1. Spatial Atomic Layer Deposition
Marco Baroncini
Good morning everyone, my name is Marco Baroncini and today I am going to talk about the spatial atomic layer deposition which is a technology based on the classical Atomic layer deposition

2. Problem:
ALD is based on two time-sequenced selective and self-limiting half-reactions, each one being separated by purge step.
ALD is a technique capable of producing ultrathin films, advantages:
Very high film quality
No particles, no pinholes
Thickness control at atomic level
Wide range of materials
Superior conformability
Disadvantages: SLOW RATE OF DEPOSITION (0.01 nm/s)
DOPO slow rate dire qualcosa al livello industriale come è un poroblema per la produzione

3. Spatial-ALD
Spatial separation of half-reactions, instead of time-separation
Combine the advantages of conventional ALD with high deposition rates (1,2 nm/s)
Efficient separation between the two half-reactions is needed
ALD
Discorso sul purge step.. Non è osoleto è rivisitato
Spatial-ALD
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012.

4. Spatial-ALD: spatial separation
Small height gap + high flow rates form excellent diffusion barriers
Gas-bearing technology: gap < 100µm
Dire che sono seprata da un gas generlamente N2 indicare il grafico a sinistra, Dire che il purge step è obsoleto , gap dire la dimensione dire perche è importante eliminare la diffusione sporicizia evitare reazioni non volute
No parasitic deposition, high precursor yield and atmospheric pressure
ADVANTAGI DI PULIZIA DEL REATTORE
High-speed spatial atomic-layer deposition of alluminum oxide layers for sola cell passivation; Paul boot et al.; 2010.

5. Rotating spatial ALD reactor:
Rigid substrates
Rotation of the substrate
Most important parameter: Growth Per Cycle (GPC)
GPC: 0.12 nm/cycle
At 600 rpm: 1.2 nm/s
Descrizione del apparato scrivere un modello da ”leggere”
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012.

6. Roll-to-roll, TNO approach:
Flexible substrates
Foil moves left to right injector rotates right to left
Gas-bearings keep the foil at a fixed distance
Total thickness: rotation frequency of the drum + translation speed of the foil
Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek (TNO; English: Netherlands Organisation for Applied Scientific Research) is a nonprofit company in the Netherlands that focuses on applied science.
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012.

7. Conclusions: S-ALD has high growth rate: 1nm/s
Maintain the advantages of the ALD
Possibility of high volume of production
Deposition on flexible and rigid substrates
Operation under atmospheric pressure

8. References:
High-speed spatial atomic-layer deposition of alluminum oxide layers for sola cell passivation; Paul boot et al.; Advanced Materials; 2010.
Oxide electronics by Spatial Atomic Layer Deposition; David H. Levy et al.; Journal of display technology; 2009.
Spatial atomic layer deposition of zinc oxide thin films; A. Illiberi, F. Roozeboom and P. Pooldt; Applied materials & interfaces; 2011.
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; Journal of vacuum science & technology (JVSTA); 2012.

9. Information Slides

10. Atomic Layer Deposition
ALD is a variant of CVD in which a substrate is exposed to an alternating sequence of reactant gases.
First half reaction
Purge
Second half reaction
Repeat
Advantages:
Very high film quality
No particles no pinholes
Thickness control on atomic scale
Superior conformability
Wide range of materials
Disadvantages:
Very very slow: 0.01nm/s

11. ALD: industrial applications
Conventional ALD is not always compatible with industrial needs due to the slow rate of deposition.
The industrial application of the technique is mainly limited to CMOS semiconductor processing of transistor gate oxide and DRAM capacitors.
Target: Increase the rate of deposition
Spatial Atomic Layer Deposition

12. Spatial-ALD: spatial separation
This technique is based on spatial separation of half-reactions, instead of time-separated. Spatial-ALD rate: 1,0-1,2 nm/s
Conventional ALD b)Spatial ALD
The point Q can move approaching
different gasses
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012
Oxide electronics by Spatial Atomic Layer Deposition; David H. Levy et al.; Journal of display technology; 2009

13. Spatial-ALD: Spatial separation
The half reactions are separated using a combination of physical barriers and continuously flowing purge steams to prevent the inter diffusion and mixing of precursors.
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012.

14. Spatial-ALD: gap
To achieve an optimized separation between the two reactant gases is very important to consider the gap between the substrates and the gas inlets.
Large gap: Low pressure and significant gas mixing
Small gap: Large pressure and effective gas separation
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012

15. Spatial-ALD: Gas-bearing
The gas-bearing technology guarantees a very small gap: <100µm
In this system the gas used for the gas-bearing system is also the gas used for separate the two reactant, for instance 𝑁 2 .
High-speed spatial atomic-layer deposition of alluminum oxide layers for sola cell passivation; Paul boot et al.; 2010.

16. Spatial-ALD: Gas-bearing Advantages
The pressure fields are much stronger, forcing the gas emitted from an inlet slot to flow only to the adjacent exhaust slots.
The effective chamber size is very small, leading to high turnover rates for each channel and thus improve gas isolation.
Completely seal off the reaction zones, making the reactor completely independent from the environment, enabling operation under atmospheric pressure.

17. Rotating S-ALD reactor
The separate reaction zones inlets are incorporated in a round reactor head, surrounded and separated by gas-bearing planes
The most important parameter is the Growth Per Cycle (GPC)
T=400°C, P= 1atm
Homogeneous deposition
GPC=0,12nm/cycle, Rotational speeds= 600rpm, Growth rate= 1,2 nm/s
High-speed spatial atomic-layer deposition of alluminum oxide layers for sola cell passivation; Paul boot et al.; Advanced Materials; 2010.

18. Growth per cycle (GPC)
Film thickness increases linearly with the number of rotation indicating that films have been grown by an ALD mode.
𝐺𝑃 𝐶 𝑍𝑛𝑂 =0,18 𝑛𝑚 𝑐𝑦𝑐𝑙𝑒
The partial pressure of precursors, together with the exposure time (rotation frequencies) determine the GPC.
There’s a threshold which represents the self-saturating growth of the precursors.
Spatial atomic layer deposition of zinc oxide thin films; A. Illiberi, F. Roozeboom and P. Pooldt; Applied materials & interfaces; 2011.

19. Rotating S-ALD reactor
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012.

20. Roll-to-roll reactor: flexible surfaces
Central drum that contains several half- reaction zones separated and surrounded by nitrogen gas bearings
Gas bearings ensure that the foil is kept at a fixed distance from the surface of the drum
Total thickness is determined by the total number of half reaction zone pairs that the foil passes
No mechanical contact between the deposition side of the foil and the reactor
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012.

21. Roll-to-roll reactor: Layout

22. Applications: Oxide electronics Solar cells Organic electronics
Flexible electronics

23. References
High-speed spatial atomic-layer deposition of alluminum oxide layers for sola cell passivation; Paul boot et al.; Advanced Materials; 2010.
Oxide electronics by Spatial Atomic Layer Deposition; David H. Levy et al.; Journal of display technology; 2009.
Spatial atomic layer deposition of zinc oxide thin films; A. Illiberi, F. Roozeboom and P. Pooldt; Applied materials & interfaces; 2011.
Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; Journal of vacuum science & technology (JVSTA); 2012.