Fabrication of nanostructures by means of

Block Copolymer based lithography

Monica Ceresoli

Supervisor: Prof. Paolo Milani

Co-Supervisor: Dr. Michele Perego

Introduction

Implementation of self-assembling materials in Microelectronics lithography.

ITRS 2011 Edition: “Emerging Research Materials”

200390 nm

200565 nm

200745 nm

200932nm

201122 nm

201314 nm

201510 nm

Manifacturing Development Research

Fabrication issue: sub 20 nm structures

Requirements:•High density•Long range order•Simple and short process

BLOCK COPOLYMERS (BCP): class of macromolecules produced by covalently bonding two or more chemically distinct polymer blocks.

Thermal treatment Thermal treatment

Introduction

I.Botiz et al., Materials Today 13, 42-51 (2010), F. S. Bates et al., Physics Today 52, 32-38 (1999)

Lamellae

Thermodynamic Incompatibility +

Covalent Bond

Phase separation in ordered nano-domains

IntroductionLithographic application of Lamellar thin films.

Requirements:•High density•Long range order•Simple and short process

R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162, R. Ruiz et al., Adv. Mater. 19, 587–591 (2007)

Furnace100 minutes

Annealing temperature (°C) Annealing time (min)

Corr

elati

on le

ngth

ξ (n

m)

Corr

elati

on le

ngth

ξ (n

m)

Problems:•Long time process.•Weak dependence on Temperature and time of annealing.•Small dimension of ordered domains (correlation length ξ)

IntroductionLithographic application of Lamellar thin films.

Requirements:•High density•Long range order•Simple and short process

R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162, R. Ruiz et al., Adv. Mater. 19, 587–591 (2007)

New study:Thermodynamics on short time-scale

Problems:•Long time process.•Weak dependence on Temperature and time of annealing.•Small dimension of ordered domains (correlation length ξ)

Materials and Techniques Preparation of lamellar thin films.

Si

SiO2

Random Copolymer

• Neutralization of the substrate.

Materials and Techniques Preparation of lamellar thin films.

Si

SiO2

Random Copolymer

• Neutralization of the substrate.

• Block Copolymer deposition.

Poly (Styrene-block-Methyl Methacrylate)

50% PS 50% PMMA

Block Copolymer

Materials and Techniques Preparation of lamellar thin films.

Si

SiO2

Random Copolymer

• Neutralization of the substrate.

• Block Copolymer deposition.

Block Copolymer

• Thermal treatment.

Materials and Techniques

F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601

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!

80 100 120 140 1600

20

40

60

80

100

120

140

160

180

200

220

240

260

Tem

pera

ture

(°C)

Time (s)He

ating

ram

p

Steady state

Cooling ramp

Samples are heated by halogen lamps irradiation.

• Fast heating and cooling ramp.• Real time –control of sample temperature.• Temperatures up above 300°C.

Increasing the annealing temperature more and more ordered films get formed.

Experimental Results 60

s of

ann

ealin

g

Temperature

M. Ceresoli et al., 2013, submitted.

Experimental Results

Temperature (°C)

60s treatment10s treatment

M. Ceresoli et al., 2013, submitted.

Significant variations of the correlation length (ξ) have been observed.

Experimental Results

Temperature (°C)

100 minutes conventional furnace

1minute in RTP time of process reduced

by two orders of magnitude

?

60s treatment10s treatment

R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162

Two times higher ξ in respect to literature results.

Experimental Results

R. Ruiz et al., Adv.Mater. 2007,19, 587-591, S. Ji, P.F. Nealey et al., Macrom. (2011) 44.4291.

time (s)

290°C270°C250°C

RTP

290°

C

Time of annealing

1s 5s 10s 60s 5m 15m

Corr

elati

on le

ngth

ξ (n

m)

Experimental Results

100 nm

FFT

A double phase appears!

100 nm

Selective remotion of PMMA phase

Residual solvent at the interface with the substrate

F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601

Experimental Results

On courtesy of Prof. M. Laus, Università del Piemonte Orientale

1 10 100 1000Time (s)

290°C

RTP

290°

C

1s

Time of annealing

Time (s)

Solvent content

5s 10s 60s 5m 15m

cylinders drive order

Corr

elati

on le

ngth

ξ (n

m)

Perspectives and Open PointsMorphology investigation with Grazing Incident Small Angle X-ray Scattering.

Analysis in progress…

Perspectives and Open PointsThe presence of a double phase is affected by solvent choise…

Boili

ng T

empe

ratu

re o

f sol

vent

Toluene

20 nm

?

ChloroformAcetone

1min, 250°C, RTP20 nm

THF

PS selectivePMMA selective

Perspectives and Open PointsIn very fast thermal treatment, heating and cooling ramps become relevant…

0 10 20 30 40 5040

45

50

55

60

65

70

Cor

rela

tion

leng

ht (

nm)

Heating rate (°C/s)

• No significant variation for steady state as long as 30 s.• What about 5 s or 1 s of steady state?

80 100 120 140 1600

20

40

60

80

100

120

140

160

180

200

220

240

260

Tem

pera

ture

(°C)

Time (s)

Heati

ng ra

mp

Steady state

Cooling ramp

Heating rate (°C/s)Co

rrel

ation

leng

th (n

m)

Pubblications

Conferences

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.

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

Thank you for your attention.

Monica Ceresoli 15/10/2013

Fabrication of nanostructures by means of block copolymer based lithography

Technologies under study

Residual solventResidual solvent locally trapped at the interface between random and block copolymer.

Toluene amount in the block layer in the absence of random is 0,083 ng mm-2nm-1.

"local" toluene rich interphase.

Correlation lengthSEM images are mapped through a intensity gradient function.

C. Harrison et al, ,Macromolecules 33, 857-65

Gradient vector of intensity

Extraction of correlation length ξ

correlation function

How to get an effective plateau … setting an overheating in the nominal temperature, the radiative power of infrared lamps can keep the temperature costant.

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

80 100 120 140 1600

20

40

60

80

100

120

140

160

180

200

220

240

260

Te

mp

era

ture

(°C

)

Time (s)

80 100 120 140 1600

20

40

60

80

100

120

140

160

180

200

220

240

260

80 100 120 140 1600

20

40

60

80

100

120

140

160

180

200

220

240

260

Te

mp

era

ture

(°C

)

Time (s)

80 100 120 140 1600

20

40

60

80

100

120

140

160

180

200

220

240

260

Optimization of RTP

Materials and Techniques Samples preparation

Si

SiO2

Random Copolymer

• Neutralization of the substrate.• Block Copolymer deposition.

Block Copolymer

• Thermal treatment for self-assembling.• Remotion of PMMA• Acquisition of images by SEM