the pe-ald of ta based metals/nitrides: the growth ......stability • various phase: solid-solution...

Thomas J. Watson Research Center

The PEThe PE--ALD of Ta Based Metals/Nitrides: The Growth, Materials ALD of Ta Based Metals/Nitrides: The Growth, Materials Properties, and Applications to Future Device FabricationsProperties, and Applications to Future Device Fabrications

Hyungjun Kim and Steve M. Rossnagel

Thomas J. Watson Research CenterIBM Research Division


12/12/02

TFUG/PEUGNorthern California Chapter

AVS


Atomic Layer DepositionAtomic Layer Deposition

♦ ALD (Atomic Layer Deposition): Self-limiting film growth method by alternate exposure of chemical species in layer-by-layer manner.• Good conformality• Easily controlled thickness at the atomic scale• Atomic level composition control• Large area uniformity• Low impurity at low growth temperature

♦ For sub-100 nm node with Cu interconnect,• Ultra thin/highly conformal diffusion barrier.

ALD is a promising technique.


Tungsten plug for via hole

Cu diffusion barrier/adhesion promoterCu seed layer

Metal gate electrode Diffusion barrier

Potential Applications of ALD Metals/Nitrides in Nanoscale DevicPotential Applications of ALD Metals/Nitrides in Nanoscale Deviceses


Ta and TaN Thin FilmsTa and TaN Thin Films

♦ Ta• Good resistivity

α phase (bcc): 15-60 µΩ cm(β phase (tetragonal): 170-210 µΩ cm)

• High thermal stability (Tm = 2669 °C)• No intermetallic compound with Cu• Cu has very low lattice diffusivity in Ta.

♦ TaN• High chemical, mechanical, and thermal

stability• Various phase: solid-solution α phase Ta,

hexagonal Ta2N, hexagonal TaN, cubic TaN, hexagonal Ta5N6, tetragonal Ta4N5, orthorhombic Ta3N5

Binary Alloy Phase diagrams, ASM International, 1990


Ta and TaN layer for Cu interconnectTa and TaN layer for Cu interconnect

♦ TaN/Ta bilayer liner

• Good adhesion: resisting delamination during process or thermal processing, high EM resistance

• Liner/ILD and Cu/liner adhesion have conflicting dependencies on N content for TaNx

– Ta adhesion on SiO2 (low k) is poor: TaN on SiO2 (low k) is require.– Cu adhesion on TaN is poor: Cu on Ta is required.

TaN/Ta bilayer is the only viable option so far.– TiN/Ta causes corrosion for some CMP process– alpha Ta formation on TaN: low in-plane resistivity

Ref) D. Edelstein et al, Proc. 2001 IITC, 9 (2001).

Both Ta and TaN have good DB property. Why bilayer liner?

Currently PVD is used, but if we want to implement ALD liner process…Need ALD process for both Ta and TaN liners!


Ta/TaN ALDTa/TaN ALD : Precursors: Precursors

♦ Ta metal precursor• Halides: TaCl5, TaBr5, TaI5, all solid source• MO source: N is contained

♦ Ta ALD: Ta halides + reducing agents• Molecular H2: require above 700 °C

♦ TaN ALD• Halides + NH3 : high resistivity Ta3N5• MO sources: high C content

TaN

NN

NN CH3

CH3

CH3

CH3

CH3CH3

CH3

CH3

CH3

CH3Ta N

N

N

N

C

CH3

CH3

CH3

CH3CH3

CH3CH3

CH3 CH3

PDMAT TBTDET


Strategy for Ta based metals/nitrides ALDStrategy for Ta based metals/nitrides ALD

TaCl5

+ hydrogenplasma

Ta

+ hydrogen/nitrogenplasma

TaNx

+ hydrogen/nitrogenplasma

+SiH4

TaSiyNx

+ SiH4

TaSi2

OR

+ nitrogen plasma


Experimental Setup for PEExperimental Setup for PE--ALDALD

Quartz tubeRF coil

200 mm wafer

H and/or N 2 2

Leak valve

TaCl solid source5Ceramic heater

Turbo pump

Leak valve


Growth ProcedureGrowth Procedure

TaCl adsorption 5

extraction

tTaCl5

TaCl on5 TaCl off5 H2 on

TaCl pump out

5

plasma on

tp

plasma off

pump out

Gate valve off

TaCl purgeby H

5

2

1 Cycle

TaCl5 (a) + 5H (g) → Ta(a) + 5HCl (g)↑


PEPE--ALD Ta: SelfALD Ta: Self--limited Adsorptionlimited Adsorption

♦ Saturation condition: tH > 4 s, tTaCl5 > 1 s♦ Saturated growth rate: 5.3x1013 /cm2 (0.08 Å/cycle)

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.50

1

2

3

4

5

6

7Ts = 250 °CtH= 5 s

PE-ALD Ta

Num

ber o

f Ta

atom

s/C

ycle

(101

3 /cm

2 )

tTaCl5 (s)


PEPE--ALD Ta: Plasma Exposure TimeALD Ta: Plasma Exposure Time

0 2 4 6 80

1

2

3

4

5

6

7

8Ts = 250 °CtTaCl5

= 2 sPE-ALD Ta

Num

ber o

f Ta

atom

s/C

ycle

(101

3 /cm

2 )

tH (s)


PEPE--ALD Ta: MicrostructureALD Ta: Microstructure

30 35 40 45 50

x1000

On TaN On SiO2

(b) ALD Ta

Inte

nsity

(a.u

.)2θ (°)

β Ta (002)

α Ta (110)

On TaN On SiO2

(a) PVD Ta

ALD Ta

PVD Ta

♦ Resistivity: ρ = 150-180 µΩcm → close to β-Ta phase♦ RBS: Cl concentration = 0.5-2 at% at Ts < 300 °C


PEPE--ALD TaNALD TaNxx : Mixture of N and H: Mixture of N and H

10-3 10-2 10-1 1

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

tTaCl5= 2 s

tp = 5 sTs = 300 °C

Number of Ta atoms/Cycle

PE-ALD TaN

Num

ber o

f Ta

atom

s/C

ycle

(101

4 /cm

2 )

PN2/PH2

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

N/Ta

N/T

a ra

tio

♦ Growth rate (for N/Ta = 1): 1.2x1014 /cm2 (0.24 Å/cycle)♦ Easy control of N content


PEPE--ALD TaN: Growth TemperatureALD TaN: Growth Temperature

100 200 300 4000

5

10

15

20

25

30

tTaCl5= 2 s

tp = 5 sPN2

/PH2 = 0.025

Cl H

PE-ALD TaN

Cl,

H c

onte

nt (a

t %)

Ts (°C)0

200

400

600

ρ

ρ (µ

Ωcm

)


PEPE--ALD TaN: XRDALD TaN: XRD

25 30 35 40 45 50 55 60 65

cubic TaN

cubic TaNTa3N5

x2

(e) PN2/PH2

= 0.65

Inte

nsity

(a.u

.)

2θ (°)

(d) PN2/PH2

= 0.25

(c) PN2/PH2

= 0.025

(b) PN2/PH2

= 0.004

ALD TaN/SiO2Ts = 300 °C

Ta2N

(a) PN2/PH2

= 0.001

25 30 35 40 45 50 55 60 65

(c) 100 °C

Inte

nsity

(a.u

.)

2θ (°)

(b) 200 °C

PN2/PH2

= 0.025ALD TaN/SiO2(a) 300 °C

111 200 220


PEPE--ALD TaN: TEMALD TaN: TEM

SiO2

TaN


PEPE--ALD TaN: ResistivityALD TaN: Resistivity

♦ ρ 300 − 400 µΩ cm for N/Ta = 1

0.2 0.4 0.6 0.8 1.0 1.2 1.4

103

104

tTaCl5= 2 s

tp = 5 sTs = 300 °CPE-ALD TaN

ρ (µ

Ωcm

)

N/Ta ratio


PEPE--ALD TaN: MEIS (Medium Energy Ion Spectroscopy)ALD TaN: MEIS (Medium Energy Ion Spectroscopy)

80 85 90 95 100

102

103

104

Ta

SiON

30 A TaNPE-ALD TaN/Si

Ion

yiel

d (C

ount

s)

Energy (KeV)

TaNOx


Comparison with Previously Reported ALD TaN Comparison with Previously Reported ALD TaN

1) M. Ritala, P. Kalsi, D. Riihelä, K. Kukli, M. Leskelä, and J. Jokinen, Chem. Mater. 11, 1712 (1999).2) M. Juppo, M. Ritala, and M. Leskela, J. Electrochem. Soc. 147, 337 (2000).3) P, Alén, M. Juppo, M. Ritala, M. Leskelä, T. Sajavaara, and J. Keinonen, J. Mater. Res. 17, 107 (2002).4) P, Alén, M. Juppo, M. Ritala, T. Sajavaara, J. Keinonen, and M. Leskelä, J. Electrochem. Soc. 148, G566 (2001).5) J.-S. Park, H.-S. Park, and S.-W. Kang, J. Electrochem. Soc. 149, C28 (2002).

3)0.1 – 0.35-Cl > 2C: 1 - 20> 1300TaNTaCl5a)+tBuNH2

(allylNH2)+(NH3)

2)0.13 – 0.31-Cl < 0.5Too highAmorphousTaCl5+DMHy

5)0.87.9C: 15-35400 - 2000TaNTBTDET+HPlasma

This study0.249.8Cl < 0.5350TaNTaCl5 +H+N

1.1

0.66 – 0.94

0.15 – 0.2

0.24

Growth rate(A/cycle)

5)3.6C: 15> 105AmorphousTBTDET+NH3

4)-Al: 30-32Br: 4> 6600Ta(Al)N(C)TaCl5 +NH3+TMA

1)-Cl < 4> 900TaNTaCl5a) + NH3+Zn

1)-Cl < 1> 105Ta3N5TaCl5a) + NH3

Thermal

Ref.Density (g/cm3)Impurityb)

(at %)Resistivity

(µΩcm)PhasePrecursors

a) Similar results for TaBr5b) Cl content at 400 °C


PEPE--ALD TaNALD TaNxx : With nitrogen plasma: With nitrogen plasma

♦ N/Ta = 1.3, ρ = 105 µΩ cm: high resistivity Ta3N5 phase ♦ Low Cl (< 1%)

30 35 40 45 50

Orthorhombic

PE-ALD Ta3N5

132

113

023

Inte

nsity

(a. u

.)

2θ (°)


PEPE--ALD ALD TaSiNTaSiN

♦ Use SiH4 as Si source

♦ a: SiH4 →TaCl5 → H+N plasma• High resistivity, polycrystalline• Ta (15%) N(45%) Si(40 %)

♦ b: TaCl5 → SiH4 → H+N plasma• Low resistivity, amorphous film• Ta (20%) N(25%) Si(55 %)

30 40 50

TaCl5 → SiH4 → H+N plasma

TaN (111)

Inte

nsity

(a. u

.)

2θ (°)

TaN (200)

SiH4 → TaCl5 → H+N plasma ALD TaSiN


Thermal ALD TaSiThermal ALD TaSi22

♦ Growth without plasma :TaCl5 + SiH4♦ RBS: Ta/Si = 0.5, Cl < 1%, no H

10 20 30 40 50 60 70 80 90 1000

Si223

312311

220

203

211112

200

Si

003

111

110102

101

100

HexagonalALD TaSi2

Inte

nsity

(a.u

.)

2θ (°)


ConformalityConformality

Ta TaN


200 cycles

Ta TaN

RMS: 0.206 nm

MorphologyMorphology

1600 cycles

RMS: 0.123 nm

RMS: 0.106 nm

RMS: 0.153 nm


Thermal Stability: PEThermal Stability: PE--ALD TaALD Ta

200 300 400 500 600 700 800 900 10000

10

20

30

40

50

60 SiALD Ta/Si

Si c

onte

nt (a

t.%)

Annealing Temp (°C)

0

2

4

6

8

10

12

14 H Cl

Cl,

H c

onte

nt (a

t. %

)

♦ 30 minutes annealing in He.♦ PVD Ta reacts with Si at 700 °C.(Ref)

Ref) K. Holloway, P.M. Fryer, C. Cabral, Jr. J.M.E. Harper, P.J. Bailey, KH. Kellerher, JAP 71, 5433 (1992)


Thermal Stability: PEThermal Stability: PE--ALD TaNALD TaN

♦ Surface O reduced by annealing. (3Å thick after 900 °C)

80 85 90 95 100

102

103

104

Ta

SiON

As-dep 700 °C, 60 secs 800 °C, 60 secs 900 °C, 60 secs 1000 °C, 30 secs

30 A TaNPE-ALD TaN/Si

Ion

Yie

ld (C

ount

s)

Energy (KeV)


Cu Diffusion Barrier Property Test StructuresCu Diffusion Barrier Property Test Structures

PVD Cu (200 nm)

Poly Si

Si

ALD Ta or TaN

RMS: 23.51 nm

RMS: 2.126 nm

Before annealing

After annealing

Cu/Ta/Poly Si

♦ Roughness, resistivity, phase change


In Situ Characterization During Rapid Thermal AnnealingIn Situ Characterization During Rapid Thermal Annealing

♦ At National Synchrotron Light Source, Brookhaven National Laboratory.♦ 3 °C/s in He, from 100 to 1000 °C.♦ Similar system without XRD for routine measurements

NSLS

Beamline X20C

Lock-in #1

Lock-in #2HeNeLaser

X-Ray Diffraction - Phase FormationOptical Scattering - Surface RoughnessResistance - Electrical Characterization

Measurement and Control Electronics

LinearX-ray Detector

AnnealingChamber

FocusingMirror

MultilayerMonochromator

Sample

BeamlineControl

AnalysisWorkstation

ExperimentalControl


200 300 400 500 6000

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Res

ista

nce

Temperature (°C)

0

0.5

1.0

Nor

mal

ized

Opt

ical

Inte

nsity

52

50

48

46

2θ (d

eg)

PEPE--ALD Ta: Diffusion Barrier Failure TemperatureALD Ta: Diffusion Barrier Failure Temperature

660 680 700 720 740 760 780 8000

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Res

ista

nce

Temperature (°C)

0

0.5

1.0 Light Scattering 0.5 µm Light Scattering 5 µm

Nor

mal

ized

Opt

ical

Inte

nsity

56545250484644

2θ (d

eg)

Cu/ALD Ta (7 nm)/Poly-Si

Cu(111)Cu Silicide

Cu(200)

Cu silicide formation: 773 °CCu silicide formation: 260 °C

Cu/Poly-Si

Cu(111) Cu Silicide


ALD Ta (2.8 nm)

ALD Ta (14 nm)

PVD Ta (12 nm)

Cu(111)Cu Silicide

Cu(200)

Increase in failure temperature

PEPE--ALD Ta: Comparison with PVD TaALD Ta: Comparison with PVD Ta



PEPE--ALD TaN: ALD TaN: Diffusion Barrier Failure TemperatureDiffusion Barrier Failure Temperature

550 600 650 700 750 8000

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Res

ista

nce

Temperature (°C)

0

0.5

1.0

Light Scattering 0.5 µm Light Scattering 5 µm

N

orm

aliz

ed O

ptic

al In

tens

ity56545250484644

2θ (d

eg)

Cu 111

Cu 200

ALD TaN (2.5 nm, N/Ta = 1)

Cu silicide formation: 620 °C

Cu Silicide


PEPE--ALD Ta and TaN: ALD Ta and TaN: Diffusion Barrier Failure TemperatureDiffusion Barrier Failure Temperature

0 5 10 15 20 25550

600

650

700

750

800

850

ALD Ta PVD Ta ALD TaN PVD TaN

PVD Cu(200 nm)/Ta or TaN/poly-Si

Failu

re T

empe

ratu

re (°

C)

Film thickness (nm)


PEPE--ALD Ta/TaN Bilayer Cu Diffusion BarrierALD Ta/TaN Bilayer Cu Diffusion Barrier

500 600 700 800 900

Ligh

t sca

tter.

(5 µ

m)

Temperature (°C)

Ligh

t sca

tter.

(0.5

µm

)

PE-ALD Ta, 10 Å PE-ALD TaN, 25 Å PE-ALD Ta 10 Å/TaN 25 Å

She

et re

sist

ance

♦ Bilayer deposition by switching off nitrogen flow


Metal Gate for CMOSMetal Gate for CMOS

♦ Problems with poly-Si gate• Gate depletion at inversion: increase in teq• High gate resistance• Reaction with high k • Boron Penetration

♦ Requirements • Workfunction : 0.2eV from Ec(n-FET) or Ev(p-FET)

– nFET : Ta, Ti, TaN, TaSiN…– pFET: Ru, Pt…

• Thermal & chemical stability with gate oxide• Low resistivity

Metal gate


Deposition Technique of Metal GateDeposition Technique of Metal Gate

♦ Little damage to gate oxide♦ Low temperature deposition with low impurity to avoid reaction with gate

oxide♦ Conformality at nanoscale structure

a. Conventional Device Fabrication and oxide CMP

b. Remove Sacrificial Gate Stackc. Deposit New Gate Stack and CMP patter gate

SpacerPoly

Silicide

Oxideoxidespacer

PolySilicide

Spacer

Silicide

Oxide

spacer

Silicideoxide

Spacer

Silicide

Gate dielectric

OxideMetalMetal

Gate Dielectric

spacer

Silicideoxide

Ref) A. Chaterjee et al, IEDM Tech. Digest, 821 (1997)

ALD of metal gate

replacement gate processRef)


PEPE--ALD TaN as Metal GateALD TaN as Metal Gate

♦ Capacitor structure: PE-ALD TaN/100 Å SiO2♦ Work function: 4.4 ± 0.1 eV♦ Little change in tox up to 1000 °C RTA

-2 -1 0 1 20

200

400

Quasi static High frequency

PE-ALD TaN/100 Å SiO2C

apac

itanc

e (n

F/cm

2 )

Voltage (V)


Nanoscale Device FabricationNanoscale Device Fabrication

♦ Self-assembling diblock copolymer process• Alternative to photoresists for nanoscale dimensions

1.surface pretreatment

2.spin diblock copolymer and bake

3. liquid develop

PS PMMA

remove PMMAsilicon

polystyrene

K.W. Guarini, C. T. Black, Y. Zhang, H. Kim, and I. V. Babich, 2002 3-Beams Conference, Anaheim, CA


PEPE--ALD TaN ElectrodeALD TaN Electrode

1159%10:1

570%5:1

98%1:1

9%0.5:1

capacitance increase

aspect ratio

20 nm pores, 42 nm spacing 4 nm oxide thickness

PE-ALD TaN

♦Pattern transfer to Si substrate: enhanced surface area ♦Fabrication of capacitor with high storage capacity


ConclusionsConclusions

♦ Successful growth of Ta based metals/nitrides at low Ts by ALD using chloride precursor and plasma.

♦ Ta and TaN PE-ALD processes as a function of key growth parameters

♦ Analysis of PE-ALD Ta and TaN thin film properties

♦ Applications of PE-ALD Ta based metals/nitrides in modern semiconductor devices processing


CollaboratorsCollaborators

♦ Andrew Kellock♦ Cyril Cabral, Jr. ♦ Christian Lavoie♦ Christophe Detavernier♦ Dae-Gyu Park♦ James Harper♦ Kathryn Guarini♦ Matt Copel♦ Michael Lane♦ Mike Gribelyuk♦ Roy Carruthers♦ Vijay Narayanan


Evaluation for Cu linersEvaluation for Cu liners(ref)(ref)

Ref) D. Edelstein et al, Proc. 2001 IITC, 9 (2001).

the pe-ald of ta based metals/nitrides: the growth ......stability • various phase: solid-solution...

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