Researchers at Holst Centre managed to deposit both the semiconductor and dielectric layer of a TFT backplane using spatial atomic layer deposition (SALD). The backplane on a plastic foil was then combined with an OLED frontplane to obtain a 200-PPI QVGA display. The equipment used to produce the demonstrator is currently being commercialized by Holst Centre spin-off Saldtech, which completed a second investment round last May.
Backplane electronics for displays are typically sputtered. It’s possible to sputter on foils but the subsequent anneal step limits the choice of substrates. ALD features mild process conditions, allowing for a wider range of substrates to be used.
Additionally, ALD offers better control over material composition and layer thickness. Using SALD improves production throughput but also increases control over interface quality if multiple layers are deposited in succession. This, in turn, increases device performance.