Mechanisms limiting conformality in thermal and plasma-assisted ALD investigated by Lateral High Aspect Ratio structures

Mikko Utriainen, Feng Gao, Riikka L. Puurunen, Karsten Arts (Corresponding author), Vincent Vandalon, Erwin Kessels, Harm Knoops

Research output: Contribution to conferenceConference AbstractScientificpeer-review

Abstract

This work investigates the processes governing conformality achieved by
ALD, using Lateral High Aspect Ratio (LHAR) test structures supplied by
VTT.1
We show that these structures are well suitable for investigating the
underlying ALD chemistry, as the shape of the thickness profile and the
penetration depth are indicative for the growth regime and provide insight
into parameters such as sticking probabilities.
In the new PillarHall™ LHAR3 structures the reacting species diffuse
underneath a removable membrane which is supported by pillars giving a
500 nm spacing. This configuration offers new possibilities compared to
traditional vertical structures. Among others, top-view diagnostics can be
applied to straightforwardly determine the thickness profile and material
properties. A range of diagnostics is validated in this work for this top-view
analysis. Moreover, the structure has features with aspect ratios up to
10000. Therefore a non-fully saturated profile is acquired for even the most
conformal processes, which provides information on the limiting
mechanisms.
Two cases are discussed to exemplify these possibilities. Firstly, in the case
of thermal ALD of Al2O3 using TMA and water it is known from recent work
that at low temperatures the growth is limited by the reduced reactivity of
H2O towards –CH3 groups.2
We examine how this reactivity affects the
conformality, by measuring and simulating Al2O3 thickness profiles for
different substrate temperatures. For example, at 200°C table temperature
a sloping profile is observed with a half-thickness-penetration-depth
(HTPD) of ~400 μm (AR=800). This profile seems to be consistent with the
low sticking probability of water at these temperatures (s~3·10-5).2
That is,
from Monte Carlo simulations a growth regime in between reaction-limited
and diffusion-limited growth is expected for this sticking probability and
penetration depth, yielding such a sloping profile.
Secondly, in the case of plasma-assisted ALD of Al2O3 recombinationlimited growth is observed, as the HTPD is reduced to ~30 µm (AR=60)
through recombination of the reactive O radicals. As even these short
profiles can be resolved using top-view diagnostics, the LHAR3 structures
can be employed to investigate recombination probabilities in plasmaassisted ALD as well. On the basis of the aforementioned studies, these and
other insights into ALD chemistry relevant to conformal growth will be
provided.
Original languageEnglish
Number of pages1
Publication statusPublished - 30 Jul 2018
MoE publication typeNot Eligible
Event18th International Conference on Atomic Layer Deposition, ALD/ALE 2018: Featuring the 5th International Atomic Layer Etching Workshop - Songdo Convensia in Incheon, Incheon, Korea, Republic of
Duration: 29 Jul 20181 Aug 2018
https://ald2018.avs.org/

Conference

Conference18th International Conference on Atomic Layer Deposition, ALD/ALE 2018
Abbreviated titleALD/ALE 2018
CountryKorea, Republic of
CityIncheon
Period29/07/181/08/18
Internet address

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high aspect ratio
profiles
penetration
reactivity
chemistry
water
aspect ratio
spacing
membranes
temperature
configurations
simulation

Cite this

Utriainen, M., Gao, F., Puurunen, R. L., Arts, K., Vandalon, V., Kessels, E., & Knoops, H. (2018). Mechanisms limiting conformality in thermal and plasma-assisted ALD investigated by Lateral High Aspect Ratio structures. Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.
Utriainen, Mikko ; Gao, Feng ; Puurunen, Riikka L. ; Arts, Karsten ; Vandalon, Vincent ; Kessels, Erwin ; Knoops, Harm. / Mechanisms limiting conformality in thermal and plasma-assisted ALD investigated by Lateral High Aspect Ratio structures. Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.1 p.
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abstract = "This work investigates the processes governing conformality achieved byALD, using Lateral High Aspect Ratio (LHAR) test structures supplied byVTT.1 We show that these structures are well suitable for investigating theunderlying ALD chemistry, as the shape of the thickness profile and thepenetration depth are indicative for the growth regime and provide insightinto parameters such as sticking probabilities.In the new PillarHall™ LHAR3 structures the reacting species diffuseunderneath a removable membrane which is supported by pillars giving a500 nm spacing. This configuration offers new possibilities compared totraditional vertical structures. Among others, top-view diagnostics can beapplied to straightforwardly determine the thickness profile and materialproperties. A range of diagnostics is validated in this work for this top-viewanalysis. Moreover, the structure has features with aspect ratios up to10000. Therefore a non-fully saturated profile is acquired for even the mostconformal processes, which provides information on the limitingmechanisms.Two cases are discussed to exemplify these possibilities. Firstly, in the caseof thermal ALD of Al2O3 using TMA and water it is known from recent workthat at low temperatures the growth is limited by the reduced reactivity ofH2O towards –CH3 groups.2 We examine how this reactivity affects theconformality, by measuring and simulating Al2O3 thickness profiles fordifferent substrate temperatures. For example, at 200°C table temperaturea sloping profile is observed with a half-thickness-penetration-depth(HTPD) of ~400 μm (AR=800). This profile seems to be consistent with thelow sticking probability of water at these temperatures (s~3·10-5).2 That is,from Monte Carlo simulations a growth regime in between reaction-limitedand diffusion-limited growth is expected for this sticking probability andpenetration depth, yielding such a sloping profile.Secondly, in the case of plasma-assisted ALD of Al2O3 recombinationlimited growth is observed, as the HTPD is reduced to ~30 µm (AR=60)through recombination of the reactive O radicals. As even these shortprofiles can be resolved using top-view diagnostics, the LHAR3 structurescan be employed to investigate recombination probabilities in plasmaassisted ALD as well. On the basis of the aforementioned studies, these andother insights into ALD chemistry relevant to conformal growth will beprovided.",
author = "Mikko Utriainen and Feng Gao and Puurunen, {Riikka L.} and Karsten Arts and Vincent Vandalon and Erwin Kessels and Harm Knoops",
year = "2018",
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Utriainen, M, Gao, F, Puurunen, RL, Arts, K, Vandalon, V, Kessels, E & Knoops, H 2018, 'Mechanisms limiting conformality in thermal and plasma-assisted ALD investigated by Lateral High Aspect Ratio structures' 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of, 29/07/18 - 1/08/18, .

Mechanisms limiting conformality in thermal and plasma-assisted ALD investigated by Lateral High Aspect Ratio structures. / Utriainen, Mikko; Gao, Feng; Puurunen, Riikka L.; Arts, Karsten (Corresponding author); Vandalon, Vincent; Kessels, Erwin; Knoops, Harm.

2018. Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.

Research output: Contribution to conferenceConference AbstractScientificpeer-review

TY - CONF

T1 - Mechanisms limiting conformality in thermal and plasma-assisted ALD investigated by Lateral High Aspect Ratio structures

AU - Utriainen, Mikko

AU - Gao, Feng

AU - Puurunen, Riikka L.

AU - Arts, Karsten

AU - Vandalon, Vincent

AU - Kessels, Erwin

AU - Knoops, Harm

PY - 2018/7/30

Y1 - 2018/7/30

N2 - This work investigates the processes governing conformality achieved byALD, using Lateral High Aspect Ratio (LHAR) test structures supplied byVTT.1 We show that these structures are well suitable for investigating theunderlying ALD chemistry, as the shape of the thickness profile and thepenetration depth are indicative for the growth regime and provide insightinto parameters such as sticking probabilities.In the new PillarHall™ LHAR3 structures the reacting species diffuseunderneath a removable membrane which is supported by pillars giving a500 nm spacing. This configuration offers new possibilities compared totraditional vertical structures. Among others, top-view diagnostics can beapplied to straightforwardly determine the thickness profile and materialproperties. A range of diagnostics is validated in this work for this top-viewanalysis. Moreover, the structure has features with aspect ratios up to10000. Therefore a non-fully saturated profile is acquired for even the mostconformal processes, which provides information on the limitingmechanisms.Two cases are discussed to exemplify these possibilities. Firstly, in the caseof thermal ALD of Al2O3 using TMA and water it is known from recent workthat at low temperatures the growth is limited by the reduced reactivity ofH2O towards –CH3 groups.2 We examine how this reactivity affects theconformality, by measuring and simulating Al2O3 thickness profiles fordifferent substrate temperatures. For example, at 200°C table temperaturea sloping profile is observed with a half-thickness-penetration-depth(HTPD) of ~400 μm (AR=800). This profile seems to be consistent with thelow sticking probability of water at these temperatures (s~3·10-5).2 That is,from Monte Carlo simulations a growth regime in between reaction-limitedand diffusion-limited growth is expected for this sticking probability andpenetration depth, yielding such a sloping profile.Secondly, in the case of plasma-assisted ALD of Al2O3 recombinationlimited growth is observed, as the HTPD is reduced to ~30 µm (AR=60)through recombination of the reactive O radicals. As even these shortprofiles can be resolved using top-view diagnostics, the LHAR3 structurescan be employed to investigate recombination probabilities in plasmaassisted ALD as well. On the basis of the aforementioned studies, these andother insights into ALD chemistry relevant to conformal growth will beprovided.

AB - This work investigates the processes governing conformality achieved byALD, using Lateral High Aspect Ratio (LHAR) test structures supplied byVTT.1 We show that these structures are well suitable for investigating theunderlying ALD chemistry, as the shape of the thickness profile and thepenetration depth are indicative for the growth regime and provide insightinto parameters such as sticking probabilities.In the new PillarHall™ LHAR3 structures the reacting species diffuseunderneath a removable membrane which is supported by pillars giving a500 nm spacing. This configuration offers new possibilities compared totraditional vertical structures. Among others, top-view diagnostics can beapplied to straightforwardly determine the thickness profile and materialproperties. A range of diagnostics is validated in this work for this top-viewanalysis. Moreover, the structure has features with aspect ratios up to10000. Therefore a non-fully saturated profile is acquired for even the mostconformal processes, which provides information on the limitingmechanisms.Two cases are discussed to exemplify these possibilities. Firstly, in the caseof thermal ALD of Al2O3 using TMA and water it is known from recent workthat at low temperatures the growth is limited by the reduced reactivity ofH2O towards –CH3 groups.2 We examine how this reactivity affects theconformality, by measuring and simulating Al2O3 thickness profiles fordifferent substrate temperatures. For example, at 200°C table temperaturea sloping profile is observed with a half-thickness-penetration-depth(HTPD) of ~400 μm (AR=800). This profile seems to be consistent with thelow sticking probability of water at these temperatures (s~3·10-5).2 That is,from Monte Carlo simulations a growth regime in between reaction-limitedand diffusion-limited growth is expected for this sticking probability andpenetration depth, yielding such a sloping profile.Secondly, in the case of plasma-assisted ALD of Al2O3 recombinationlimited growth is observed, as the HTPD is reduced to ~30 µm (AR=60)through recombination of the reactive O radicals. As even these shortprofiles can be resolved using top-view diagnostics, the LHAR3 structurescan be employed to investigate recombination probabilities in plasmaassisted ALD as well. On the basis of the aforementioned studies, these andother insights into ALD chemistry relevant to conformal growth will beprovided.

M3 - Conference Abstract

ER -

Utriainen M, Gao F, Puurunen RL, Arts K, Vandalon V, Kessels E et al. Mechanisms limiting conformality in thermal and plasma-assisted ALD investigated by Lateral High Aspect Ratio structures. 2018. Abstract from 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018, Incheon, Korea, Republic of.