Atomic layer deposition: a true and enabling …...Atomic layer deposition: an enabling technology Department of Applied Physics – Erwin Kessels Knoops et al., Handbook of Crystal

Atomic layer deposition: a true and enabling nanotechnology

Erwin Kessels

[email protected]/pmp

Outline

Department of Applied Physics – Erwin Kessels

1. Introduction

2. Atomic layer deposition (ALD)

3. ALD materials & Applications of ALD

4. Atomic layer etching (ALE)

5. Summary

Evolution of personal devices

Department of Applied Physics – Erwin Kessels Twitter - HistoryInPix

Scaling in semiconductor industry

Department of Applied Physics – Erwin Kessels Kessels – Inaugural lecture (2012)

2020s

Integrated photonics

Artificial intelligence

Quantum computing

…

FinFET transistors


Intel 22 nm

www.intel.com

Fin

Source Drain

Gate

High-koxide

Precise and conformal deposition of high-k metal gate (HKMG) stack

FinFET transistors


Intel 10 nm

www.intel.comIEEE-IEDM (2017)

52 nm

34 nm

7 nm

Intel 22 nmPrecise and conformal deposition of high-k metal gate (HKMG) stack

Evolution of data storage


5 MB IBM hard disk - 1956

Twitter - HistoryInPix

3D NAND memory


Precise and conformal deposition of oxide layers and charge trap layer

Samsung V-NAND 48L

www.techinsights.comJ. Jang et al., Dig. Symp. VLSI Tech. 192 (2009)

3D NAND memory

Department of Applied Physics – Erwin Kessels www.techinsights.com

Precise and conformal deposition of oxide layers and charge trap layer

Samsung V-NAND 48L Samsung V-NAND 32L

Atomic layer deposition: an enabling technology

Department of Applied Physics – Erwin Kessels Knoops et al., Handbook of Crystal Growth Vol III, 2nd ed. (2015)

Precise and conformal deposition of ultrathin films with Ångstrom-level thickness control at (fairly) low temperatures

atomic-layer by atomic-layer

Outline


1. Introduction


• What is ALD?

• Mechanism of ALD: the prototypical Al2O3 case

• ALD process development, ALD history, ALD tools



5. Summary

What is ALD?


ALD is a CVD-like technique in which film growth takes places by repeating cycles Each cycle consists of 2 (or more) “half-reactions” separated by purge/pump steps

The “half-reactions” are self-limiting leading to well-defined amount of added material

Knoops et al., Handbook of Crystal Growth Vol III, 2nd ed. (2015)

What is ALD?


0 50 100 150 200 2500

10

20

301. Al2O3

2. SiO2

3. Ta2O5

4. ZnO2

5. TiO2

Thick

ness

(nm

)

ALD Cycles

Films grown by repeating cycles until desired thickness is reachedIn every cycle 1 atomic layer is added with a perfect repeatability

Parameter for “growth rate” is

“growth-per-cycle” (GPC)

Mostly expressed in thickness-per-cycle

Typically 0.01 – 0.15 nm/cycle

Potts et al., J. Electrochem. Soc. 157, P66 ( 2010)

Key merits of ALD


Key merits of ALD: 1) Ångström-level growth control2) Unparalleled uniformity3) Excellent conformality4) Low substrate temperature (< 500 ⁰C)

Knoops et al., Handbook of Crystal Growth Vol III, 2nd ed. (2015)

Uniformity and conformality


ALD CVDPVD

PECVD

Materials prepared by ALD

Department of Applied Physics – Erwin Kessels Inspired from Puurunen, J. Appl. Phys. 97, 121301 (2005)www.AtomicLimits.com

The ALD database – www.AtomicLimits.com

Department of Applied Physics – Erwin Kessels https://doi.org/10.6100/alddatabase

The ALD database – www.AtomicLimits.com

Department of Applied Physics – Erwin Kessels https://doi.org/10.6100/alddatabase

Self-limiting behavior for ALD Al2O3


0 20 40 60 80 1000.00

0.05

0.10

0.15

0.20

Gro

wth

per C

ycle

(nm

/cyc

le)

Dose time (ms)0 1 2 3 4 5

Purge time (s)0 1 2 3 4 5

(b)

Plasma time (s)

(a)

Subsaturation

0 1 2 3

CVD

Purge time (s)

0 20 40 60 80 1000.00

0.05

0.10

0.15

0.20

Gro

wth

per C

ycle

(nm

/cyc

le)

Dose time (ms)0 1 2 3 4 5

Purge time (s)

CVD

0 20 40 60 80

Subsaturation CVD

H2O dose (ms)0 1 2 3

Purge time (s)

Ther

mal

ALD

(H

2O)

Plas

ma

ALD

(O2

plas

ma)

Dingemans and Kessels, J. Vac. Sci. Technol. A 30, 040802 (2012).

ALD of Al2O3 ― Mass spectrometry


Gas phase reaction products

0 25 50 75 10010-11

10-10

10-9

10-8

H2O

Mas

s sp

ectro

met

ry s

igna

l (A)

Time (s)

CH4

Al(

CH

3)3

Al(

CH

3)3

Al(

CH

3)3

Al(

CH

3)3

H2O

H2O

H2O

H2O

0 25 50 75 10010-11

10-10

10-9

10-8

H2O

Mas

s sp

ectro

met

ry s

igna

l (A)

Time (s)

CH4

0 25 50 75 10010-11

10-10

10-9

10-8

H2O

Mas

s sp

ectro

met

ry s

igna

l (A)

Time (s)

CH4

Al(

CH

3)3

Al(

CH

3)3

Al(

CH

3)3

Al(

CH

3)3

H2O

H2O

H2O

H2O

Al(CH3)3 dosing: CH4

H2O dosing: CH4

Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017)

ALD of Al2O3 ― In situ infrared spectroscopy

Department of Applied Physics – Erwin Kessels Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017)

4000 3500 3000 2500 2000 1500 1000

4x10-5

Infra

red

abso

rban

ceWavenumber (cm-1)

OH stretching

CHxstretching

CHxdeformation

2940 cm-1 1207 cm-1

Al(CH3)3chemisorption

H2Oexposure

Monitoring surface groups

Al(CH3)3 dosing: -OH replaced by -CH3

H2O dosing: -CH3 replaced by -OH

ALD of Al2O3 ― Ellipsometry & RBS

Department of Applied Physics – Erwin Kessels Potts et al., J. Electrochem. Soc., 157, P66 (2010)Vandalon and Kessels, J. Vac. Sci. Technol. A 35, 05C313 (2017)

0 100 200 300 4000123456

0.0

0.1

0.2

(b)

Substrate temperature (oC)

Plasma ALD Thermal ALD

# Al

ato

ms

per c

ycle

(

1014

cm

-2)

Gro

wth

rate

(nm

/cyc

le)

(a)

O2 plasma

(Ideal) ALD temperature window


Plasma-enhanced ALD


Merits of plasma ALD:• Improved material properties• Deposition at reduced temperatures• Increased choice of precursors/materials• Good control of film composition• Increase growth rate• More versatility in general• ….

Profijt et al., J. Vac. Sci. Technol. A 29, 050801 (2011)Knoops et al., J. Vac. Sci. Technol. A 37, 030902 (2019)

Challenges of plasma ALD:

• Limited conformality• Plasma-induced damage• …

PlasmasO2H2N2

NH3Etc.

10 steps to successfully develop an ALD process

Department of Applied Physics – Erwin Kessels See blog on ALD process development on www.AtomicLimits.com

History of ALD

Department of Applied Physics – Erwin Kessels To appear on www.AtomicLimits.comSee for ALD history also: Puurunen, Chem. Vap. Deposition 20, 332 (2014)


Atomic layer deposition (ALD) equipment


Research & Development High volume manufacturing

Outline


1. Introduction



• Oxides, nitrides, metals, fluorides, sulfides

• From nanoscale applications to large-area applications


5. Summary

ALD of metal oxides


0 50 100 150 200 2500

10

20

301. Al2O3

2. SiO2

3. Ta2O5

4. ZnO2

5. TiO2

Thick

ness

(nm

)

ALD Cycles

Potts et al., J. Electrochem. Soc. 157, P66 ( 2010)

1. Al(CH3)3

2. SiH2{N(C2H5)}2

3. Ta{N(CH3)2}5

4. Zn(CH2CH3)2

5. Ti(Cp*)(OCH3)3

H3C AlCH3

CH3

(H3C)2N TaN(CH3)2

N(CH3)2

N(CH3)2

N(CH3)2

TiH3CO OCH3

OCH3

H3CCH3

CH3

H3C CH3

SiH H

N(C2H5)2

N(C2H5)2

H3C

H2C

Zn

H2C

CH3

+H2O, O3 or O2 plasma

FinFET transistors with high-k metal gate (HKMG)


Intel 10 nm

www.intel.comIEEE-IEDM (2017)

52 nm

34 nm

7 nm

Intel 22 nmhigh-k gate dielectric = HfO2 - metal gate = TiN

FinFETs in Apple A11 and A12 chips

Department of Applied Physics – Erwin Kessels www.msscorps.com

TEM image

EDS elemental mapping

Topview of SRAM of A11 and A12

A11 – Iphone 8 - TSMC 10 nm processA12 – Iphone Xs - TSMC 7 nm process

The biggest ALD market - patterning

Department of Applied Physics – Erwin Kessels Beynet et al., Proc. of SPIE 7520, 75201J-1 (2009)See blog about patterning on www.AtomicLimits.com

Line-width

Pitch ALD of SiO2(50 ºC) Double pitch Line-width =

thickness ALD film1 Litho step!

Self-aligned double patterning (SADP) – since 22 nm node

SADP – SAQP – SAOP *** 193i or EUV litho


Self-aligned quadruple patterning (SAQP) – since 10 nm node for finFETs

193 nm immersion with self-aligned octuple patterning (SAOP) or EUV with SADP

Arstechnica.com & IBM research Decoster et al., Proc. of SPIE 10589, 105890E-1 (2018)

SAOP (with 3 ALD steps)

outperformsEUV-based litho

in terms of roughness

ALD market development

Department of Applied Physics – Erwin Kessels Knoops et al., J. Vac. Sci. Technol. A 37, 030902 (2019)

2004

2006

2008

2010

2012

2014

2016

2018

2020

0

200

400

600

800

1000

1200

1400

Forecasts

2017

2014

2013

2008

ALD

Mar

ket S

ize ($

M)

Year

Actual

(a)

ALD market size has grown tremendously over last decade, even beating predictions!

Excellent conformality of ALD


Encapsulation of defects by Al2O3/TiO2 “nanolaminate”

Courtesy of Jian Jim Wang (NanoNuvo Corporation, USA)

Excellent conformality of ALD


Al2O3

c-Si

SiO2

Black Si Si nanowires

Van de Loo et al., Appl. Phys. Lett. 110, 263106 (2017).Collaboration with Erik Bakkers et al. (TU/e)

ALD for nanowire devices


Surface passivation of semiconducting nanowires (for LEDs, nanolasers, solar cells)

Black et al., Nano Lett. 17, 6287 (2017).

ALD for MEMS-type devices


Mechanically tunable photonic crystal with two membranes suffering from stiction

Petruzzell et al., Optics Express 28, 3882 (2018)

15 nm of Al2O3 prevents stiction of membranes when actuated

Advanced ALD cycles (beyond AB-type cycles)

Department of Applied Physics – Erwin Kessels Knoops et al., Handbook of Crystal Growth Vol III, 2nd ed. (2015).

ALD of doped materials: e.g., Al-doped ZnO


TEM image of ZnO:Al using TMA (3 supercycles)

Increasing the carrier density by decreasingthe cycle ratio (more supercycles)

Wu et al., J. Appl. Phys. 114, 024308 (2013)Garcia et al., J. Mater. Chem. C 3, 3095 (2015)

Many more doped materials proven, for example TCOs: ZnO:X (X = Al, B, Ga), In2O3:X (X=H, Sn), TiO2:X (X=Nb)

ALD of metals: initial growth and nanoparticles


0 100 200 300 400 500 60002468

101214

Th

ickne

ss (n

m)

Number of cycles

100 nm

ALD of Pt from MeCpPtMe3 and O2 on Al2O3 substrate (300 ⁰C)

Mackus et al., Chem. Mater. 25, 1905 (2013)

Nucleation delay on Al2O3

PtH3C CH3

CH3

CH3

ALD of nanoparticles


100 cycles 200 cycles 300 cycles



50 nm

Weber et al., J. Phys. Chem. C 118, 8702 (2014)

ALD of Pd from Pd(hfac)2 and H2 plasma and O2 plasma (ABC-type cycle, 100 ⁰C)

0 1 2 3 4 5 6 7 80

10

20

30

40

50

Num

ber o

f NPs

Diameter (nm)

50 cycles 100 cycles 150 cycles 200 cycles 300 cycles

Nanoparticle size distribution(monodisperse, 1 – 5 nm diam.)

ALD of core-shell nanoparticles


20 nmIMG1(frame1) 20 nm

Pd L 20 nm Pt M 20 nm

2 nm

Pt

PdAl2O3

HAADF-STEM imaging

EDS mapping

Weber et al., Chem. Mater. 24, 2973 (2012)

ALD for catalysis


substrate

ALDSupport

Layer

activesupport

ALDCatalyst

small, monodispersednanoparticles

ALDStabilization

Layer

stabilized catalyst

Lu et al., Science 335, 1205 (2012)

Catalytic oxidative dehydrogenation of ethane C2H6 + O2 C2H4 + CO + CO2 + H2O + H2

Nanoparticles with ALD overcoat do not sinter and don’t suffer from no heavy

coke formation

ALD of 2D metal sulfides


450 ⁰C

ALD of MoS2 from (NtBu)2(NMe2)2Mo and H2S plasma at < 450 ⁰C

Sharma et al., Nanoscale 10, 8615 (2018)

Initially formation of horizontal layers and subsequent formation of vertical fins

ALD of 2D metal sulfides


450 ⁰C

ALD of MoS2 from (NtBu)2(NMe2)2Mo and H2S plasma at < 450 ⁰C

Initially formation of horizontal layers and subsequent formation of vertical fins For 10 cycles (~10 Å nominal) monolayer signature (Raman & photoluminescence)

350 375 400 425 450

∆ = 21 cm-1∆ = 24.1 cm-1

Ram

an In

tens

ity (a

.u.)

Raman Shift (cm-1)

50 cycles 30 cycles 20 cycles 10 cycles

as-deposited@450°C

∆ = 25.2 cm-1∆ = 25.6 cm-1

Sharma et al., Nanoscale 10, 8615 (2018)

ALD for silicon solar cells


Al2O3 nanolayers (~5 nm) lead to excellent passivation of silicon surfaces

Chemical&

field-effect passivation

Dingemans et al., J. Vac. Sci. Technol. A 30, 040802 (2012)International Technology Roadmap for Photovoltaic, 9th ed. – September 2018

PERC solar cell

High-volume ALD in photovoltaics


x

t

China Photovoltaic Industry Development Roadmap - 2018 ed. (January 2019)

Spatial ALD for photovoltaics


Wafer move from one side to the other (up to 6000 wafers/hr)ALD process at atmospheric pressure

Levitech B.V. - www.levitech.nlNote: spatial ALD also provided by SolayTec B.V. – www.solaytec.com

Other potential large application areas


• Silicon & perovskite solar cells• Flexible solar cells…• Tandem cells…

• Displays• From TFEL displays (mid 80’s)• To flexible (smartphone) displays…

• Li-ion batteries• ALD on particles…• Solid-state batteries…

• Catalysis• Model studies…• Microreactors…?

Roll-to-roll (R2R) ALD

Fluidized-bed (FB) ALD

Outline


1. Introduction




• What is ALE?

• Anistropic and isotropic ALE

5. Summary

Atomic layer deposition & etching (ALD & ALE)


Deposit or etch layer-by-layer

Atomic layer deposition & etching (ALD & ALE)

Department of Applied Physics – Erwin Kessels Faraz et al., J. Solid State Sci. Technol. 4, N5023 (2015).

ALE with ion bombardment (anisotropic etching)


• Example, Si etching with Cl2 gas and Ar plasma (Ar+)

• Precise ion energy control to be within ALE window

0 50 100 150 200 250Io

n en

ergy

dis

tribu

tion

func

tion

Ion energy, Ei (eV)

Atomic layer deposition & etching (ALD & ALEt)

Department of Applied Physics – Erwin Kessels Faraz et al., J. Solid State Sci. Technol. 4, N5023 (2015).

History of ALE

Department of Applied Physics – Erwin Kessels To appear on www.AtomicLimits.comSee for ALE history also: Kanarik et al., J. Vac. Sci. Technol. A 33, 020802 (2015)

FinFET transistors


Intel 22 nm

www.intel.com

Fin

Source Drain

Gate

High-koxide

Precise and conformal deposition of high-k metal gate (HKMG) stack

Gate-all-around FETs – sub-5 nm node


IBM sub-5 nm

Nanosheet

SourceDrain

Gate

High-koxide

IBM, Global Foundries, Samsung – IBM News Room, June 5, 2017See also blog about atomic-scale processing on www.AtomicLimits.com

Gate-all-around FETs – sub-5 nm node

Department of Applied Physics – Erwin Kessels IBM, Global Foundries, Samsung – IBM News Room, June 5, 2017Loubet et al., Symp. on VLSI Technology Digest of Technical Papers (2017)

Si/SiGe stack Fin etching(anistropic)

SiGe etching(istropic)IBM sub-5 nm

Summary


• Atomic layer deposition (ALD)

• ALD as true & enabling nanotechnology

• ALE an “etch-counter” part for ALD – still in its infancy but rapidly emerging!

o Oxides, nitrides, metals, sulfides, fluorides, ….

o Thin films, nanoparticles, 2D materials, …

ALD Academy (www.ALDacademy.com)

Prof. Erwin KesselsDept. of Applied Physics

Eindhoven University of Technology

Prof. Gregory ParsonsDept. of Chemical and Biomolecular Engineering

North Carolina State University

Mission: educate students and professionals on the principles, applications and future advancements of ALD and related atomic-scale processes.

January 14/15, 2020 - Eindhoven

ALD Academy on Atomic Layer Etching & DepositionNew event:

Register at www.ALDacademy.com


Acknowledgments

PMP group – January 15, 2019

Documents

Atomic layer deposition: a true and enabling …...Atomic layer deposition: an enabling technology Department of Applied Physics – Erwin Kessels Knoops et al., Handbook of Crystal