Surface Morphology Diagram
for Cylinder-Forming Block
Copolymer Thin Films
Xiaohua Zhang
Center for Soft Condensed Matter Physics and Interdisciplinary Research
Soochow University
Background
A
B
Phase diagram for a block copolymer with various structures
Current Solutions
Orientation of Cylinders
•
Needs
- 3D nanostructure Manufacturing
- 3D characterization of nanostructure
- Control of 3D nanostructure
•
200 nm
Y. Gong et al
Macromolecules 2006 39, 3369
200 nm
T. Russell et al
Adv. Mater. 2004 16, 226
T. Russell et al
Langmuir, 2008, 24, 3545
Current Problems
- 2D structures
- Physical Template
Self-assembling Materials for Bottom-up Nanofabrication Processes
Challenges
•Contain defects in many self assembled nanostructures.
• Lack sufficient long-range order for certain nanotechnology applications.
O2 RIE
O2 RIE
CF4 RIE
CF4 RIE
35 nm period
Hitachi Global Storage Technologies
J. Cheng, Nature Materials, 3, 823-828(2004)
Assembly of Block Copolymer Films
Our goal:
• Develop critical measurement solutions that enable nanomanufacturing with guided block
copolymer assembly for next generation magnetic data storage, nanoscale electronics, and
high efficiency membranes for energy.
Method:
•Combine unique modeling platforms with precision thermal processing techniques to
enable the development of small angle x-ray and neutron scattering to measure structural
uniformity, including orientation distributions, and pattern placement in self-assembled
polymer films within templated surfaces.
•Controlling Orientation using
•Metrology of Orientation
Cold Zone Annealing (CZA), sample in Nanostructured Films
preparation procedure and unique
thermal processing technique
•3D Nanostructure for
Cylinder-Forming Block
Copolymer Thin Films
SELECTIVE
REMOVAL OF
ONE OF THE
BLOCKS
RIE
ETCH
3D Nanostructure
Surface Morphology Diagram of PS-PMMA Block Copolymer Films on
Oxide Silicon Substrate
180
160
200nm
7
Perpendicular
6
120
Mixed
100
5
4
80
Parallel
hf / L0
hf / nm
140
Flow Coating
3
60
128
136
144
152
o
160
168
176
2
184
Spin Coating

T/ C
Materials:
Poly (styrene-block-methyl methacrylate)
Mn: PS(35500)-PMMA(12200)
Mw/Mn: 1.04
C. M Stafford et al. Rev. Sci. Instr. 11(2006) 023908-1
Flow Coating without
Residual Solvent
Sample Preparation Procedure Dependence
200nm
Spin-coated in air
Flow-coated in air
Spin-coated in toluene vapor
Spin-coated in toluene vapor &
prebaked prior to annealing
Film thickness:  120 nm
Annealing: 155˚C for 15 h
Prebaking: 93 ˚C for 15 h
Surface Morphology Diagram
200
8.0
180
7.2

6.4

140
5.6

120
4.8
100
4.0
80
3.2
60
2.4
128
136
144
152
o
T/ C
160
168
hf / L0
hf / nm
160
200nm
58nm
71nm
86nm
104nm
130nm
168nm
s
Increasing Film Thickness
PMMA
PS
AFM phase images of flow
coated PS-b-PMMA block
copolymers after annealing at
147 ˚C for 15 h.
3D Characterization of Nanostructure by Neutron Reflectivity (NR)
NCNR in NIST
qx
Incident
neutrons

ki
θ

q
Detector
qz

ko
2

ko
θ

ki

q

ki
θ
Sample

ko
2
θ
2θ
 2
ki 

  
q  ko  ki
10
0.000007
Air
0.000006
Si
0.000005
SLD
1
0.1
0.000004
0.000003
0.000002
0.000001
0.000000
0.01
0
200
400
600
800
Z(Å)
0.001
200nm
0.0001
0.00001
0
0.01
0.02
0.03
0.04
dPS-b-PMMA, 80 nm, 147 oC for 15 h
0.05
0.06
Orientation Distribution Measurement of 3D Nanostructure by RSANS
We convert from beam-coordinates (qx,qy,qz) to
sample-coordinates (Qx,Qy,Qz) using a rotation matrix
Qx  q x cos  q z sin 
Qy  q y
Qz  q x sin   q z cos
Qz
Qy
Qx
Samples show a mix of parallel and perpendicular
cylinder scattering
Low-q scattering
from size disorder
Hexagonal pattern
from laying-down
cylinders
Weak ring from
random component
Scattering peak from
standing-up cylinders
200nm
Film thickness:136nm
Annealing:147ºC for 15h
Content of perpendicular cylinders:80%
Film thickness:141nm
Annealing:165ºC for 15h
Content of perpendicular cylinders:59%
Data was fit by extending the model of Ruland and Smarsly.
Ruland, W.; Smarsly, B. J. Appl. Cryst. 2005, 38, 78-86.
Self-assembly Driving Force of 3D Nanostructure
NR Measurements on Residual Solvent in PS-b-PMMA Films
10
-2
-3
16% Residual Solvent
0.3
0.2
0.1
0.0
10
-4
10
-5
-6
10
0.00
Si
Air
300
600
900
Z(Å)
Flow-Coated Film
0.03
0.06
0
10
-1
10
-2
10
-3
10
-4
10
-5
-6
0.09
0.12
0.15
10
0.00
Volume Fraction
10
-1
Reflectivity
Reflectivity
10
Volume Fraction
10
10
0
12% Residual Solvent
Air
Si
0.3
0.2
0.1
0.0
0
300
600
Z(Å)
900
Spin-coated Film
0.03
0.06
0.09
-1
q(Å )
-1
q(Å )
PS-b-PMMA in deuterated toluene
0.12
PS Film Thickness and Molecular Weight Dependence
1.60
2
100
1.55
0.008
0.010 0.012
-1
q(Å )
0.014
0.016
41 nm
0.01
91 nm
1E-4
208 nm
0.02
0.04
0.06
0.08
0.10
0.12
0.14
1.45
147 nm
-2
0
50
100
150
200
250
d (nm)
1.40
1.30
0.16
0
400
800
1200
1600
2000
Z(Å)
-1
2
1000
Reflectivity
100
10
1
1
 (vol%)
1
Reflectivity
-1
208 nm
q(Å )
100
0
1.35
147 nm
1E-6
0.00
41 nm
91 nm
 (vol%)
-2
0.006
1.50
-6
Reflectivity
0.01
1
1
1
SLD 10 ,(Å )
Reflectivity
100
0.1
0.006
0.008
0.010
0.012
-1
q(Å )
24 kg/mol
0.01
51 kg/mol
97 kg/mol
0
-1
1E-4
818 kg/mol
1E-6
0.00
0.02
0.04
0.06
0.08
-1
q(Å )
0.10
0.12
0.14
-2
0
200
400
600
-1
Mn(kg mol )
800
1000
0.01
0.01
0.006
0.008
0.010
0.012
-2
0.1
0.004
1.14
-6
Reflectivity
1
1E-3
As Cast
One-step
Two-step
1.16
10
1.12
SLD 10 ,(Å )
Reflectivity
1
1.18
As Cast
One-step
Two-step
100
100
0.014
-1
q(Å )
1E-4
1.8
1.5
 (vol%)
PMMA Films
1.2
0.9
0.6
0.3
0.0
One-step
As Cast
Two-step
Thermal History
1.10
1.08
1.06
1.04
1E-6
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0
0.14
200
400
600
800
1000
1200
Z(Å)
-1
q(Å )
NR data (symbols) of as-cast, one-step (93 oC for 15 h) and two-step (93 oC for 15 h followed by 155 oC for another 15 h) annealed
PMMA films with as-cast film thickness of 121 nm at fixed molecular weight (20 kg/mol).
4.0
Reflectivity
1
100
3.5
1
3.0
0.01
0.006
0.008
0.010 0.012
-1
q(Å )
0.014
0.016
69 nm
0.01
 (vol%)
Reflectivity
100
2.5
2.0
1.5
121 nm
1E-4
1.0
169 nm
0.5
1E-6
0.00
201 nm
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.0
60
90
120
150
180
210
-1
q(Å )
d (nm)
NR scans (symbols) measured from the PMMA films of different thickness at fixed molecular weight (20 kg/mol).
FTIR Characterization of Residual Solvent in BCP Films
0.0018
0.0016
Absorbance
0.0014
0.0012
0.0010
Toluene-d8 Peak
0.0008
0.0006
As-cast PMMA
Annealed PMMA
0.0004
Annealed PS
0.0002
Macromolecules 2010, 43, 1117–1123.
ACS Nano, 2008, 2, 2331-2341.
As-cast PS
PS (51kg/mol)
PMMA (20kg/mol)
Film thickness : 160 nm.
0.0000
2360
2340
2320
2300
2280
2260
2240
2220
2200
-1
Wavenumbers(cm )
Samples
PMMA as cast film from 3% d-Toluene solution
Residual solvent concentration (weight)
1.2 ± 0.2 %
PMMA baked and dried in vacuum oven (repeat)
< 0.2%
PS as cast from 3% d-Toluene solution (repeat)
< 0.4%
PS baked and dried in vacuum oven
< 0.4%
The estimation of residual d-toluene concentration is based on its characteristic peak located around 2274 cm-1.
Calibration is made with the area ratio of the strong bands corresponding to d-toluene (2274 cm-1) and PMMA (1730 cm-1)
in the FTIR spectra of 3% polymer solution.
Summary
• Film preparation procedure, and other processing
effects, cannot be ignored in nanomanufacturing
applications.
• Fundamentally demonstrate the interplay between
intrinsic BCP structure and processing conditions.
• R-SANS and NR can deduce orientational distribution in
BCP cylinder thin films.