Surface Morphology Diagram Surface Morphology Diagram for Cylinder-Forming Block for Cylinder-Forming Block

Copolymer Thin FilmsCopolymer Thin Films

Xiaohua Zhang

Center for Soft Condensed Matter Physics and Interdisciplinary ResearchCenter for Soft Condensed Matter Physics and Interdisciplinary Research

Soochow UniversitySoochow University

Phase diagram for a block copolymer with various structures

Current Solutions

• Needs - 3D nanostructure Manufacturing - 3D characterization of nanostructure - Control of 3D nanostructure• Current Problems - 2D structures - Physical Template

200 nm 200 nm

Y. Gong et al Macromolecules 2006 39, 3369

T. Russell et al Adv. Mater. 2004 16, 226

Background

A B

Orientation of Cylinders

T. Russell et al Langmuir, 2008, 24, 3545

Challenges•Contain defects in many self assembled nanostructures. • Lack sufficient long-range order for certain nanotechnology applications.

O2 RIE

CF4 RIE

J. Cheng, Nature Materials, 3, 823-828(2004)

O2 RIE

CF4 RIE

35 nm period

Hitachi Global Storage Technologies

Self-assembling Materials for Bottom-up Nanofabrication ProcessesSelf-assembling Materials for Bottom-up Nanofabrication Processes

Assembly of Block Copolymer FilmsAssembly of Block Copolymer FilmsOur 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 Cold Zone Annealing (CZA), sample preparation procedure and unique

thermal processing technique

•Metrology of Orientation in Nanostructured Films

•Metrology of Orientation in Nanostructured Films

•3D Nanostructure for Cylinder-Forming Block Copolymer Thin Films

SELECTIVE REMOVAL OF ONE OF THE

BLOCKS

RIE ETCH

SELECTIVE REMOVAL OF ONE OF THE

BLOCKS

RIE ETCH

128 136 144 152 160 168 176 184

60

80

100

120

140

160

180

2

3

4

5

6

7

hf / L

0

Parallel

Mixed

Perpendicular

hf /

nm

T / oCSpin Coating

Flow Coating without Residual Solvent

3D Nanostructure3D Nanostructure

Flow Coating

200nm

C. M Stafford et al. Rev. Sci. Instr. 11(2006) 023908-1

Materials:Poly (styrene-block-methyl methacrylate) Mn: PS(35500)-PMMA(12200) Mw/Mn: 1.04

Surface Morphology Diagram of PS-PMMA Block Copolymer Films on Surface Morphology Diagram of PS-PMMA Block Copolymer Films on Oxide Silicon SubstrateOxide Silicon Substrate

200nm

Film thickness: 120 nmAnnealing: 155˚C for 15 h Prebaking: 93 ˚C for 15 h

Spin-coated in air Flow-coated in air

Spin-coated in toluene vapor Spin-coated in toluene vapor & prebaked prior to annealing

Sample Preparation Procedure DependenceSample Preparation Procedure Dependence

128 136 144 152 160 16860

80

100

120

140

160

180

200

2.4

3.2

4.0

4.8

5.6

6.4

7.2

8.0

hf / L

0

hf /

nm

T / oC

Surface Morphology DiagramSurface Morphology Diagram

AFM phase images of flow coated PS-b-PMMA block copolymers after annealing at 147 ˚C for 15 h.

s

PMMA

PS

Increasing Film Thickness

58nm 71nm

104nm 130nm 168nm

86nm

200nm

ik

okq

θ θ

Incidentneutrons

Detector

Sample

2 q

ik

ok

ok

ik

θ θ

2

qx

qz

io

i

kkq

k

2

2θ

3D Characterization of Nanostructure by Neutron Reflectivity (NR)3D Characterization of Nanostructure by Neutron Reflectivity (NR)

NCNR in NIST

dPS-b-PMMA, 80 nm, 147 dPS-b-PMMA, 80 nm, 147 ooC for 15 hC for 15 h

200nm

0 200 400 600 8000.000000

0.000001

0.000002

0.000003

0.000004

0.000005

0.000006

0.000007

Z(Å)

SL

D

Air Si

We convert from beam-coordinates (qx,qy,qz) to sample-coordinates (Qx,Qy,Qz) using a rotation matrix

Orientation Distribution Measurement of 3D Nanostructure by RSANS Orientation Distribution Measurement of 3D Nanostructure by RSANS

cossin

sincos

zxz

yy

zxx

qqQ

qQ

qqQ

Qy

Qx

Qz

Samples show a mix of parallel and perpendicular cylinder scattering

Hexagonal pattern from laying-down cylinders

Scattering peak from standing-up cylinders

Low-q scattering from size disorder

Weak ring from random component

Annealing:147ºC for 15h

Content of perpendicular cylinders:80%

Film thickness:136nm

200nm

Annealing:165ºC for 15h

Content of perpendicular cylinders:59%

Film thickness:141nm

Data was fit by extending the model of Ruland and Smarsly.Ruland, W.; Smarsly, B. J. Appl. Cryst. 2005, 38, 78-86.

0.00 0.03 0.06 0.09 0.12 0.1510-6

10-5

10-4

10-3

10-2

10-1

100

q(Å-1)

Re

fle

cti

vit

y

Flow-Coated Film

300 600 9000.0

0.1

0.2

0.3

Vo

lum

e F

racti

on

Air Si

Z(Å)

16% Residual Solvent

10-6

10-5

10-4

10-3

10-2

10-1

100

0.00 0.03 0.06 0.09 0.12

Spin-coated Film

Re

fle

cti

vit

yq(Å-1)

0 300 600 9000.0

0.1

0.2

0.3

Z(Å)

Vo

lum

e F

ract

ion

Air Si12% Residual Solvent

PS-b-PMMA in deuterated toluene

NR Measurements on Residual Solvent in PS-b-PMMA Films NR Measurements on Residual Solvent in PS-b-PMMA Films

Self-assembly Driving Force of 3D NanostructureSelf-assembly Driving Force of 3D Nanostructure

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.141E-6

1E-4

0.01

1

100

51 kg/mol

818 kg/mol

97 kg/mol

24 kg/mol

Re

fle

cti

vit

y

q(Å-1)

0.006 0.008 0.010 0.012

0.1

1

10

100

1000

Re

fle

cti

vit

y

q(Å-1)

0 200 400 600 800-2

-1

0

1

2

(v

ol%

)

Mn(kgmol-1)

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.161E-6

1E-4

0.01

1

100

147 nm

208 nm

91 nm

41 nm

Re

fle

cti

vit

y

q(Å-1)

0.006 0.008 0.010 0.012 0.014 0.016

0.01

1

100

Re

fle

cti

vit

y

q(Å-1)

0 400 800 1200 1600 20001.30

1.35

1.40

1.45

1.50

1.55

1.60

147 nm

Z(Å)

SL

D1

0-6,(

Å-2)

41 nm

91 nm

0 50 100 150 200 250-2

-1

0

1

2

(v

ol%

)

d (nm)

208 nm

PS Film Thickness and Molecular Weight Dependence PS Film Thickness and Molecular Weight Dependence

1E-6

1E-4

0.01

1

100

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14

0.004 0.006 0.008 0.010 0.012 0.0141E-3

0.01

0.1

1

10

100

1000

Re

fle

cti

vit

y

q(Å-1)

As Cast

One-step Two-step

Re

fle

cti

vit

y

q(Å-1)

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).

60 90 120 150 180 2100.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

(v

ol%

)

d (nm)

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.161E-6

1E-4

0.01

1

100

169 nm

201 nm

121 nm

69 nm

Re

fle

cti

vit

y

q(Å-1)

0.006 0.008 0.010 0.012 0.014 0.016

0.01

1

100

Re

fle

cti

vit

y

q(Å-1)

NR scans (symbols) measured from the PMMA films of different thickness at fixed molecular weight (20 kg/mol).

PMMA FilmsPMMA Films

0 200 400 600 800 1000 1200

1.04

1.06

1.08

1.10

1.12

1.14

1.16

1.18 As Cast

Z(Å)

SL

D1

0-6,(

Å-2)

One-step

0.0

0.3

0.6

0.9

1.2

1.5

1.8

(v

ol%

)

Thermal HistoryOne-stepAs Cast Two-step

Two-step

FTIR Characterization of Residual Solvent in BCP FilmsFTIR Characterization of Residual Solvent in BCP Films

Samples Residual solvent concentration (weight)

PMMA as cast film from 3% d-Toluene solution 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.

220022202240226022802300232023402360

0.0000

0.0002

0.0004

0.0006

0.0008

0.0010

0.0012

0.0014

0.0016

0.0018

Toluene-d8 Peak

Annealed PS

As-cast PS

Annealed PMMA

As-cast PMMA

Wavenumbers(cm-1)

Ab

sorb

ance

PS (51kg/mol) PMMA (20kg/mol) Film thickness : 160 nm.

Macromolecules 2010, 43, 1117–1123.ACS Nano, 2008, 2, 2331-2341.

• Film preparation procedure, and other processing effects, cannot be ignored in nanomanufacturing applications.

• Fundamentally demonstrate the interplay between interplay between intrinsic BCP structure and processing conditionsintrinsic BCP structure and processing conditions.

• R-SANS and NR can deduce orientational distribution orientational distribution in BCP cylinder thin films.

SummarySummary