Fabrication of nanostructures
by means of
Block Copolymer based lithography
Monica Ceresoli
Supervisor: Prof. Paolo Milani
Co-Supervisor: Dr. Michele Perego
Introduction
2003
2005
2007
2009
2011
2013
2015
90 nm
65 nm
45 nm
32nm
22 nm
14 nm
10 nm
Manifacturing
Development
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:
Furnace
100 minutes
Annealing temperature (°C)
Correlation length ξ (nm)
Correlation length ξ (nm)
• 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
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
SiO2
Si
Materials and Techniques
Preparation of lamellar thin films.
• Neutralization of the substrate.
• Block Copolymer deposition.
Block Copolymer
Random Copolymer
SiO2
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
SiO2
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: • Fast heating and cooling ramp.
• Real time –control of sample temperature.
Seconds!
• Temperatures up above 300°C.
Steady state
260
Temperature (°C)
240
220
200
180
160
140
120
100
80
60
40
20
0
Samples are heated by halogen lamps irradiation.
F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601
80
100
120
Time (s)
140
160
Experimental Results
60s of annealing
Increasing the annealing temperature more and more ordered films get formed.
Temperature
M. Ceresoli et al., 2013, submitted.
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.
60s treatment
10s treatment
100 minutes
conventional furnace
1minute in RTP
time of process reduced
by two orders
of magnitude
?
Temperature (°C)
R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162
Experimental Results
5s
10s
60s
RTP 290°C
1s
Correlation length ξ (nm)
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.
5m
15m
Experimental Results
A double phase appears!
Selective remotion of PMMA phase
100 nm
Residual solvent
at the interface with the substrate
100 nm
F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601
Experimental Results
5s
10s
60s
15m
5m
RTP 290°C
1s
Correlation length ξ (nm)
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
Time (s)
1000
Perspectives and Open Points
Morphology investigation with Grazing Incident Small Angle X-ray Scattering.
Analysis
in progress…
Perspectives and Open Points
Boiling Temperature of solvent
The presence of a double phase is affected by solvent choise…
?
Toluene
PS selective
PMMA selective
20 nm
Acetone
20 nm
Chloroform
1min, 250°C, RTP
THF
Perspectives and Open Points
In very fast thermal treatment, heating and cooling ramps become relevant…
length
Correlation
Correlation lenght
(nm)(nm)
Temperature (°C)
70
Steady state
260
240
220
200
180
160
140
120
100
80
60
40
20
65
60
55
50
45
40
0
80
100
120
140
160
0
Time (s)
• 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)
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-2nm-1.
Correlation length
SEM images are mapped through a intensity gradient function.
Gradient vector of intensity
correlation
function
Extraction of correlation length ξ
C. Harrison et al, ,Macromolecules 33, 857-65
Optimization of RTP
260
260
240
240
220
220
200
200
Temperature (°C)
Temperature (°C)
How to get an effective plateau … setting an overheating in the nominal temperature,
the radiative power of infrared lamps can keep the temperature costant.
180
160
140
120
100
180
160
140
120
100
80
80
60
60
40
40
20
20
0
0
80
100
120
Time (s)
140
160
80
100
120
140
160
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
SiO2
Si