On the history and future of ALD: VPHA, conformality analysis, mechanisms

VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD
On the history and future of
ALD: VPHA, conformality
analysis, mechanisms
HERALD COST action workshop
ALD nanotechnology: advances, prospects and applications
May 22-23, 2017, Riika, Latvia
Dr. (Prof.) Riikka Puurunen,
VTT Technical Research Centre of Finland
Aalto University, School of Chemical Engineering

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Puurunen, HERALD COST action event Riika, May 22, 2017
22/05/2017 2
Thank you for the invitation! Three topics:
Virtual Project on the History of ALD
 Baltic ALD 2016, St. Petersburg, http://www.bald2016.ru/
 Slides: http://vph-ald.com/VPHApublications/VPHA-Puurunen-
etal_FINAL_2016-10-03.pdf
 Video record (partial) in Youtube: https://youtu.be/DIArUktQ8xs
ALD conformality testing with microscopic lateral structures
 On-going work at VTT, http://pillarhall.com
 Presentations to come at EuroCVD-BalticALD 2017, ALD 2017,
EuropaCat 2017, AVS64
Surface reaction mechanisms in ALD - open questions
 ALD 2016, http://ald2016.com/
 SlideShare:
https://www.slideshare.net/RiikkaPuurunen/presentation-at-ald-
2016-by-puurunen-comparison-of-al2o3-chemistry-interpretations-
final-20160723

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Presentation dedicated to the memory of
Mr. Sven Lindfors, 1945-2017
 25.11.1945 Helsinki
- 15.4.2017 Espoo
 Pioneer of ALD reactors
 Founder of Picosun
Photo: Magnus Löfving
FinALD40
exhibition
Photo from 1978

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About Prof. Riikka Puurunen
• LinkedIn: Riikka Puurunen, Twitter: @rlpuu, Aalto people
• ORCID, Hirsch index: 22 (ISI Web of Science, May 21, 2017)
• Working with ALD since 1998
• 1998, Microchemistry, Espoo, Finland (master’s thesis)
• 1999-2002 Helsinki University of Technology / Fortum Oil and Gas (doctorate)
• 2003-2004 IMEC, Leuven, Belgium
• 2004-2017 VTT, Finland
• 2017 Aalto University, Associate Prof. Catalysis Science & Technology
• http://cmet.aalto.fi/icc, Twitter: @AaltoCatalysis
• Part-time 40% at VTT Feb-Jul 2017
• Major ALD reviews: JAP 2005 (OA) JAP 2013 (OA), JVSTA 2017 (OA)
• JAP 2005 & JAP 2013 contain the ”periodic table of ALD”
• Coordinator of the Virtual Project on the History of ALD (2013-)
Photo: Erkki Pöytäniemi

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Photo by Kaupo Kukli
On the history of ALD and the VPHA
project
Riikka L. Puurunen,1 Yury Koshtyal,2 Henrik
Pedersen,3 J. Ruud van Ommen,4 Oksana
Yurkevich,5 Jonas Sundqvist6
Baltic ALD 2016, St. Petersburg, October 2016
1 Link
Full version in
* vph-ald.com
* Youtube
(SlideShare to come)

Puurunen, Teaching demonstration, 11.12.2014, Aalto UniversityPuurunen et al. Baltic ALD 2016, 2016-10-03, St. Petersburg
On the History of ALD
and the VPHA project
The 14th International Baltic Conference on Atomic Layer Deposition
Riikka L. Puurunen,1 Yury Koshtyal,2 Henrik Pedersen,3 J. Ruud van
Ommen,4 Oksana Yurkevich,5 Jonas Sundqvist6
1 VTT Technical Research Centre of Finland, Espoo, Finland
2 Ioffe Institute, St. Petersburg, Russia
3 Linköping University, Linköping, Sweden
4 Delft University of Technology, Delft, the Netherlands
5 Immanuel Kant Baltic Federal University, Kaliningrad, Russia
6 System Integration and Technology Transfer, Fraunhofer Institute for Ceramic Technologies and
Systems IKTS, Dresden, Germany

ALD cycle
Reactant A
Reactant B
By-product
Substrate
before ALD
Step 2 /4
purge
Step 4 /4
purge
Step 1 /4
Reactant A
Step 3 /4
Reactant B
Reactant A
Reactant B
By-product Adapted with permission from: Aarik et al.,
Thin Solid Films 340 (1999) 110.
* saturating, irreversible
chemisorption reactions
* repeated
Atomic Layer Deposition (ALD): a chemical
gas-phase technique for thin film growth

Source: review by Miikkulainen, Leskelä, Ritala, Puurunen, J. Appl. Phys. 113, 021301 (2013); >2000 references.
http://dx.doi.org/10.1063/1.4757907
!Drozd
Many classes of materials have been studied
by ALD: oxides, nitrides, sulfides, metals, …

• Atomic layer epitaxy (ALE), Finland, 1974 
• Molecular layering (ML), Soviet Union, 1960s 
• Молекулярное наслаивание (МН), transliterated as
molekulyarnoye naslaivanie
• Especially ML has remained poorly known and cited
Virtual Project on the History of ALD (VPHA)
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ALD discovered & developed independently
under two names
Goal of this presentation: summarize the of
key achievements in VPHA 2013-2016

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Web of Science,
Sept. 30, 2016
Knez, Nielsch, Niinistö, Adv. Mat. 2007
• “Atomic layer deposition (ALD), originally called Atomic
layer epitaxy (ALE), was developed in the 1970s by
Suntola and Antson…”
(Times cited: 426)
George, Chemical Reviews 2010
• ”The history of ALE and ALD dates back to the 1970s in
Finland.”
(Times cited: 1340)

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Puurunen, J. Appl. Phys. 2005
• “TABLE I. Some Soviet–Russian ALD
investigations.”
Ritala, M. & Leskelä, M. Nalwa, H. S.
(Ed.) Atomic Layer Deposition
Handbook of Thin Film Materials,
Academic Press, 2002, 1, 103-159
Puurunen, Doctoral thesis, Helsinki University of Technology, 2002
”Early work on Atomic Layer Deposition cited”
Malygin, Smirnov, Solid State Technology,
2002, March, p. 14

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• “According to the more commonly acknowledged
origin, ALD was developed under the name “atomic
layer epitaxy (ALE)” in Finland by Suntola and co-
workers. “
• “The less commonly acknowledged origin of ALD
dates back to … the Soviet Union … 1960s …
group of Professor Aleskovskii.”
(Times cited: 1017)
Web of Science,
Sept. 30, 2016
(Times cited: 426)
Finland.”
(Times cited: 1340)

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LinkedIn ”ALD - Atomic Layer Deposition” group
https://www.linkedin.com/groups/1885076/1885076-238399494
LinkedIn question May 6, 2013

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Atomic layer deposition (ALD) has become a technique that,
for its part, changes the world we live in. As for any significant
technology, it is interesting and important to know where the
technique came from. How was the concept developed?
What were the first ALD experiments? When, where and by
whom were they made? Why were they made?
1. First, we should generate a complete list of early ALD
publications.
2. Second, interested individuals should pick up some of the
early publications, read them, and comment on the work.
For example: was ALD made (i.e., do you recognize the
work as ALD), and if yes, which process it was; and other
noteworthy things.
3. Third, the individual should share their comments with
others, and the comments of different people should be
collected together.
Atmosphere of Openness, Respect, and Trust
VPHA opened July 25, 2013 + ALD 2013 San Diego
http://vph-ald.com/Introduction%20and%20invitation%20to%20participate.html

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ALD-history-evolving-file
Early ALD literature up to 1986
Curretly: ~300 pages
https://docs.google.com/document/d/1AlJg29dJM2if4SGzMJSSmwZskCNaAMQMO9LU6UYPios/

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Announcement made by the
conference chair Prof. Kim
http://www2.avs.org/conferences/ALD/2013/index.html

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Parsons, Elam, George, Haukka, Jeon, Kessels, Leskelä,
Poodt, Ritala, Rossnagel, JVST A 2013
• “The ALD principle… was first published under name
“molecular layering” in the early 1960s”
• “A planar thin film was not produced or evaluated.”
Published:
16.8.2013
(Times cited: 12)
• “According to the more commonly acknowledged
origin, ALD was developed under the name “atomic
layer epitaxy (ALE)” in Finland by Suntola and co-
workers. “
• “The less commonly acknowledged origin of ALD
dates back to … the Soviet Union … 1960s …
group of Professor Aleskovskii.”
(Times cited: 1017)
Web of Science,
Sept. 30, 2016
(Times cited: 426)
Finland.”
(Times cited: 1340)

14
Malygin laboratory
Publication Plan October 18, 2013 (updated Jan 13, 2014 & April 5, 2015)
Puurunen visit to St. Petersburg November 2013

”Suntola’s ALE essay” published Oct 15, 2014 & FinALD40 release
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Times cited: 7
1978 Sven Lindfors & flow reactor
Suntola Antson Lindfors
Pakkala SID conf. 1981
Microchemistry's at the MRS
1994, Boston
European SEMI Award
to Suntola 2004
10.1002/cvde.201402012/full

21
http://www.ald-mipt.ru/ald-russia.html
http://aldhistory.blogspot.fi/2015/11/ald-russia-2015-travel-report-Puurunen.html
ALD Russia Moscow + Baltic ALD Tartu Sep-Oct 2015
George
Puurunen, Malygin, Parsons
ALD Russia 2015 group photo

23
Baltic ALD 2014 Helsinki: VPHA poster + FinALD40 exhibition
ALD 2014 Kyoto: history tutorial + two posters
“ML essay” published Dec 17, 2015
10.1002/cvde.201502013/abstract

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Times cited: 0
1973 ML group
LTI by Lensovet
1977 Drozd’s reactor
1982
column
flow unit
ALE-4 Linz 1996: George,
Suntola, Drozd, Niinistö, Leskelä
2004 conf. St Petersburg
Aleskovskii, Malygin
10.1002/cvde.201502013/abstract

25
ALD 2016 Dublin:
Malygin invited talk
+ VPHA poster
Malygin
Parsons
http://vph-ald.com/UploadedPublications/Malygin-ALD2016-25July.pdf
http://vph-ald.com/VPHApublications/VPHA-poster_July2016_FINAL_2016-07-19.pdf
http://aldhistory.blogspot.
fi/2016/07/ald-2016-
travel-notes.html

26
ALD 2016 Dublin: Malygin invited talk + VPHA poster
VPHA manuscript + Baltic ALD 2016 St. Petersburg
62 authors, submitted Oct 30, 2016
http://aldhistory.blogspot.fi/search/label/JVSTA
Darker grey  more
VPHA contributors

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VPHA article published in the special ALD issue
 Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 35,
010801 (2017); doi: http://dx.doi.org/10.1116/1.4971389
 62 authors (alphabetical order)
 Was featured and most read for several months (now 2nd)
 VPHA reading is still open & we are collecting info on ALD theses,
reviews & conferences worldwide. Contact: info@vph-ald.com
 Add info through http://vph-ald.com/VPHAopenfiles.html

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ALD conformality testing
with microscopic lateral
structures
Lateral structures being developed
at VTT
 http://pillarhall.com
 Twitter: #TestedWithPillarHall
2

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VTT’s approach: all-silicon microscopic lateral
high-aspect-ratio structures – PillarHall® Proto3
15 mm
20mm
l
Si
(side view)
l
g =
Gao et al., J. Vac. Sci. Technol. A 33 (2015) 010601;
Mattinen et al., Langmuir 32 (2016) 10559;
Puurunen, Gao, IEEE Xplore,
http://ieeexplore.ieee.org/document/7886526/ .
Opening
w
AR 2 : 1 … 10 000 : 1
(small to ”infinite”)
= 1 to 5000 µm
200
to
1000 nm
PillarHall(R)

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PillarHall®: Multitude of analysis possibilities
Penetration depth
under membrane
~70 µm
AR ~140:1
Cross-section, SEM
(50 nm by ALD)
For scientific publications, see DOI 10.1116/1.4903941; DOI acs.langmuir.6b03007
More info to come in conference talks: Puurunen et al., EuroCVD 2017 & ALD 2017
Top-view microscopy
(50 nm by ALD)
Quick semiquantitative
(nondestructive) analysis
Traditional electron
microscopy cross-sections
Uniform coating all around
the feature, AR ~40:1,
gap height 500 nm

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PillarHall®: Remove top membrane to access
detailed, reproducible information of film on Si
Photo: Riikka Puurunen, VTT
Distance from LHAR opening (µm)
Reflectometry
Al2O3 ALD
For scientific publications, see: DOI
10.1116/1.4903941; DOI acs.langmuir.6b03007
More info to come in conference talks: Puurunen et al.,
EuroCVD 2017 & ALD 2017

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distance, aspect ratio
thickness • Optimise reaction times/doses
(tA, tB, pA, pB)
• Extract kinetic parameters
• Optimise purge times (tA2, tB2)
• Understand reaction mechanisms
PillarHall® line scans: route to understanding
and optimising process fundamentals

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Modelling outcome example
(not published, not final)
made by Markku Ylilammi/VTT
• Sticking coefficient 0.0108
• Equilibrium constant 51.3 Pa-1
• TMA partial pressure at inlet 93.4 Pa
(Manuscript preparation on-going)

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Imagine what all can be done with the chips!
 How uniform are the films actually inside the 3D structure?
 Composition?
 Morphology?
 Electrical properties?
 …
 What is the highest aspect ratio one can coat?
 What methods can be used for non-destructive analysis?
 What methods can be used for line scans & extracting kinetic
information?
 How will our understanding of ALD reactions evolve through
exposing a new parameter space for investigation?
”?!

16
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Imagine what all can be done with the chips!
 How uniform are the films actually inside the 3D structure?
 Composition?
 Morphology?
 Electrical properties?
 …
 What is the highest aspect ratio one can coat?
 What methods can be used for non-destructive analysis?
 What methods can be used for line scans & extracting kinetic
information?
 How will our understanding of ALD reactions evolve through
exposing a new parameter space for investigation?
”?!

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More test users for PillarHall chips welcome
- prototype development ongoing
 Academic partners
welcome: goal is joint
publications
 Conditions in Materials
Transfer Agreement (MTA)
 To get an idea, grab a
prototype brochure
 Or: have a look at the
PillarHall demo – it is
always with me!
 Email: pillarhall@vtt.fi
 Website: http://pillarhall.com

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Part 2: conformality analysis (with lateral
structures)
3
Link
* Full version in SlideShare

VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD
Comparison of interpretations on
the surface chemistry of the
Me3Al-H2O ALD process
ALD 2016 Ireland, July 2016
Riikka L. Puurunen
VTT Technical Reseach Centre of Finland, Ltd.

2R. L. Puurunen, ALD 2016, July 26, 2016
From: Puurunen, EuroCVD 2007 (in SlideShare)

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]”
995
1287
26
Cited
WoS
20.7.2016
2

 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
[Puurunen2005]
[George2010]
[Knapas2013]

[Puurunen2005]
 Puurunen et al., J. Phys. Chem. B 104 (2000) 6599
 Puurunen et al., Phys. Chem. Chem. Phys., 3 (2001) 1093
[Me]
Ccontent
Alcontent

[Puurunen2005]
Fitting reference: Puurunen,
Appl. Surf. Sci. 245 (2005) 6-10
 Quantitative explanation of GPC
vs temperature via loss of [OH]
and ~constant [Me]

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!

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Conclusion --- by Riikka, in Riika  (1/2)
The view on ALD’s history is changing
 Facts need to be right. Virtual Project on the History of
ALD still welcomes new volunteers  info@vph-ald.com
 No single full balanced historical review of ALD exists
currently. Good combination: (1) ALE and (3) ML essays
together, topped up with (3) the JVSTA 2017 review.
PillarHall conformality test structure development
 Interested in scientific/industrial POC studies?
 Please contact us (pillarhall@vtt.fi)
Room for scientific studies on surface chemistry of ALD
 Many ALD processes are used in industry, without
understanding the fundamental surface reaction chemistry

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Conclusion (1/2)
 Could ALD and Tuomo Suntola
get the
Millennium Technology Prize 2018?
 Let us propose it! DL end Jul
 Riikka) will write proposal & get CV
 Support letters from all over the
world are welcome and needed!
 Those wishing to support: please
send your letter either to
riikka.puurunen (at) aalto.fi, or
 Directly to Technology Academy
Finland (TAF)
Example support letter:

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Thank you, questions?
Atomikerroskasvatus
‫השקעת‬ ‫אטומיות‬ ‫שכבות‬
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

On the history and future of ALD: VPHA, conformality analysis, mechanisms

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