Invited talk at 98th CSC: Surface chemistry of ALD: mechanisms and conformality

VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD

Surface chemistry of ALD:

mechanisms and

conformality

98th Canadian Chemistry Conference Surface Chemistry for Thin Film Deposition Session

Riikka L. Puurunen

VTT Technical Reseach Centre of Finland, Ltd.

2 R. L. Puurunen, Can. Chem. Conf., Ottawa, June 14, 2014

Outline

Introduction to ALD

1. Me3Al/H2O Al2O3:

Surface chemistry of the ALD model system

2. Thin film conformality analysis

3. History of ALD


ALD: based on repeated self-terminating gas-solid

reactions (chemisorption)

ALD cycleReactant A

Reactant B

By-product

Substratebefore ALD

Step 2 /4purge

Step 4 /4purge

Step 1 /4 Reactant A

Step 3 /4Reactant BALD cycle

Reactant A

Reactant B

By-product

Substratebefore ALD

Step 2 /4purge

Step 4 /4purge

Step 1 /4 Reactant A

Step 3 /4Reactant B

ALD cycles

Mass

* Type of non-

continuous CVD

process


Self-terminating gas-solid reactions in ALD:

saturating, irreversible

desorption non-saturation unsaturation

amount adsorbed saturates

amount adsorbed stays

NO:

pulse purge

Source: Puurunen (review), J. Appl. Phys. 97 (2005) 121301.


ALD research status overview

Current version, ”2nd edition” (2010): Miikkulainen, Leskelä, Ritala, Puurunen (review), J. Appl. Phys. 113 (2013) 021301.

”1st edition” (2004): Puurunen (review), J. Appl. Phys. 97 (2005) 121301.

5


Various types reactants (precursors) used

Source and further details: Puurunen, J. Appl. Phys. 97

(2005) 121301

Update: Miikkulainen, Leskelä, Ritala, Puurunen, J. Appl.

Phys. 113, (2013) 021301

H2O NH3

H2S

O3 N2 H2

”Normal” ALD

Energy-enhanced ALD (PEALD)

O2

Metal Non-metal

Inorganic compounds

Organometallic compounds

Metal-organic compounds


1 Surface chemistry

8 R. L. Puurunen, Can. Chem. Conf., Ottawa, June 14, 2014 From: Puurunen, EuroCVD 2007 (in SlideShare)

http://www.slideshare.net/RiikkaPuurunen/euro-cvd-162007puurunenv10


Me3Al/H2O – has evolved to The Model System

Puurunen, 2005, J. Appl. Phys.

Me3Al/H2O surface chemistry critically reviewed & discussed

George, 2010, Chem. Rev.

” The ALD of Al2O3 has developed as a model ALD system.

An earlier extensive review by Puurunen … [Puurunen2005]”

Knapas & Ritala, 2013, Crit. Rev. Solid State Mater. Sci.

”The AlMe3 (TMA) – H2O process … the most studied ALD

system, and has also been adopted as a model system for

ALD [George2010].”

Weckman & Laasonen, 2015, Phys. Chem. Chem. Phys.

” … the TMA/H2O system is considered as a model process for

ALD [George2010, Puurunen2005]”

859

930

(16)

Cited

WoS

12.6.2015

(0)


Puurunen, 2005, J. Appl. Phys.

Me3Al/H2O surface chemistry critically reviewed & discussed

George, 2010: Chem. Rev.

” The ALD of Al2O3 has developed as a model ALD system.

An earlier extensive review by Puurunen …

[Puurunen2005]”

Knapas & Ritala, 2013, Crit. Rev. Solid State Mater. Sci.

”The AlMe3 (TMA) – H2O process … the most studied ALD

system, and has also been adopted as a model system for

ALD [George2010].”

Weckman & Laasonen, 2015, Phys. Chem. Chem. Phys.

” … the TMA/H2O system is considered as a model process

for ALD [George2010, Puurunen2005]”

Me3Al/H2O – The Model System

Let us treat the Me3Al/H2O process

with the critical eye

that the model system deserves


Some fundamental questions related to ALD

How does the GPC vary with temperature?

What is the ALD window of a given process?

What defines the Growth Per Cycle (GPC)?

What is the limiting factor that causes saturation?

Which surface reaction mechanisms take place?

How fast are they?

Postulate: different works

explain the variation in GPC

in significantly different ways

12 R. L. Puurunen, Can. Chem. Conf., Ottawa, June 14, 2014 From: Puurunen, EuroCVD 2007 (in SlideShare)



[Puurunen2005]

Fitting reference: Puurunen,

Appl. Surf. Sci. 245 (2005) 6-10

Quantitative explanation of GPC

vs temperature via loss of [OH]

and ~constant [Me]

From: Puurunen, EuroCVD 2007 (in SlideShare)



[Puurunen2005] Data behind the fitted equation

+ more data for [Me]

Puurunen et al., J. Phys. Chem. B 104 (2000) 6599

Puurunen et al., Phys. Chem. Chem. Phys., 3 (2001) 1093


[Me]



[Puurunen2005]

Field: Authors Record Count

KESSELS WMM 7

ADOMAITIS RA 4

POTTS SE 4

PUURUNEN RL 4

DINGEMANS G 2

DWIVEDI V 2

HARLIN A 2

KENTTA E 2

KIM J 2

KREUTZER MT 2

ROOZEBOOM F 2

SALO E 2

TRAVIS CD 2

VAHA-NISSI M 2

VAN HEMMEN JL 2

VAN OMMEN JR 2

WALLACE RM 2

Cited, 12.6.2015,

WoS: 36 times




[George2010]

”

”


Data behind the conclusion: annealing experiment

300C 100C

[Me]

[George2010]

Room-temperature exposure!

Qualitative description of GPC

vs temperature via loss of [OH]

and loss of [Me]


[Knapas2013]

• No explanation for

temperature trends of GPC

• n/z value considered as

mechanism, weak trend

with temperature (if any)

• discussion on H2O dose

”

”


Data behind, [Me]: QCM and QMS studies ref. 108

Ref 108

Water not saturated (?)

Was Me3Al saturated?

[Me]

[Knapas2013]


Conclusion, The Model System

Source Puurunen, 2005 George, 2010 Knapas & Ritala,

2013

Explaination of

less-than-

monolayer GPC &

temp. trend

Quantitative Qualitative

-

Description of

GPC change with

temperature

Decreases with

* decreasing [OH],

* [Me] ~constant

Decreases with

* decreasing [OH],

* decreasing [Me]

(* n/z about

constant at 1.5)

Background data,

Change of

surface [Me] vs

temperature

[Me] [Me] [Me]


Conclusion

Source Puurunen, 2005 George, 2010 Knapas & Ritala,

2013

Explaination of

less-than-

monolayer GPC &

temp. trend

Quantitative Qualitative

-

Description of

GPC change with

temperature

Decreases with

* decreasing [OH],

* [Me] ~constant

Decreases with

* decreasing [OH],

* decreasing [Me]

* n/z about

constant at 1.5

Change of surface

[Me] vs

temperature in

”background data”

[Me] [Me] [Me]

• Significant differences, which have remained

unnoticed so far?

• Me3Al/H2O is model system

scientific discussion & agreement on the

basic trends needed

• New research activity welcome!


2 Conformality


Thin film conformality: one of the

fundamental advantages of ALD

Ritala et al.,

CVD 5 (1999) 7

Photo: Kalevala-koru Suntola; Lakomaa et al.

• #1 volume ALD application based on reactor sales

• Production: TiN-ZAZ-TiN, ZyALDTM (story, FinALD40)

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4

Ge

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len

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ta

lk, A

VS

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Catalysis Silver

protection DRAM

Suntola,

MRS Boston 1994

Microelectronics


… but how deep exactly does the coating go?

… and how uniform is it?

Gordon et al.,

Chem. Vap.

Deposition

9 (2003) 73.

“small dose” “high dose”

Dendooven et al.,

J. Electrochem. Soc. 156

(2009) P63

”a”:

ALD Ru, AR 50/1 ALD TiN, AR 50/1

Detavernier, Tutorial, AVS-ALD conference, Kyoto, June 2014


VTT: microscopic Si LHAR test structures for

ALD growth & conformality evaluation

25 mm

20 m

m l

(side view)

l

g

Aspect ratios

Lateral length l (µm)

Gap (nm) 5000 1000 500 200 50 20

200 25000 5000 2500 1000 250 100

500 10000 2000 1000 400 100 40

1000 5000 1000 500 200 50 20opening 100 80 60 40 20 10

opening

”PillarHall”

Gao et al., J. Vac. Sci. Technol. A 33 (2015) 010601.


0

20

40

60

80

100

120

0 20 40 60 80 100 120

Thic

kne

ss (

nm

)

Distance from port opening

Al2O3 ALD in PillarHall chips, 500 nm gap VTT Micronova

• Full coverage up to

60 µm / AR ~120

• Thereafter linear decrease

Distance (µm) / AR

40 80 120 160 200 240 0

Me3Al/H2O, PICOSUN R-150

300°C, 0.1 – 4 - 0.1 - 4 s sequence



TiO2 ALD in PillarHall chips, different gaps VTT Micronova

• Slow initial decrease up to

~AR 80, steep decrease

from AR ~120 on

• Gap size affects the

results?

TiO2 at 110°C, ~100 nm



O2

O3 + H2

O2 long purge

* Automatic line scan: ~1 µm spot; GMRFILM Max AR 10 000:1

Top-view SEM +

EDS line scan

Iridium ALD in PillarHall chip, 500 nm gap University of Helsinki – Mattinen, Ritala

ASM F120 reactor

250C

250C

185C

Ir(acac)3


Conclusion, ALD conformality analysis

PillarHall LHAR chips expose a new

parameter space for ALD modelling

Up to AR 25000:1, molecular flow

Sensitive detection of decay shapes

Strong basis for modelling

Future ideas/Discussion:

Line scan database for modelling? Interested parties for modelling?

Which parameters stored?

Round Robin test for an ALD process?

Process? Interested parties? HERALD?


3 ”All men by nature desire to know”

Tuomo Suntola Aristotle

ALD History


Virtual Project on the History of ALD (VPHA) in atmosphere of Openness, Respect and Trust

Volunteer-based effort: collect & read & summarize all early ALD

literature up to 1986

Questions especially related to Molecular Layering,

also Atomic Layer Epitaxy

Started in Summer 2013, to end summer 2016

Uses cloud services & professional social media for fluent

collaboration

Joint publications as outcomes

Condition for participation: ability to work

in atmosphere of Openness, Respect and Trust

LinkedIn group: ALD History

https://www.linkedin.com/groups/ALD-History-5072051/about









Publication Plan v3 & outcomes http://vph-ald.com/Publication%20Plan.html

1) Poster at Baltic ALD 2014 - done

2) Poster at ALD 2014, Kyoto - done

3) Presentation at ALD 2014, Kyoto - done

4) ALD history tutorial at ALD 2014, Kyoto – done

5) Essay on the early history of ALE-ALD – done

6) Website for ALD history and VPHA – done, http://vph-ald.com

7) Exhibition: 40 years of ALD in Finland - Photos, Stories (FinALD40) –

done

8) Review article/essay on the early history of ML-ALD - ongoing

9) Presentation at ALD 2016 - ongoing

10) Optional: general ALD history review article

11) Updating wikipedia

12) Closing the VPHA

Baltic ALD 2014 Helsinki

Baltic ALD 2015 Tartu

ALD Russia 2015 Moscow

http://vph-ald.com/Publication Plan.html






http://vph-ald.com/

http://vph-ald.com/

http://vph-ald.com/


ALD History outlook:

VPHA looks for more participants

There are now ~35 participants

There are now 324 papers listed for up to 1986

Each paper should be read by about three people

we have to write roughly 1000 comments altogether

We could have even 100 participants

Your participation

is most welcome &

needed! To participate, contact though

LinkedIn or email Riikka


Acknowledgements

Funding: Academy of Finland,

Finnish Centre of Excellence on Atomic Layer Deposition

ALD conformality analysis test structures & analysis:

VTT: Gao Feng, Meeri Partanen, Jaana Marles, Antti Tolkki

University of Helsinki: Miika Mattinen, Mikko Ritala

ALD history

Tuomo Suntola, Anatoly Malygin, Jonas Sundqvist

All participants of VPHA (>30)

American Vacuum Society (announcements, tutorial)

Contact:

riikka.puurunen@ vtt.fi


Thank You!

Atomikerroskasvatus

שכבות אטומיות השקעת

εναπόθεση ατομικού στρώματος

Atomlagenabscheidung

Parmanu Parat Nishepan

परमाणु परत निक्षेपण

Deposizione a Strati Atomici

原子層堆積

원자층증착

आण्विक थर लेप

Atomlagsdeponering

атомно-слоевое осаждение

Dépôt de Couches Atomiques

Dépôt Chimique en Phase Vapeur à Flux Alternés

Atomlagerdeponering

Atomik Katman Biriktirme

Oсадження атомних шарів

Aatomkihtsadestus

Depositación de Capas Atómicas

Atomic Layer Deposition Atoomlaagdepositie

原子层沉积

Deposição por Camadas Atômicas

ALD name collection in LinkedIn ALD – Atomic Layer Deposition

Mолекулярное Hаслаивание

https://www.linkedin.com/groupItem?view=&gid=1885076&type=member&item=5843740056048644097&qid=43314a3d-3593-49b9-bf7b-06bce4c5ec50&trk=groups_most_popular-0-b-ttl&goback=.gna_1885076.gmr_1885076.gmp_1885076








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