Spatial Atomic Layer Deposition Marco Baroncini 10-3-2016 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

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 http://npl-web.stanford.edu/archive/energy/micro-fuel-cell/sofc/electrode/ald/

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.

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.

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.

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.

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

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.

Information Slides

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

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

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

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.

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

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.

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.

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.

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.

Rotating S-ALD reactor https://www.youtube.com/watch?v=8ljvULeyiBs Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition; Paul Poodt, et al.; 2012.

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.

Roll-to-roll reactor: Layout https://www.youtube.com/watch?v=PS65f635L8w

Applications: Oxide electronics Solar cells Organic electronics Flexible electronics

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.