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.
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 language | English |
|---|---|
| Number of pages | 1 |
| Publication status | Published - 30 Jul 2018 |
| MoE publication type | Not Eligible |
| Event | 18th 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 2018 → 1 Aug 2018 https://ald2018.avs.org/ |
Conference
| Conference | 18th International Conference on Atomic Layer Deposition, ALD/ALE 2018 |
|---|---|
| Abbreviated title | ALD/ALE 2018 |
| Country/Territory | Korea, Republic of |
| City | Incheon |
| Period | 29/07/18 → 1/08/18 |
| Internet address |