Roll-to-roll atomic layer deposition process for flexible electronics encapsulation applications

Abstract

At present flexible electronic devices are under extensive development and, among them, flexible organic light-emitting diode displays are the closest to a large market deployment. One of the remaining unsolved challenges is high throughput production of impermeable flexible transparent barrier layers that protect sensitive light-emitting materials against ambient moisture. The present studies deal with the adaptation of the atomic layer deposition (ALD) process to high-throughput roll-to-roll production using the spatial ALD concept. We report the development of such a process for the deposition of 20 nm thickness Al2O3 diffusion barrier layers on 500 mm wide polymer webs. The process uses trimethylaluminum and water as precursors at a substrate temperature of 105 °C. The observation of self-limiting film growth behavior and uniformity of thickness confirms the ALD growth mechanism. Water vapor transmission rates for 20 nm Al2O3 films deposited on polyethylene naphthalate (PEN) substrates were measured as a function of substrate residence time, that is, time of exposure of the substrate to one precursor zone. Moisture permeation levels measured at 38 °C/90% relative humidity by coulometric isostatic–isobaric method were below the detection limit of the instrument (<5 × 10−4 g/m2 day) for films coated at web moving speed of 0.25 m/min. Measurements using the Ca test indicated water vapor transmission rates ∼5 × 10−6 g/m2 day. Optical measurements on the coated web showed minimum transmission of 80% in the visible range that is the same as the original PEN substrate.

Addressing Interfacial Issues in Liquid-Based and Solid-State Batteries by Atomic and Molecular Layer Deposition

“…(7) ALD/MLD reactors with rotary and roll-to-roll functions have been developed for large-scale particle samples and flexible substrate in the past years. [125][126][127][128] These features will facilitate the scale-up of interfacial modifications and battery fabrication for SSBs by ALD/MLD.…”

Bio‐based multilayer barrier films by extrusion, dispersion coating and atomic layer deposition

“…ALD thin films have typically been produced with single wafer or batch processes at low pressures, which limits its throughput on large area applications. However, recently there have been an increasing number of activities related to roll‐to‐roll and atmospheric ALD processes . A thin ALD coating does not impair disintegration of PLA film or coated board in compost, and polymer granules deposited with such coatings have been melt processed into composites indicating certain level of recyclability …”

Spatial atomic layer deposition: Performance of low temperature H2O and O3 oxidant chemistry for flexible electronics encapsulation

“…5 Spatial ALD utilizes an alternative approach to batch ALD where a moving substrate is alternatively exposed to active and inert gas zones in a way that replicates the exposure sequence of conventional ALD cycle. The recently developed spatial ALD (SALD) concept allows such a process to be implemented.…”