Chemical selectivity and nucleation during ALD of Ru with the RuO4-precursor

Matthias M. Minjauw,a Hannes Rijckaert,b Isabel Van Driessche,b Christophe

Detavernier,a Jolien Dendoovena

a Ghent University, Conformal Coating of Nanostructures (CoCooN)b Ghent University, Sol-gel Centre for Research on Inorganic Powders and Thin films Synthesis (SCRIPTS)

Introduction – Applications of Ru thin films

Bulk resistivity 7 μΩ.cm Work function > 4.7 eV Conductive oxide RuO₂ 40 μΩ.cm Electromigration Adhesion to Cu

2

Sub-10 nm interconnect Liner for Cu

Bernasconi et al. J. Electrochem. Soc. 2019, 166, D3219.

Introduction – ALD of Ru - Literature

3

Type Precursor Reactant T – window GPC (nm/cyc) Growth delayMetallocenes and RuCp₂ O₂ 275°C-400°C 0.05 < 300 cycles Aaltonen 2003

derivatives Ru(EtCp)₂ O₂ 270°C 0.15 < 200 cycles Kwon 2004

(EtCP)Ru(DMPD) O₂ 230°C – 280°C 0.04 < 50 cycles Kim 2007, 2010

(EtCp)Ru(Py) O₂ 275°C – 350°C 0.09 < 100 cycles Kukli 2011

Ru(DMPD)₂ O₂ 185°C – 215°C 0.01 < 100 cycles Methaapanon 2012

Tris-β-diketonates Ru(thd)3 O₂ 350°C 0.04 < 1000 cycles Aaltonen 2004

Zero-valent IMBCHDRu O₂ 220°C 0.09 < 30 cycles Eom 2009

Cyprus O₂ 250°C – 300°C 0.05 < 50 cycles Gregorczyk 2011

EBECHDRu O₂ 140°C – 350°C 0.04 < 10 cycles Hong 2012

EBCHDRu O₂ 140°C – 350°C 0.10 < 50 cycles Yeo 2013

IMBHDRu O₂ 230°C – 350°C 0.08 < 10 cycles Jung 2014

EBBDRu O₂ 225°C 0.06 < 100 cycles Yeo 2015

Ru(DMBD)(CO)3 O₂ 290°C – 320°C 0.07 < 100 cycles Austin 2017

100°C

150°C

50°C

• RuO4 / H2 – process

• ToRuSTM (Air Liquide)

• 20% H2 in Ar

Introduction – ALD of Ru - Literature

4

ALDRu

Ru

H2(1) not

saturating

(2) non-

reactive

T

M. M. Minjauw et al. J. Mater. Chem. C, 2015, 3, 132.

(1)(2)

UGent mobile ALD reactor for in situ X-ray studies

5

Lab configuration

In situ ellipsometry

Synchrotron configuration

In situ XRF, GISAXS and XAS

X-ray Fluorescence (XRF)

6

XRF provides info

on atomic composition

1 2 3 4 5 6 7 8 9 10

0

100

200

300

400

500

Fe

KCr

K

Cu

K

Fe

K

Cr

KTi

K

Ti

K

Ar

K

Ar

K

Mo L

XR

F in

ten

sity

Energy (keV)

Si K

In situ XRF for chemical selectivity – example for HfO2 ALD

7Devloo-Casier et al. Appl. Phys. Lett. 2011, 98, 231905.

GPC = 1.2 Å/cycle

In situ XRF for chemical selectivity – example for HfO2 ALD

8Devloo-Casier et al. Appl. Phys. Lett. 2011, 98, 231905.

In situ XRF for chemical selectivity – example for HfO2 ALD

9Devloo-Casier et al. Appl. Phys. Lett. 2011, 98, 231905.

In situ XRF for chemical selectivity – example for HfO2 ALD

10Devloo-Casier et al. Appl. Phys. Lett. 2011, 98, 231905.

Sub-monolayer sensitivity makes XRF ideal tool for monitoring initial ALD growth

A. Area-selective Ru ALD

11

Ru ALD on blanket substrates

12

/ H2

0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70

Ru

LX

RF

in

ten

sit

y(1

0³

co

un

ts)

# cycles

Thermal ALD, Si-H

Thermal ALD, SiO₂

Ru ALD on Si/SiO2 patterned substrate

• Planar SEM-EDX

13Si SiO2

50 μm

/ H2

Ru ALD on Si/SiO2 patterned substrate

• Cross-section (S)TEM

14

4.5 nm

/ H2

SiSi

SiO2

Proposed mechanism during half reaction (1)

15

Steady Ru growth

Ru Ru

SiSiO2

SiSi

H H H

SiSiO2

Nucleation regime

Turbo-

molecular

pump

In vacuo XPS setup @ Ghent University

16

XPS

ALD

13.56 MHz ICP

plasma source

Transfer mechanism

Sample

Transfer time

< 1 min

hν

e-

10-7 mbar

10-10 mbar

SiSiO2

SiSi

H H H

SiSiO2

In vacuo XPS during first Ru half cycle

17

Single pulse

Summary

18

Ru growth on SiH

Nucleation delay on SiO2SiSiO2

SiSi

H H H

SiSiO2

SiSiO2

SiSiO2

R R R ?

B. Nucleation enhancement

19

Hypothesis – nucleation enhancement

20

SiSiO2

SiSiSiO2

Al

H3C CH3

Combustion of methyl groups by RuO4

Hypothesis

In vacuo XPS during first Ru half-cycle

Single pulse10s

5.10-3 mbar

Ru ALD on blanket films

• In situ spectroscopic ellipsometry

22

4.5 nm

/ H2+ n

Ru film properties

Substrate # cycles Thickness (nm) Roughness (nm) ρ (µΩ.cm) Oxygen (at. %)

Si-H 75 18.5 0.3 36 4

SiO2 200 17.3 2.2 35 5

SiO2 + TMA 75 13.3 0.4 37 4

23

All other impurities below detection limit of XPS

Conclusions

24

SiSiO2SiO2

/ H2+ n

SiSiO2SiO2

SiHigh quality RuSiO2 SiO2

Area-selective Ru ALD

“Ru on everything”

/ H2 n

High quality Ru

Minjauw et al. Chem. Mater. 2019, 31, 5, 1491-1499.

Acknowledgements

• Co-authors:

Hannes Rijckaert, Isabel Van Driessche, Christophe Detavernier, Jolien Dendooven

• Promotors:

Christophe Detavernier, Jolien Dendooven

• Colleagues at CoCooN

• Funding:

25

Questions?

Most likely approach can be extended

beyond Si/SiO2 and to different priming

Minjauw et al. Chem. Mater. 2019, 31, 5, 1491-1499.

Additional slides

27

Ru film resistivity as a function of thickness

28

[1] Kukli et al. J. Electrochem. Soc. 2010, 157, D35.

[2] Kukli et al. J. Electrochem. Soc. 2011, 158, D158.

[3] Kukli et al. Thin Solid Films 2012, 520, 2756.

Steady ALD Ru growth

29

H2 (1)(2)

O1s Scan 20eV

260

280

300

320

340

CP

S

544 540 536 532 528Binding Energy (eV)

Ru3d Scan 20eV

x 102

5

15

25

35

CP

S

292 288 284 280 276Binding Energy (eV)

Ru3d Scan 20eV

x 102

5

10

15

20

CP

S

292 288 284 280 276Binding Energy (eV)

O1s Scan 20eV

x 101

242832364044

CP

S

544 540 536 532 528Binding Energy (eV)

31% 69%

92%8%

Ru

Ru

O1s Ru3d

PEALD

H2

ALD100°C

150°C

50°C

• RuO4 / H2* – process

• ToRuSTM (Air Liquide)

• 20% H2 in Ar, 300 W

Introduction – PEALD of Ru - Literature

30

Ru

Ru

(1) not

saturating

T

M. M. Minjauw et al. J. Mater. Chem. C, 2015, 3, 4848.

(1)(2)H2*

H2H2*

O1s Scan 20eV

240

260

280

300

CP

S544 540 536 532 528

Binding Energy (eV)

Ru3d Scan 20eV

x 102

5

15

25

35

CP

S

292 288 284 280 276Binding Energy (eV)

Steady ALD Ru growth

31

(1)(2)Ru3d Scan 20eV

x 102

5

10

15

20

CP

S292 288 284 280 276

Binding Energy (eV)

O1s Scan 20eV

x 101

242832364044

CP

S

544 540 536 532 528Binding Energy (eV)

31% 69%

96%4%

Ru

Ru

O1s Ru3d

Hypothesis

Single pulse10s

5.10-3 mbar

Ru3d Scan

x 102

6

10

14C

PS

296 292 288 284 280 276 272

Bindi ng Energy (eV)

O1s Scan

x 103

2

6

10

CP

S

544 540 536 532 528 524

Bindi ng Energy (eV)

Al2p Scan

x 101

16

20

24

28

CP

S

84 80 76 72 68 64

Bindi ng Energy (eV)

Si2p Scan

x 102

5

15

25

CP

S

108 104 100 96 92

Bindi ng Energy (eV)

• In situ spectroscopic ellipsometry

SiSiO2

SiSiO2

Ru ALD on blanket substrates

33

/ H2

~ 15nm

In situ XRF @ Soleil synchrotron

34

0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70

Inte

gra

ted

Ru

L in

ten

sit

y (10³

co

un

ts)

# cycles

Thermal ALD, Si-H

Thermal ALD, SiO₂

PEALD, SiO₂

Resistivity

35

Si

SiO2

Al

H3C CH3

Si

H H H

Si

SiO2Si

SiO2

Al

H3C CH3

Hypothesis

36

O2-plasma

ISE thickness fit

37

Model: Drude-Lorentz harmonic oscillator