Oral presentation (O091) at the ALD 2016 Ireland conference, http://ald2016.com/ Abstract: Comparison of interpretations on the surface chemistry of the trimethylaluminiumwater ALD process Author: Riikka Puurunen VTT Technical Research Centre of Finland, Espoo, Finland The trimethylaluminium-water process to grow aluminium oxide by atomic layer deposition (ALD) was published in 1989 by Higashi and Fleming [1] and has since then become the most widely studied ALD process [2]. In addition to being widely applied, its surface chemistry has been reviewed in 2005 [3], and the process has been in several works considered as a model system of ALD [4, 5, 6]. Some fundamental questions regarding the surface chemistry of any ALD process are: 1. How does the growth per cycle (GPC) vary with temperature? (à What is the “ALD window” of the process?) 2. What defines the GPC? (à What is the limiting factor that causes saturation?) 3. Which surface reaction mechanisms take place? (à How fast are they?). A model system deserves an especially careful comparison of answers obtained in different studies to the above questions. This presentation reviews published data and show that different works explain the variation in GPC with temperature in significantly different ways. A summary of the interpretations is shown in Table 1. As a consequence, in the author’s opinion, one cannot currently conclude that general agreement would exist regarding the reaction mechanisms of this “model” ALD system. Table 1. Some growth chemistry interpretations related to the TMA-water “model” process made in three review articles Characteristic Ref. 3 Ref. 4 Ref. 5 Change of surface [Me] vs temperature in the experimental “background data” ~constant decreases increases Description of GPC change with temperature Decreases with * decreasing [OH], * while [Me] ~constant Decreases with * decreasing [OH], * decreasing [Me] (* n/z ~constant at 1.5) Explanation of less-thanmonolayer GPC & temperature trend Quantitative Qualitative - Acknowledgements: Funding came from the Finnish Centre of Excellence in Atomic Layer Deposition. References: [1] Higashi, Fleming, Appl. Phys. Lett. 55 (1989) 1963-1965. [2] Miikkulainen, Leskelä, Ritala, Puurunen, J. Appl. Phys. 113 (2013) Art. 021301 (101 p.). [3] Puurunen, J. Appl. Phys. 97 (2005) Art. 121301 (52 p.). [4] George, Chem. Rev. 110 (2010) 111-131. [5] Knapas, Ritala, Crit. Rev. Solid State Mater. Sci. 38 (2013) 167-202. [6] Weckman, Laasonen, Phys. Chem. Chem. Phys. 17 (2015) 17322-17334.

1. 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.

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

3. 3R. L. Puurunen, ALD 2016, July 26, 2016
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
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WoS
20.7.2016
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4. 4R. L. Puurunen, ALD 2016, July 26, 2016
 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

5. 5R. L. Puurunen, ALD 2016, July 26, 2016
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]

6. 6R. L. Puurunen, ALD 2016, July 26, 2016
From: Puurunen, EuroCVD 2007 (in SlideShare)
[Puurunen2005]

7. 7R. L. Puurunen, ALD 2016, July 26, 2016
[Puurunen2005]
 Puurunen et al., J. Phys. Chem. B 104 (2000) 6599
 Puurunen et al., Phys. Chem. Chem. Phys., 3 (2001) 1093
From: Puurunen, EuroCVD 2007 (in SlideShare)
[Me]
Ccontent
Alcontent

8. 8R. L. Puurunen, ALD 2016, July 26, 2016
[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)

9. 9R. L. Puurunen, ALD 2016, July 26, 2016
[George2010]
”
”

10. 10R. L. Puurunen, ALD 2016, July 26, 2016
Data behind the conclusion: annealing experiment
300C100C
[Me]
[George2010]
Room-temperature exposure!
Qualitative description of GPC
vs temperature via loss of [OH]
and loss of [Me]

11. 11R. L. Puurunen, ALD 2016, July 26, 2016
[Knapas2013]
• No explanation for
temperature trends of GPC
• n/z value considered as
mechanism, weak trend
with temperature (if any)
• discussion on H2O dose
”
”

12. 12R. L. Puurunen, ALD 2016, July 26, 2016
Data behind, [Me]: QCM and QMS studies ref. 108
Ref 108
 Water not saturated (?)
 Was Me3Al saturated?
[Me]
[Knapas2013]

13. 13R. L. Puurunen, ALD 2016, July 26, 2016
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]

14. 14R. L. Puurunen, ALD 2016, July 26, 2016
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!

15. 15R. L. Puurunen, ALD 2016, July 26, 2016
Acknowledgements
Funding: Academy of Finland,
Finnish Centre of Excellence on Atomic Layer Deposition
Presentation at: 98th Canadian Chemistry Conference, Ottawa,
June 14, 2015 (Surface Chemistry for Thin Film Deposition
Session)
Discussion in: Ylivaara et al. Thin Solid Films 552 (2014) 124-135
(Section, 5.1 ALD Growth)
Contact: riikka.puurunen@ vtt.fi

16. 16R. L. Puurunen, ALD 2016, July 26, 2016
Thank You!
Atomikerroskasvatus
‫השקעת‬ ‫אטומיות‬ ‫שכבות‬
εναπόθεση ατομικού στρώματος
Atomlagenabscheidung
Parmanu Parat Nishepan
परमाणु परत �न�ेपण
Deposizione a Strati Atomici
原子層堆積
원자층증착
आिण्वक 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

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