : More affinity to block B
φΑΒ = 90 º : Neutral surface
φΑΒ > 90 º : More affinity to block A
1. Brush (grafting) to the
silicon substrate 3. PS-PMMA dewetting
2. PS/PMMA blend
spin-coating
EXPERIMENTAL DETERMINATION OF INTERFACE ENERGIES
Experimental process
cos (φΑΒ) is determined experimentally
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EXPERIMENTAL DETERMINATION OF INTERFACE ENERGIES
400 nm
Tilted SEM image
Tilted SEM image
Homopolymer blends dewetting on
polymer brush surfaces
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SEM characterization
AFM characterization
Topography Young Modulus
Adhesion Deformation
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Acetic Acid
Φ
Acetic Acid
Φ
PSPMMA PS
PMMA
M. Lorenzoni, L. Evangelio, F. Perez-Murano. JM3 in press.
Un-modified PS-Oh brush Modified PS-OH brush
EXPERIMENTAL DETERMINATION OF INTERFACE ENERGIES
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∆γ = γS-PMMA - γS-PS [mN/m]
Processing conditions Background
stripe
Guiding stripe
(soft plasma)
Guiding stripe
(hard-plasma)Brush material BCP Annealing
PS-OH230ºC for 10 min
in N2
0.35 -0.38 -0.51
PS-OH200ºC for 20 min
in Hot-Plate0.40 -0.80 -0.91
PS0.69-r-PMMA0.31
230ºC for 10 min
in N2
0.13 -0.50 -0.56
The sets of interface energies are the ones that provide suitable conditions for high
multiplication factors
∆γ=γSA- γSB = γAB · cos (φΑΒ)
EXPERIMENTAL DETERMINATION OF INTERFACE ENERGIES
Kim et al., Macromolecules, Vol. 42, 7919, 2009
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DENSITY MULTIPLICATION AND INTERFACE ENERGIES
18.5 nm hp L28 L22
200 nm 200 nm
0.35 -0.38 0.40 -0.80 0.13 -0.50
Background Guiding stripe Background Guiding stripe Background Guiding stripe
(Narrow stripes) η=2
200 nm
(Wide stripes) η=6 (Wide stripes) η=514 nm hp 11 nm hp
Optimal conditions for PS-b-PMMA of several pitch dimensions
∆γ[mN/m]
∆γ[mN/m]
1.5 Lo 0.5 Lo 3.5 Lo 2.5 Lo 2.5 Lo 2.5 Lo
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HIGH DENSITY MULTIPLICATION FACTORS WITH PS-b-PMMA 11 nm hp
300 nm300 nm300 nm
η=3 η=4 η=5
11 nm11 nm11 nm
0.13 -0.50 PS-PMMA 11 nm hp∆γ[mN/m]
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INFLUENCE OF OXYGEN PLASMA FUNCTIONALIZATION STRENGTH
0.40 -0.80 0.40 -0.91
Soft plasma Hard plasma
Background Guiding stripe Background Guiding stripe
∆γ ∆γPS-PMMA 14 nm hp
MNE2015
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17E-MRS Spring Meeting 2015
Lille, May 14th
INFLUENCE OF OXYGEN PLASMA FUNCTIONALIZATION STRENGTH
Soft plasma Hard plasma
PS-PMMA 11 nm hp
100 nm 100 nm
0.13 -0.50 0.13 -0.56
Background Guiding stripe Background Guiding stripe
∆γ ∆γ
1. AFM based nanolithography
2. Electron beam nanolithography direct writing
NOVEL APPROACHES TO CHEMICAL EPITAXY GUIDING PATTERNSNEW METHODS FOR CHEMICAL GUIDING PATTERNS
Fernández-Regúlez, M.; Evangelio, L.; Lorenzoni, M.; Fraxedas, J. and Pérez-Murano, F.,
ACS Appl. Mater. Interfaces 6, 21596 (2014)
xL0
Evangelio, L.; Fernández-Regúlez, M.; Borrise, X.; Lorenzoni, M.; Fraxedas, J. and Pérez-Murano, F.,
J. Micro/Nanolith. MEMS MOEMS 14 (3), 033511 (2015)
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SUMMARY
• Density multiplication by wide guiding stripes can be achieved by
properly tuning of the interface energies
• Density multiplication factor of x6 has been achieved with PS-b-PMMA of 14 nm hp
• Simulations allow to predict the final DSA pattern, and suggest
that the value of interface energy is lowered by the presence of
residual solvent during the annealing
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• Strength of interface energies can be quantified from dewettingexperiments
THANK YOU FOR YOUR ATTENTION
Acknowledgments
CNM Cleanroom staff
Initial work of Marta Fernández-Regúlez
