Scalable High-Speed Hybrid Complementary Integrated Circuits based on Solution-Processed Organic and Inorganic Transistors

Abstract

Printed electronics offer a cost-efficient way to realise flexible electronic devices. The combined use of p-type and n-type semiconductors would yield silicon-like integrated circuits with low power consumption and stability. However, printing complementary circuits is challenging due to a lack of suitable material systems. To counter this, we employed a hybrid system to integrate p-type organic semiconductors (OSCs) and n-type amorphous metal oxide semiconductors (MOSs). These damage-free patterned OSC- and MOS-based thin-film transistors with improved process durability allowed the fabrication of hybrid complementary circuits on flexible substrates. These inverters functioned well even after exposure to air for 5 months. A large noise margin and power gain of 38 were realised with a supply voltage as low as 7 V. Furthermore, a five-stage ring oscillator with a stage propagation delay of 1.3 µs was achieved, which is the fastest operation ever reported for printed, flexible complementary inverters.

Review of recent trends in flexible metal oxide thin-film transistors for analog applications

“…However, these devices also withstood 50,000 bending cycles over a 10 mm bending radius, while presenting a decrease of the maximum drain current down to 53 % of its original value. Other flexible short-channel metal oxide TFTs presented in literature also demonstrated a negative V TH shift under tensile bending radii down to 3 mm [61,94,107]. Finally, metal oxide TFTs on rigid substrates have exhibited f t above 10 GHz [67] and intrinsic gains of 29 000 [116], demonstrating the potential of metal oxide TFTs for high-frequency and high-gain operation.…”

“…A second challenge is represented by the development of solution-processing (or even printing) techniques able to realize metal oxide semiconductor TFTs, circuits and systems over large areas and cost-effectively. Here, the recent demonstration of solution-processed TFTs with transit frequencies of 23 MHz [107] shows some promising trends. Additionally, other new techniques such as adhesion lithography, plasma treatment, or heterogeneous multi layer semiconductor structures deserve further evaluation concerning their AC performance implications.…”

“…In addition, while the aforementioned configurations are dominated by vacuum-processed semiconductor layers -mainly Indium-Gallium-Zinc-Oxide (IGZO) as shown in table 1 -, solution-processed TFTs have also been demonstrated [92,103,107,114] with reports of transit frequencies as high as 23 MHz for flexible Indium-Zinc-Oxide (IZO) devices [107]. Besides IGZO, IZO and Indium-Oxide, short-channel TFTs with Indium-Tin-Oxide (ITO) [28], Zinc-Oxide (ZnO) [109] and Indium-Tin-Zinc-Oxide (ITZO) [82] have also been shown.…”

“…In addition, the presented devices maintained an I ON /I OFF ratio above 10 5 , thanks to the replacement of the PI spacer by Zenocoat. Recently, short-channel and high-frequency solution-processed IZO TFTs have also been shown on flexible substrates [107]. These devices were fabricated through standard photolithography but used a mild etchant (aqueous Na 2 CO 3 ), to avoid damage to the solution-processed semiconductor layer.…”

“…These devices were fabricated through standard photolithography but used a mild etchant (aqueous Na 2 CO 3 ), to avoid damage to the solution-processed semiconductor layer. Through this method, Wei et al demonstrated an unprecedented f t of 23 MHz for 1.7 µm long devices [107]. This development, together with novel ultra-thin, high-k dielectric layers fabricated through high-throughput printing methods indicate that fully printed flexible metal oxide devices and circuits are becoming increasingly more viable [103].…”