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Fabrication of nanostructures by means of Block Copolymer based lithography
Monica Ceresoli Supervisor: Prof. Paolo Milani Co-Supervisor: Dr. Michele Perego
2003 90 nm 2005 65 nm Manifacturing 2007 45 nm
Introduction
2009 32nm 2011 22 nm 2013 14 nm Development 2015 10 nm Research
Fabrication issue: sub 20 nm structures
• • •
Requirements:
High density Long range order Simple and short process Implementation of self-assembling materials in Microelectronics lithography.
ITRS 2011 Edition: “Emerging Research Materials”
Introduction
BLOCK COPOLYMERS (BCP): class of macromolecules produced by covalently bonding two or more chemically distinct polymer blocks.
Thermodynamic Incompatibility + Covalent Bond Lamellae Thermal treatment Phase separation in ordered nano-domains
I.Botiz et al., Materials Today 13, 42-51 (2010), F. S. Bates et al., Physics Today 52, 32-38 (1999)
Introduction
Lithographic application of Lamellar thin films.
• • •
Problems:
Long time process.
Weak dependence on Temperature and time of annealing.
Small dimension of ordered domains (correlation length ξ) • • •
Requirements:
High density Long range order Simple and short process
Furnace 100 minutes
Annealing temperature ( ° C) Annealing time (min) R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162, R. Ruiz et al., Adv. Mater. 19, 587–591 (2007)
Introduction
Lithographic application of Lamellar thin films.
• • •
Problems:
Long time process.
Weak dependence on Temperature and time of annealing.
Small dimension of ordered domains (correlation length ξ) • • •
Requirements:
High density Long range order Simple and short process
New study: Thermodynamics on short time-scale
R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162, R. Ruiz et al., Adv. Mater. 19, 587–591 (2007)
Materials and Techniques
Preparation of lamellar thin films.
• Neutralization of the substrate.
Random Copolymer SiO 2 Si
Materials and Techniques
Preparation of lamellar thin films.
• • Neutralization of the substrate.
Block Copolymer deposition.
Block Copolymer Random Copolymer SiO 2 Si Poly (Styrene-block-Methyl Methacrylate)
50% PS 50% PMMA
Materials and Techniques
Preparation of lamellar thin films.
• • • Neutralization of the substrate.
Block Copolymer deposition.
Thermal treatment.
Block Copolymer Random Copolymer SiO 2 Si
Materials and Techniques
Standard thermal process in furnace : Hours!
• • Slow heating and cooling ramp.
Impossibility to fine-tuning the rate of thermal energy transferred to the sample.
Novel approach with Rapid Thermal Processing: Seconds!
• • • Fast heating and cooling ramp.
Real time –control of sample temperature.
Temperatures up above 300 ° C.
Steady state Samples are heated by halogen lamps irradiation.
100 80 60 40 20 0 260 240 220 200 180 160 140 120 80 100 120 Time (s) 140 160 F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601
Experimental Results
Increasing the annealing temperature more and more ordered films get formed.
M. Ceresoli et al., 2013, submitted.
Temperature
Experimental Results
Significant variations of the correlation length (ξ) have been observed.
60s treatment 10s treatment Temperature ( ° C) M. Ceresoli et al., 2013, submitted.
Experimental Results
Two times higher ξ in respect to literature results.
100 minutes conventional furnace 60s treatment 10s treatment
1minute in RTP
time of process reduced by two orders of magnitude ?
Temperature ( ° C) R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162
1s
Experimental Results
5s 10s 60s 5m 15m Time of annealing
290 ° C 270 ° C 250 ° C time (s) R. Ruiz et al., Adv.Mater. 2007,19, 587-591, S. Ji, P.F. Nealey et al., Macrom. (2011) 44.4291.
Experimental Results
Selective remotion of PMMA phase
A double phase appears!
100 nm Residual solvent at the interface with the substrate 100 nm
F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601
1s
Experimental Results
5s 10s 60s 5m 15m Time of annealing Solvent content
cylinders drive order
290 ° C Time (s) On courtesy of Prof. M. Laus, Università del Piemonte Orientale 1 10 100 1000 Time (s)
Perspectives and Open Points
Morphology investigation with Grazing Incident Small Angle X-ray Scattering.
Analysis in progress…
Perspectives and Open Points
The presence of a double phase is affected by solvent choise…
?
Toluene
PS selective PMMA selective
20 nm Acetone Chloroform THF 20 nm 1min, 250 ° C, RTP
Perspectives and Open Points
In very fast thermal treatment, heating and cooling ramps become relevant…
260 240 220 200 180 160 140 120 100 80 60 40 20 0 Steady state 70 65 60 55 50 45 40 80 160 100 120 Time (s) 140 0 • • No significant variation for steady state as long as 30 s.
What about 5 s or 1 s of steady state?
10 20 30 Heating rate ( ° C/s) 40 50
Pubblications
Rapid Thermal Processing of self-assembling block copolymer thin films
F. Ferrarese Lupi, T.J. Giammaria, M. Ceresoli, G. Seguini, K. Sparnacci, D. Antonioli, V. Gianotti, M. Laus and M. Perego. Nanotechnology, 24 (2013) 315601.
Higly ordered lamellar patterns in symmetric block copolymer thin films
M.Ceresoli, F.Ferrarese Lupi, G.Seguini, K. Sparnacci, V. Gianotti, D. Antonioli, M. Laus, L. Boarino and M. Perego.
submitted.
Flash Grafting of Functional Random Copolymers for surface neutralization
F. Ferrarese Lupi, T.J. Giammaria, G. Seguini, M. Ceresoli, M. Perego, D. Antonioli, V. Gianotti, K. Sparnacci and M. Laus.
submitted.
Conferences
EPF2013 European Congress of Polymers, Pisa, June16th-21th 2013.
Stabilization of mixed morphology in Block Copolymer thin films by solvent assisted thermal processing.
Poster presentation
Fabrication of nanostructures by means of block copolymer based lithography
Thank you for your attention.
Monica Ceresoli 15/10/2013
Technologies under study
Residual solvent
Residual solvent locally trapped at the interface between random and block copolymer.
"local" toluene rich interphase.
Toluene amount in the block layer in the absence of random is 0,083 ng mm -2 nm -1 .
Correlation length
SEM images are mapped through a intensity gradient function.
Gradient vector of intensity C. Harrison et al, ,Macromolecules 33, 857-65 Extraction of correlation length ξ correlation function
Optimization of RTP
How to get an effective plateau … setting an overheating in the nominal temperature, the radiative power of infrared lamps can keep the temperature costant.
Time (s) Time (s) This assures control on very short thermal treatments too (from minutes to seconds).
Study of the Early stages of self-assembling evolution in symmetric PS-b-PMMA thin films
Materials and Techniques
Samples preparation
• • • • • Neutralization of the substrate.
Block Copolymer deposition.
Thermal treatment for self-assembling.
Remotion of PMMA Acquisition of images by SEM
Block Copolymer Random Copolymer SiO 2 Si