Atomic layer dielectric deposition for flexible organic transistors

Abstract

Atomic layer deposition (ALD) of thin film high-k oxides has been demonstrated for low voltage thin film transistors (TFT). However, for organic semiconductors, the transistors are based on a bottom-gate architecture. We have developed an oxide growth process for a top-gate transistor architecture for organic thin film semiconductors based on the ALD process, plasma-enhanced as well as thermal. The ALD growth process is self-limiting and this implies that the film thickness is dependent only on the number of deposition cycles. Practically, this creates accurate and uniform conformal thickness control over large areas. Furthermore, thickness control leads to good reproducibility and straightforward scale-up. We will discuss our low temperature (150C) Al2O3 growth process by plasma assisted-ALD compared to the thermal process on flexible plastic substrates. Also, oxide characterization as well as top-gated TFT performance enabled by different buffer layers between the semiconductor and ALD dielectric will be presented. The top-gate oxide growth process enabled the fabrication of more complex circuits such as a decoder.