Nanometrology: enabling applications of nanotechnologyC GourgonC Gourgon, LTM-CNRS GrenobleCNRS...

Nanometrology: enabling applications Nanometrology: enabling applications of nanotechnology

C M Sotomayor Torres*, T Kehoe,C M Sotomayor Torres , T Kehoe, N Kehagias, V Reboud, D Dudek

*ICREAPhononic and Photonic Nanostructures Groupp

Catalan Institute of Nanotechnology (CIN2-CSIC)Barcelona SPAIN

1Trends in Nanotechnology, 10th September 2010, Braga, Portugal

Collaborators & Support

J Bryner, J Vollman, J Dual, C Mechanics, ETH, Zurich

S Landis, CEA, LETI , Grenoble

C Gourgon LTM CNRS GrenobleC Gourgon, LTM-CNRS Grenoble

S Arpiannen, J Ahopelto, VTT Espoo, Finland

W Khunsin, S G Romanov, A Amann, E P O’Reilly, G Kocher

R Zentel, U Mainz

S Pullteap and H C Seat, ENSEEIHT, Toulouse


Outline

1. Introduction

2. Nanometrology for Nanoimprintlithography:g p y

a. Sub-wavelength diffraction

b Photoacoustic metrologyb. Photoacoustic metrology

3. Nanometrology for Self-assembly

a. Opposite partners/ elements

b. Rotational diffraction

4. Conclusions


Nanometrology and Nanotechnology

• Critical to enable the industrial uptake of nanotechnology

• Necessary to measure:

– Product characteristics device performance toxicologyProduct characteristics, device performance, toxicology (potential public health risks), product lifetime, security

• Requirements for manufacturable technology• Requirements for manufacturable technology

– Standardisation, regulation – repeatable and universal

– Easy to operate

– Developed in coordination with manufacturing techniquesp g q

• Integrated, in-line, real-time, advanced process control• Relevant measurands


Nanometrology Challenges

• Miniaturisation – things are getting smaller

• Heterogeneous integration – things are getting more complex

– 3rd Dimension increasingly used– Dimensions and material properties

• Insufficient standardisation of techniques or reference samplessa p es

• Existing methods are slow, often destructive and not optimised for 3Doptimised for 3D


Metrology challenges for Nanofabrication

• Critical dimension measurement < 50 nmS i d t lith h d 32 (2011)

Intel SRAM

Semiconductor lithography node 32 nm (2011)Critical dimensions and physical properties

45nm

• 3D StructureComplex: Typical of heterogeneous integration, interconnects

• In-situ, inline, real-time

S. Landis et al, Nanotechnology (2006) B.Chao, Proc SPIE 6921 (2008)Ye et al, Langmuiir 22 7378 (2006).3D Photonic crystal in Si


, ,Advanced Process Control of systematic drift and process behaviour

Metrology techniques for nanoscale – limitations

• SEM For height, slope, profile, requires destructive cross sectiondestructive cross-section.

• AFM Difficult to access sidewalls, corners, l ti l l

1m

A.E. Vladar et al, Proc SPIE 69220Hrelatively slow

• TEM Resolution ~ 0.1 nm.

Destructive, slow

• X-ray Imaging Requires synchrotron x-ray B.C. Park et al, Proc. SPIE 651819X ray Imaging Requires synchrotron x ray source

• Optical Scatterometry• Optical Scatterometry

Wi t h N T h l Ltd

Requirement of wavelength, polarization or angle variability.


C. David et al, Proc. MNE 2008

Wintech Nano-Technology Ltd

Nanoimprint Lithography (NIL)

Advantages

• Resolution (sub 10 nm)Stamp (Si, Quartz, etc)

Resist (polymer monomer) Resolution (sub 10 nm)• Fast (sec/cycle)• Low cost ($0.2M vs $25M)• Simple

Substrate Resist (polymer, monomer)

mp• Flexible (UV, heat)

Applications

Imprint (Pressure +heat or UV light)

• Semiconductors• Optics• Bio

Release(cool down )

Bio• Organic electronics• Sensors

Hi h l ti C l tt F ti l d i

RIE of residual layer

High resolution Complex patterns Functional devices


N.Kehagias, Nanotechnology 18 (2007) V.Reboud, Jpn. J. Appl. Phys., 47 (2008)

Sub-wavelength diffraction metrology

• Test structures of blazed gratings asymmetric diffraction pattern

• Individual lines < diffraction limit Groups of lines > diffraction limit• Individual lines < diffraction limit. Groups of lines > diffraction limit

• Sub-wavelength features in grating eg Line-width, height, defects, sidewall angle, curvature. Linewidths: 50, 100, 150, … 350nm

• Defects affect relative intensity of diffraction orders in far-field

• Suitable for transparent or opaque structures

• Non-destructive, Fast collection of data

Gap 58 nm on In

tens

ity

-2 -1 0 +1 +2Gap 58 nm

Diff

ract

iLine 53 nm

1 m


T. Kehoe et al, Proc. SPIE 69210F, 2008

Modelling of Sub-wavelength diffraction

• Rigorous Coupled Wave Analysis (RCWA) 4.0

4.5

n

Height( )

• Finite difference time domain (FDTD) 2.0

2.5

3.0

3.5

ve d

iffra

ctio

nffi

cien

cy

+first/-first

0.0

0.5

1.0

1.5

0.07 0.08 0.09 0.10 0.11 0.12 0.13

Rel

ativ ef

first/ first

+first/+second500nm

line height/ um

Width20

25

units

)

FDTD vs. RCWA normalised to first order

FDTDRCWA

4.0

5.0

6.0

ract

ion

cy

+first/-first+first/+second

10

15

20

(arb

itrar

y RCWA

1.0

2.0

3.0

elat

ive

diff

ref

fici

enc

0

5

10

Effic

ienc

y


0.00.00 0.01 0.02 0.03 0.04 0.05 0.06

Re

Line width increase / um

-3 -2 -1 0 1 2 3

E

Diffracted Orders

Sub-wavelength diffraction measurement system

Laser• In-line design • Sub wavelength diffraction

Sample

• Sub-wavelength diffraction metrology with surface imaging by microscope optics

SampleCCD A –diffraction patternz x

y

Microscope objective

• Enables centring of the laser spot on the gratings

j

CCD B –image of surface

250

150

200

250

bitr

ary

uni

ts +1

50

100

nten

sity

/ ar

b

-2

-1

+2


25 m0

0 200 400 600 800 1000 1200 1400

In

Pixels

Sub-wavelength – Detection of defects

1

1.2

au

Measured (+1/-1) = 2.85Simulated (+1/-1) = 2.68

• Defect detection– missing 50 nm & 100 nm lines

0.6

0.8

n Ef

ficie

ncy

/

• Agreement between simulated and measured diffraction efficiencies

0

0.2

0.4

Diff

ract

ion

Simulated 0.6

0.8

1

1.2

n ef

ficie

ncy

/au

No Defect (RHS/LHS) = 2.59

Defect (RHS/LHS) = 1.44

0-3 -2 -1 0 1 2 3

Diffraction Order0

0.2

0.4

-3 -2 -1 0 1 2 3

Diff

ract

ion

1 m0 8

1

1.2

cy /

au

No defect (RHS/LHS)= 3.53Defect (RHS/LHS) =2 11

Measured

Diffraction Orders

0.2

0.4

0.6

0.8

Diff

ract

ion

efic

ienc 2.11


100 nm 50 nm

0-3 -2 -1 0 1 2 3

Diffraction Order T. Kehoe, Microelec. Eng. 86 (2009)

Sub-wavelength – Detection of defects

Line 53

Gap 58 nm• Grating stamps made with average line-width from 193 –214 nm

1 m

Line 53 nm • Measured and modelled diffraction efficiencies (1st & 2nd

order) decrease with increasing line-width, by approximately 5% per 5 nm

1/ 2 l ti diff ti ffi i d t

-2 Simulated on

• +1/+2 relative diffraction efficiency decreases at approximately 4% per 5 nm

3

on E

ffic

ienc

y -2 Simulated-1 Simulated+1 Simulated+2 Simulated-2 Measured-1 Measured

1 M d

1.1

Diff

ract

io

+1/+2Simulated

+1/+2M d

1

2

zd D

iffra

ctio +1 Measured

+2 Measured 1

d R

elat

ive

Effic

ienc

y Measured

0195 200 205 210 215

Nor

mal

iz

0.9195 200 205 210 215

Average Linewidth / nmorm

aliz

ed E


95 00 05 0 5

Average Linewidth / nm

g

No

T. Kehoe, NNT 08 conference, Kyoto, Japan

Diffraction from 3D Structures

• Polymer relaxes and partially reflows, creating rounded line profiles• Measured diffracted order intensities• Measured diffracted order intensities before and after reflowing of the lines

Comparison of measured and simulated diffraction intensities for imprinted lines and reflowed lines


T. Kehoe, NNT 2010, Copenhagen, Denmark

Key steps for NIL – Polymer physical properties

1. Stamp fabrication Imprint (Pressure +heat or UV light)

2. Imprinting process: Temp, Pressure, UVGlass transition temperature, ViscosityGlass transition temperature, Viscosity

3. Demoulding: Mechanical strength Y ´ d l P i ’ ti Young s modulus, Poisson’s ratioAdhesion / anti-sticking coating f

Release (cool down )

surface energy

4. Etching: Polymer etch resistancetc g o y e etc es sta ce

At nanoscale values may changeRIE of residual layer


Photoacoustic Metrology

• Thickness measurements, resolution ~10 nm

• Acoustic scattering from interfaces changes surface reflectivity• Acoustic scattering from interfaces changes surface reflectivity

• Acoustic speed Physical parameters – Modulus, Poisson’s

P P b L 70 f 810 Ti l ti 0 1• Pump-Probe Laser, 70 fs, = 810 nm, Time resolution 0.1 ps

Partial Reflection from interfaces

Propagating acoustic waves

Pump: 70fs laser pulse

Probe: Optical reflectivity change at y gsurface

Laser absorption / generation


Al Polymer Sip g

of thermal stress – acoustic wave

One-dimensional photoacoustic model

• Finite Element Simulation, including viscoelastic damping• Measurement R + Thickness (Ellipsometry) + Optical / Physical

properties (absorption, density) Thermomechanical model

S laser power σexcit stress, T temperature, ε strain z deptht time

attenuation F sensitivityΔR reflectivity change


Photoacoustic Metrology of Nanoimprint Polymers

336 nm PMMA• Nanoimprint polymers13 – 586 nm thick layers

ity c

hang

e

13 586 nm thick layers• Damping in polymer not excessive• Good acoustic impedence

Ref

lect

ivi

R

difference Strong signal • Top interface: Al/polymer• Bottom interface: polymer/Si

Time / ps

• Bottom interface: polymer/Si• FilmThickness compared to ellipsometry and profilometry

ness

/ nm• Physical parameters calculated using

Finite Element model c E

Thic

kncp (m/s)

E (GPa)

kg/m3)

mr-I PMMA 2603 3.2 0.4 1012


time of flight

Time / ps

mr-NIL 6000 2504 2.95 0.4 1008J. Bryner, 2007 IEEE Ultrasonics Symposium, 2007 p 1409

Nanoscale Effects

• Acoustic speed and Young’s modulus increase below 80 nm

• Acoustic speed (c ) increases by 12%• Acoustic speed (cp) increases by 12%

• Young’s modulus (E) increases by 26% at 13 nm.

P i l f HMDS (H th ldi il ) dd d ll i• Primer layer of HMDS (Hexamethyldisilazane) added smaller increases

• Increase probably due to interface effects rather than confinementi dAcoustic speed

2500

3000

3500

/ m

/s

5

6

/ GPa

Young’s modulus

1000

1500

2000

2500

stic

spe

ed

PMMA2

3

4

's M

odul

us

PMMA

0

500

1000

0 20 40 60 80 100 120 140

Aco

us PMMA withHMDS

0

1

2

0 20 40 60 80 100 120 140

Youn

g' PMMA

PMMA with HMDS


Thickness / nm0 20 40 60 80 100 120 140

Thickness / nmT. Kehoe, Proceedings of SPIE Vol. 6921 (2008)

Raised Temperature Measurements

90 deg• Investigation of physical properties approaching glass transition temperature, Tgapp oac g g ass t a s t o te pe atu e, g

• Acoustic speed inversely proportional to thickness

• Close to Tg increase of noise due to buckling of aluminium


Examples of self-assembled structures

Block

10 nmVTT Protein crystals

Block copolymer nanophase separation


separation

3D periodic structures: eg. photonic crystals

Layer-by-layer MicroassemblyAutocloning

S Y Lin Sandial Lab 1998 K Aoki Semicon Lab 2003S Y Lin, Sandial Lab, 1998 K. Aoki, Semicon Lab, 2003

Holography Direct laser writing Artificial Opals

S Kawakami, Tohoku, 1997


K. Aoki, Semicon Lab, 2003 M. Deubel, Karlsruhe, 2004 Tyndall/ICN-CIN2

FCC colloidal crystals: Improving structural order

Equilibriumcrystallisation

Fast crystallisation Reduce interaction with substrate-> reduce crack

Shear force to improvecrystal ordering

Improved quality using acoustic noise


Acoustic vibration

A .Amman et al Proc. SPIE Vol. 6603, 660321 (2007)

Quantifying order in self-assembly

• Define scaleM k h tibl ith i ti th d t l t• Make approach compatible with existing methods or at least acceptable

• In-line or a posteriori?p• Reliable?• Suitable for a standard?

2 μm

L = 0 dB L = 20 dB L = 30 dB L = 40 dB


L = 20 dB is calibrated to water displacement of 2.5 μm

Concept of “opposite beads”

p(r) – probability of finding an opposite beads within a radius r, for a given tolerance parameter ε for the exact location of g p

the spheresAt sphere ‘A’

ε , ( ) ( )( )

( )A B C r AB AB AC

p rAB

( )A B r AB

1 if R

1( )

0y

if R yR

else

)()()(

)(rN

rprNrp

AA

AAAGlobal sum: weighted average


Conditions met by p(r)

• Scalar quantity (dependence on certain predefined orientation undesirable)orientation undesirable)

• Integral measure of a locally observable quantity

• Based on actual position of sphere (not on pixel representation of SEM image: contrast & focus dependent)dependent)

• Robust against missing spheres.

Perfectly ordered system0 04 ( ) 1 00 Th

( ) ( )( ) 1A A AN r p r

p r 0.04 ( ) 1.00p r

0.06 ( ) 0.46p r

Theory

Experiment


( ) 1( )A A

p rN r

( )pExperiment

SEM Characterisation

SEM images of size 65 μm x 40 μm (resolution: 3072 x 2304 pixels)

substrateDrawingdirection

Opal

Position (P)Position (P)


Stochastic-resonance in photonic crystal growth

D = 368 nmr = 5.5 μm ≈ 15D, and ε = 43 nm ≈ 0.12D

P7P7

P10

Position (P)


Position (P)

3 D ordering - Experimental approach

3D analysis2D analysis

θ – incident angleSEM images


gφ – azimuth angle

SEM images

Transmission spectra

22* (1 i ( )d

Bragg’s LawX

U(111)

(002)

(1 11)22* (1 sin ( )eff hkl hkln d

L

WU

Xг

(111)

(200) K (020)

L'

(200)

(11 1)

K ( )


W.Khunsin, Adv. Funct. Mater. 18 (2008)

Rotational symmetry of T(φ)

Without NoiseNoise

X (002)

L

U(111)

(111)

( )

(1 11)

L

WU

Xг

(200) K (020)

L' (111)

Noise


W Khunsin et al, J. Nonlinear Optical. Physics & Materials 17 97 (2008)

Noise Susceptibility: lattice planes dependency

WithoutNoise

10x 5xWithWithNoise


(311) (220) (111)

Conclusions

• New methods presented to characterise nanostructures fabricated by N i i t Lith h (NIL) d lf blNanoimprint Lithography (NIL) and self-assembly.

• Sub-wavelength diffraction found sensitive to defects, line-width and fprofile

– This is potentially in-line metrology method.

• Photoacoustic metrology demonstrated suitable for dimensional and physical measurement of printed structures

• We propose a robust and generic approach to analyse quantitatively two-dimensional lattice ordering.– Opposite partners

– Rotational diffraction symmetry


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Nanometrology: enabling applications of nanotechnologyC GourgonC Gourgon, LTM-CNRS GrenobleCNRS...

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