Science and Technology of Ultrananocrystalline Diamond Films for Multifunctional … ·...

Micro and Nanomechanics LabDepartment of Mechanical Engineering

Science and Technology of Science and Technology of UltrananocrystallineUltrananocrystallineDiamond Films for Multifunctional MEMS/NEMSDiamond Films for Multifunctional MEMS/NEMS

H.D. Espinosa

Acknowledgments: NSF-NIRT

U.S. – South America Workshop:Mechanics and Advanced Materials Research and Education

Rio De Janeiro, Brazil, August 2-6, 2004


OutlineOutlineNIRT Project OverviewFilm Deposition and CharacterizationIdentification of Mechanical PropertiesMultiscale Modeling starting from Quantum MechanicsApplications:

AFM PotentiometryMolecular Writing and Self AssemblyNEMS, e.g., nanoresonators


Participating Institutions/OverviewParticipating Institutions/Overview


UltrananocrystallineUltrananocrystalline Diamond Films For Diamond Films For Multifunctional MEMS/NEMS DevicesMultifunctional MEMS/NEMS Devices

Why UNCD?H.D. Espinosa, Z. Chen, T. Belytschko, M. Hersam, G. Schatz, O. Auciello and M. Moldovan

Extremely high wear resistant (10,000 times longer than Si)

Very low friction coefficient (0.03-0.04 in air)

Very resistant to chemical corrosion

Low threshold, stable field electron emission (~2-3 V/µm)

Broad optical transparency

Highest thermal conductivity (2 x 103 W/m/ K)

Very high elastic modulus (965 GPa)Extreme mechanical hardness (~97 GPa)

Applications

Massively parallel AFM potentiometry

Nanoresonators• Mass Sensors• Wireless Communication• Bio-sensors• …

ραϖ

12

2 EtL

=


Film DepositionFilm DepositionOrlando Orlando AucielloAuciello and John Carlisle (ANL)and John Carlisle (ANL)


iPlasiPlas Microwave Plasma CVD System at ANLMicrowave Plasma CVD System at ANL

OES of Ar/CH4 Plasma

200 400 600 800 1000 1200

C2- Main species forthe growth of UNCD

C2 emission

Inte

nsity

(a.u

.)Wavelength (nm)

Typical Ar/CH4 Plasma

2CH4 → C2H2 +3H2

C2H2 → C2 + H2

CH4 + Ar + H2 = 100 sccm

CH4 = 1 sccm; Ar = 95-99 sccm

100 Torr; 1200 WUNCD Growth Rate:0.15 ~ 0.2 µm/hr (400oC)0.25 ~ 0.3 µm/hr (800oC)

D. Gruen, “Nanocrystalline Diamond Films,” Annu. Rev. Mater. Sci., Vol. 29, pp. 211-259, (1999).

Seeding


Grain Size vs. Grain Size vs. ArAr RatioRatio

Grain size as a function of the Ar ratio: (a) 40%, (b) 60%, (c) 97%, (d) 99%.

D. Zhou et. al., J. Appl. Phys., Vol. 84, pp 1981-1989, (1998).

Raman Spectra shows the Raman Spectra shows the diamond band is broadeneddiamond band is broadened


Grain Size vs. NGrain Size vs. N22 RatioRatio

(a) 0% N(a) 0% N22 UNCD, (b) 5% NUNCD, (b) 5% N22 UNCD, (c) 10% NUNCD, (c) 10% N22 UNCD, (d) 20% NUNCD, (d) 20% N22UNCD. Grain size increase from 4 to 16 nm; grain boundary width UNCD. Grain size increase from 4 to 16 nm; grain boundary width increases from 0.5 to 2.2 nm. Nincreases from 0.5 to 2.2 nm. N22 is incorporated preferentially at the is incorporated preferentially at the grain boundaries.grain boundaries.

Grain + Grain boundary morphologyGrain + Grain boundary morphology

J. J. BirrellBirrell et al., App. Phys. Let., Vol. 81, pp. 2235et al., App. Phys. Let., Vol. 81, pp. 2235--2237, 2002.2237, 2002.


100 nm

Super GrainsSuper Grains


Scanning Probe Microscopy Characterization of Scanning Probe Microscopy Characterization of UNCDUNCD

Effect of Substrate: Si vs. W/Si(Top Surface)

(a) (b)

(a) Topside of an undoped UNCD film on a Si substrate with roughness of 20 nm. (b) Topside of an undoped UNCD film on a W/Si substrate with roughness of 14 nm.

M. Hersam’s group


Scanning Probe Microscopy Characterization of Scanning Probe Microscopy Characterization of UNCD (UNCD (con’tcon’t))

Effect of Substrate: Si vs. W/Si(Bottom Surface)

(a) Backside of an undoped UNCD film on a Si substrate with roughness of 3 nm. (b) Backside of an undoped UNCD film on a W/Si substrate with roughness of 1 nm.

(a) (b)


Contact Mode AFM MeasurementsContact Mode AFM Measurements

Initial cAFM Data(Undoped vs. N2 Doped UNCD)

0

2E-11

4E-11

6E-11

8E-11

1E-10

1.2E-10

0 2 4 6 8 10 12

Voltage (V)

Curr

ent (

A)

UpsweepDownsweep

0.E+00

1.E-09

2.E-09

3.E-09

4.E-09

5.E-09

6.E-09

7.E-09

8.E-09

9.E-09

0 2 4 6 8 10 12

Voltage (V)Cu

rren

t (A)

UpsweepDownsweep

Undoped: R ~ 50 GΩ 10% N-Doped: R ~ 0.3 GΩ

cAFM I-V spectroscopy taken with a Pt coated tip

M. Hersam’s group


Mechanical TestingMechanical Testing•• ModulusModulus•• StrengthStrength•• Fracture ToughnessFracture Toughness


Wafer Level MicroWafer Level Micro--scale Tension Testscale Tension Test

Membrane Deflection Experiment (MDE)-Use Nanoindenter to stretch membrane-Obtain load-deflection response and stress-strain curve, extract E, σr and σf

-Fracture Toughness, KIC

H.D. Espinosa et al., J. Mech. Phys. Sol., Vol. 51, pp. 47-67, 2003

Gauge AreaLine-load Tip Membrane

InterferometricObjective


UNCD MDE SpecimensUNCD MDE Specimens

20 µm

Non-uniformities due to wafer seeding process

200 µm

4” wafer


Fabrication StepsFabrication Steps

Si substrate <100>(a)

(b)

(c)

(d)

Si3N4

UNCD

Al film

Etch Si (wet)

Etch UNCD (RIE)

Etch Si3N4 (RIE)

Fabrication steps on <100> Si wafers:(a) Deposition of UNCD film followed by Al film deposition(b) Wet etching of Al to define the pattern of UNCD(c) Dry etching of Si3N4 followed by wet etching of Si(d) Dry etching of UNCD (O2 plasma), removing the Al film


Stress CalculationsStress Calculations

PV

Wafer

MirauMicroscopeObjective

PMPMθ

LM

∆

)sin(2)()(θ

σm

V

AtPt =

Am = membrane cross-sectional area

PV(t) = load at time t

σ(τ) = Stress at time t

Cauchy Stress

Combined AFM/Nanoindenter with Integrated Mirau Microscope-Interferometer

H.D. Espinosa et al. J. Mech. Phys. Sol., Vol. 51, No. 1, pp. 47-67, 2003


Strain CalculationsStrain Calculations

λ = wavelength of interferometer light.

δ = distance between fringes

ε(t) = Strain at time t

Strain

1)2/(

)(22

−+

=δλδ

ε t

θ1

Fringes(c)

3λ/4 λ/2 λ/4λ/2

δ

Fringes

Bottom surface of membrane


StessStess--Strain CurvesStrain Curves

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045

Strain

Stress (MPa)

Undoped

5% Nitrogen

10% Nitrogen

20% Nitrogen

σσf1 f1 = 4.17 = 4.17 GPaGPa

σσf2 f2 = 2.71 = 2.71 GPaGPa

σσf3 f3 = 2.45 = 2.45 GPaGPa

σσf4 f4 = 2.35 = 2.35 GPaGPa

The stress at 63% failure probability

23502350244624462713271341724172σσ00 ((MPaMPa))

833833--865865854854--880880878878--921921940940--970970E (E (GPaGPa))

3030303030303030No. of testsNo. of tests

20%20%10%10%5%5%0%0%NN22 percentagepercentage

DopedDopedUndopedUndopedSampleSample


200200400800Side Wall Area (µm2)

12008200840032800Total Surface Area (µm2)

5002000400016000Volume (µm3)

10.511Thickness (µm)

5202040Width (µm)

100200200400Length (µm)

DCBASamples

undopedundoped B. Peng et al., submitted to J. Appl. Phys., 2004

−−=

mWeibullf V

VP0

max

0

exp1σσ

NiPf

2/1exp −=

−−=

mWeibullf A

AP0

max

0

exp1σσ

Size Effect Size Effect –– Applicability of Applicability of Weibull Weibull TheoryTheory


WeibullWeibull TwoTwo--parameter Modelparameter Model

or

−−= e

m

Vf VP )(exp1

0

max

σσ

−−= e

m

Af AP )(exp1

0

max

σσ

6.5

7.5

8.5

9.5

10.5

11.5

0.5 1.5 2.5 3.5

Scaling Parameters

Cha

ract

eris

tic S

tren

gths

( σ0V

or σ

0V)

Size ASize BSize CSize D

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

2500 3500 4500 5500

Failure Stress (MPa)

Prob

abili

ty o

f Fai

lure

Sample C

Volume

Total Surface Area

Side wall Area

Volume Surface Sidewall

Estimate the two Weibull parameters, σ0v/σ0A and m, by nonlinear regression

Volume was found to be the control factor m = 11.6, σ0V = 8581 MPa×µm3/m


FractographicFractographic Analysis (Analysis (undopedundoped))

2 µm

Grain nucleation layer

Top surface

Cluster of grains

Intergrannular FracturePolysilicon

W.N. Sharpe et al., J. MEMS, Vol. 12, 2003


FractographicFractographic Analysis (doped)Analysis (doped)

DefectsDefects

5% N5% N2 2 dopeddoped



Size Effect Size Effect –– Applicability of Applicability of Weibull Weibull TheoryTheoryundopedundoped

20% N20% N2 2 dopeddoped10% N10% N2 2 dopeddoped


m = 11.6, σ0V = 8581 MPa×µm3/m

m = 9.3, σ0V = 5719 MPa×µm3/mm = 9.7, σ0V = 5786 MPa×µm3/m

m = 10.7, σ0V = 5933 MPa×µm3/m


WeibullWeibull Studies of Studies of SiCSiC (CWRU) and (CWRU) and tata--C (SNL)C (SNL)

S iC

0

0 .10 .2

0 .3

0 .40 .5

0 .6

0 .7

0 .80 .9

1

6 0 0 16 0 0 2 6 0 0 3 6 0 0F a ilure S t re s s ( M P a)

Size A

Size B

t a - C

00.10.20.30.40.50.60.70.80.9

1

3000 4000 5000 6000 7000F a ilure S tre s s (M P a )

Size ASize B

Size A: 20µm wide, 200µm long, and 1 µm thick

Size B: 5mm wide, 100mm long, and 0.5 mm thick

SiC is deposited in a hot-wall, rf-induction-heated, (LPCVD) furnace. ta-C (hydrogen-free tetrahedral amorphous carbon) is deposited by pulsed laser deposition (PLD).


Determining the Scaling ParametersDetermining the Scaling ParametersSiC

6

8

10

12

14

0.5 1.5 2.5 3.5

Cha

ract

eris

tic S

treng

ths

(*)

Size ASize BPooled value


DLC

7

8

9

10

11

12

0.5 1.5 2.5 3.5

Cha

ract

eris

tic S

treng

ths

(*) Size ASize BPooled value


Mirror region

Ta-C

Mirror region

Si-C


Fracture Strength Fracture Strength –– WeibullWeibull VerificationVerification

SiC

-5

-4

-3

-2

-1

0

1

2

2000 4000 6000 8000 10000Fracture Strength (MPa)

LN(L

N(1

/(1-P

f))

Pooled

DLC

-5

-4

-3

-2

-1

0

1

2

5000 7000 9000Fracture Strength (MPa)

LN(L

N(1

/(1-P

f))

Pooled

ta-C

−−= e

m

Af AP )(exp1

0

max

σσ

m = 5.4

σ0A = 6780 MPaxµm2/m

m = 12

σ0A = 8020 MPaxµm2/m

Sidewalls are the scaling factors for SiC and ta-C


Summary of the Mechanical PropertiesSummary of the Mechanical Propertiesand and Weibull Weibull ParametersParameters

SidewallVolumeSidewallScaling parameter

8020±401 [(MPa×(µm)2/m]

8560±428 [(MPa×(µm)3/m]

6780±339 [(MPa×(µm)2/m]σ0V or σ0A

12.0±0.6011.6±0.585.4±0.27Weibull modulus

5260±4594680±5405080±5553990 ±4282680 ±5562090 ±519Fracture Strength at 63% prob. (MPa)

795±34801±22955±21960±25435±15422±18Young’s modulus (GPa)

501±12896±33515±211050±77527±29855±53Thickness (nm)

303030303030No. of tests

Size BSize ASize BSize ASize BSize A

ta-CUNCDSiCMaterial


Thin Film Fracture ToughnessThin Film Fracture Toughnessand Theoretical Strength and Theoretical Strength

EstimateEstimate


Fracture Toughness Fracture Toughness –– Sharp CrackSharp Crack

)(WafaK fIC πσ=

σ σ

a

W

4.10.7018.18.2

4.50.7118.26.6

4.70.7818.05.8

4.40.9518.23.9

4.11.3518.12.1

KIC

(MPa m1/2)

σfexp

(GPa)

W

(µm)

a

(µm)

H.D. Espinosa and B. Peng, J. MEMS, 2004

...)(72.21)(55.10)(23.012.1)( 32

Wa

Wa

Wa

Waf −+−=


Stress Intensity Stress Intensity –– Blunt NotchesBlunt Notches

σ σa

a

W

1 2

10 µm

6.9----Average

6.91.534.915

7.01.734.114

6.61.674.013

6.41.683.712

6.91.883.511

6.51.783.510

6.82.082.79

6.62.142.48

6.62.192.37

6.72.282.26

7.02.412.15

6.42.272.04

6.52.461.73

7.12.691.72

6.93.231.01

K’IC(MPa m1/2)

σfexp

(GPa)a

(µm)SampleNumber

)(WafaK fIC πσ=

32 )(44.15)(78.4)(429.012.1)(Wa

Wa

Wa

Waf +−+=

Crack tipFracture surface

1 µm

H.D. Espinosa and B. Peng, Submitted to J. MEMS, 2004


Blunt Notch CorrectionBlunt Notch Correction

ρnotch

x

y

a

ρ

( )

+=

xxKx I

y 21

2ρ

πσ ICIC K

xK

+=

21/ ρ

( )∫ ≥0

0dd

uy dxx σσ

ICIC Kd

K0

/

21 ρ+= 2

2

02

u

ICKdσπ

=

Novozhilov’s brittle fracture criterion, 1969

Stress field for blunt crack (Creager, 1967) Drory et al. 1995

σu is a strength characteristic value for the material without defects (the ideal strength of the material at the characteristic size of d0 )

N. Pugno, B. Peng, and H.D. Espinosa, Int. J. Sol. Struc., 2004


Blunt Notch CorrectionBlunt Notch Correction

a

ρ

a

ρ

a

ρ

35.79.22.8516.22.2490

37.07.93.5516.21.2230

33.58.63.5216.31.4220

39.27.82.5016.12.1170

35.67.32.2516.12.2140

37.37.02.0416.22.4100

d0

[nm]

Κ’IC[MPa m1/2]

σf(exp)[GPa]

W

[µm]

a

[µm]

ρ

[nm]

dd00 is estimated to be ~37 nm and is estimated to be ~37 nm and σσuu = 18 = 18 GPaGPa

N. Pugno, B. Peng, and H.D. Espinosa, Int. J. Sol. Struc., 2004


Quantum Mechanics Quantum Mechanics SimulationsSimulations

G.C. Schatz, T. G.C. Schatz, T. Belytschko Belytschko and Z. Cheng (UMC)and Z. Cheng (UMC)


Method Used for Determining Modulus and Method Used for Determining Modulus and Fracture PropertiesFracture Properties

MSINDO: A semi-empirical molecular orbital program. Electron repulsion is included explicitly but most integrals are modeled. Two- and three-dimensional periodic boundary conditions are available in this code.

UNCD models: Some include grain boundaries (GBs).

no GB one GB two GBs


EnergyEnergy--Strain Curve for Strain Curve for UndopedUndoped Diamond with 2Diamond with 2--D D Boundary Condition and One Grain BoundaryBoundary Condition and One Grain Boundary


Diamond with 2Diamond with 2--D Boundary Conditions, and One D Boundary Conditions, and One Grain Boundary Grain Boundary DopedDoped with Two Nitrogen Atomswith Two Nitrogen Atoms


0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

0

1

2

3

4

Diamond with 2Diamond with 2--D Boundary Conditions, and One D Boundary Conditions, and One Grain Boundary Grain Boundary DopedDoped with Two Nitrogen Atomswith Two Nitrogen Atoms

Applying strain in different ways can result in qualitatively different fracture paths.


EnergyEnergy--Strain Curve for Strain Curve for UndopedUndoped Diamond with 3Diamond with 3--D D Boundary Conditions and Two Grain BoundariesBoundary Conditions and Two Grain Boundaries


EnergyEnergy--Strain Curve for Strain Curve for UndopedUndoped Diamond with 3Diamond with 3--D D Boundary Conditions and No Grain BoundariesBoundary Conditions and No Grain Boundaries


RemarksRemarks

Two- and three-dimensional boundary condition calculations predict UNCD mechanical properties that are the same, semi-quantitatively.

Doping with two two nitrogen atoms is not sufficient to substantially alter the mechanical properties of UNCD.

Issues related to the existence of multiple fracture pathsmultiple fracture paths complicate the analysis.

Unstrained Strain = 0.1 Broken


AFM Chips with Wear AFM Chips with Wear Resistant TipsResistant Tips

N. N. MoldovanMoldovan, B. , B. PengPeng, H.D. Espinosa and M. , H.D. Espinosa and M. Hersam Hersam


Contact Mode AFM Contact Mode AFM PotentiometryPotentiometryExperimental Setup:

A

Onset offailure

0.8V 1V

Evolution of nanowire failure:

M. C. Hersam, A. C. F. Hoole, S. J. O'Shea, and M. E. Welland, Appl. Phys. Lett., 72, 915 (1998).

(Breakdown current density = 3.75×1012 A/m2)Wire width = 60 nm

B

Failurepoint

0.9V 1.8V

Conductive tip with small Rc (kΩ range).

Low Rc must be sustained after extensive scanning.


UNCD UNCD PotentiometryPotentiometry ChipChip

Au h~100-500 µm

UNCDdoped to be conductive

Phase 1 : A single probe chip

Conductive AFM techniques can be improved with tips Conductive AFM techniques can be improved with tips coated with conformal and highly conductive UNCD films.coated with conformal and highly conductive UNCD films.

h~3-7 µm


Preliminary ResultsPreliminary Results


Molecular Writing with Diamond Tips

MHA solution in ethanol with concentration at 1 mM• scan rate: 6 Hz• vertical deflection: -2 V (left), -1 (right)• contact time: 50, 25, and 13 sec• gains: (Int, Prop, LookAhead) = (4, 4, 0)• patterning on a Au substrate prepared on 7/2/04 (left), 7/8 (right)• image processing: low pass & detrend (left)

Science 283, 661 (1999)


Massively Parallel UNCD Massively Parallel UNCD PotentiometryPotentiometryPhase 2 : Integrated multiple probes

Contact pads

UNCD

PYREX 7740

Si (B++ doped)eventually oxidized

•Independent electrodes for potentiometry

•Independent actuation (thermal?)

•Multiplexing


Thermal Actuation / MultiplexingThermal Actuation / Multiplexing

Crossing-over of lines multiple metallization (2+1)

Insulator layer increase in stiffness

Parasitic capacitances

Address Input Lines

col 1 col 2 col NColum n Select

row 1

row 2

row 3

row M

Data Input Buffers and

Control


NEMS NEMS NanoresonatorsNanoresonatorsAnomalous Q FactorAnomalous Q FactorBreak down of Break down of WeibullWeibull

B.B. PengPeng, N. , N. MoldovanMoldovan, H.D. Espinosa, H.D. Espinosa


UNCD UNCD NanoresonatorsNanoresonators-- Anomalous Q FactorAnomalous Q Factor

ραϖ

12

2 EtL

=

StoredEnergy DissipatedEnergy

=QE-beam lithography pattern


Concluding RemarksConcluding Remarks• Mechanical properties of UNCD were investigated by this

work. Young’s modulus of 960 GPa, fracture strength of 5 GPa for undoped UNCD, fracture toughness of 4.5 MPam1/2, and ideal strength of 18.6 GPa associated to a characteristic length of 37 nm.

• We showed that Weibull statistics is capable of predicting fracture strengths of MEMS materials with different sizes.

• Molecular dynamics model was used to simulate the mechanical properties from atomic species and imperfections.

• AFM cantilevers with sharp tips made of UNCD have been microfabricated and molecular writing demonstrated.


http://clifton.mech.northwestern.edu/~espinosa/

B. Peng, Northwestern UniversityN. Moldovan, Northwestern UniversityO. Auciello, ANLJ. Carlisle, ANLX. Xiao, ANLM. Hersam, Northwestern UniversityG.C. Schatz, Northwestern UniversityT. Belytschko, Northwestern UniversityB. Prorok, Aurburn University

Acknowledgments:Acknowledgments:

NSF-Nano Science Interdisciplinary Research Teams (NIRT), Award Number CMS-00304472 National Science Foundation, GOALI Award No. CMS-0120866/001

Ivan Petrov, UIUCD. Mancini, ANLJ. Mahon, UIUCM. Marshall, UIUCR.S. Divan, ANLZ. Chen, UMCC.A. Zorman, CWRUT.A. Friedmann, SNLN. Pugno, Politecnico di Torino, Italy

Science and Technology of Ultrananocrystalline Diamond Films for Multifunctional … ·...

Documents

Transcript of Science and Technology of Ultrananocrystalline Diamond Films for Multifunctional … ·...