Single-crystalline silicon nanomembrane thin-film transistors with anodized aluminum oxide as a gate dielectric on rigid and flexible substrates

Abstract

Flexible integrated circuits have gained a lot of attention in recent years for their emerging applications in wearable electronics. Flexible thin-film transistors (TFTs) with low-costs and high-performance are highly desirable as essential and fundamental elements for most flexible applications. In this paper, we fabricate single-crystalline silicon nanomembrane (SiNM)-based TFTs with anodized aluminum oxide (AAO) as a dielectric material on glass and flexible plastic substrates. Good quality AAO was obtained on plastic substrates at room temperature. Atomic force microscopy (AFM)was used for the surface morphology of the AAO gate dielectric layers on different substrates (i.e. glass, polyethylene terephthalate (PET), and SU-8 coated PET). The electrical characteristics of the AAO gate dielectric layers on different substrates were also analyzed with metal–insulator–metal capacitors. The SiNMs were processed with a complementary metal oxide semiconductor (CMOS) compatible semiconductor process (e.g. photolithography, ion implantation, thermal annealing, reactive ion etching, metal evaporation, etc), and then transferred to the substrates with AAO/aluminum stack layers. The performance of the transistors on glass and plastic substrates was characterized. Compared with the TFT fabricated on a glass substrate, the TFT fabricated directly on a PET substrate had lower performance due to poor surface roughness. For optimization of the surface roughness, the PET was modified with a coating of SU-8 photoresist. In this way, the TFT had properties close to that on a glass substrate. AAO that can be manufactured at room temperature provides a simple and low-cost solution for high-performance flexible single-crystalline SiNM TFTs.