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

摘要

Atomic Layer Deposition (ALD) is the technology of choice where very thin and highqualityfilms are required. Its advantage is its ability to deposit dense and pinhole-freecoatings in a controllable manner. It has already shown promising results in a range ofapplications, e.g. diffusion barrier coatings for OLED displays, surface passivation layersfor solar panels. Spatial Atomic Layer Deposition (SALD) is a concept that allows adramatic increase in ALD throughput. During the SALD process, the substrate movesbetween spatially separated zones filled with the respective precursor gases and reagentsin such a manner that the exposure sequence replicates the conventional ALD cycle.The present work describes the development of a high-throughput ALD process.Preliminary process studies were made using an SALD reactor designed especially for thispurpose. The basic properties of the ALD process were demonstrated using the wellstudiedAl2O3 trimethyl aluminium (TMA)+H2O process. It was shown that the SALDreactor is able to deposit uniform films in true ALD mode. The ALD nature of the processwas proven by demonstrating self-limiting behaviour and linear film growth. The processbehaviour and properties of synthesized films were in good agreement with previous ALDstudies. Issues related to anomalous deposition at low temperatures were addressed as well.The quality of the coatings was demonstrated by applying 20 nm of the Al2O3 on topolymer substrate and measuring its moisture barrier properties. The results of testsconfirmed the superior properties of the coatings and their suitability for flexibleelectronics encapsulation. Successful results led to the development of a pilot scale roll-to-roll coating system. It wasdemonstrated that the system is able to deposit superior quality films with a watertransmission rate of 5x10-6 g/m2day at a web speed of 0.25 m/min. That is equivalent to aproduction rate of 180 m2/day and can be potentially increased by using wider webs.State-of-art film quality, high production rates and repeatable results make SALD thetechnology of choice for manufacturing ultra-high barrier coatings for flexible electronics.