(Invited) Low-Temperature Processed and Self-Aligned InGaZnO Thin-Film Transistor with an Organic Gate Insulator for Flexible Device Applications

Abstract

Recently, metal-oxide thin-film transistors (TFTs) have attracted considerable attention for use in next-generation flat panel displays. An amorphous InGaZnO (IGZO) semiconductor is widely accepted as a promising channel material for TFT applications owing to its outstanding electrical properties. Moreover, since oxide semiconductor can be deposited even at room temperature by sputtering, it is recognized as a promising material for flexible device applications. From the standpoint of flexible devices, an organic insulating material is a good candidate for gate insulator (GI) even for the oxide thin-film transistors (TFTs). In this presentation, a self-aligned and top-gated IGZO TFT with an organic gate insulator was demonstrated at a maximum processing temperature of 150 ºC. First, the controlling methods of the hybrid interface between the InGaZnO channel and the organic gate insulator were investigated. It was demonstrated that an organic protection layer of the IGZO channel and controlling the oxygen content in the IGZO channel are effective to achieve good performance TFTs at low processing temperature; however, it was also revealed that an excess oxygen acted as an electron trap existing at the IGZO/GI interface and degraded the TFT’s reliability. Second, carrier concentration in the IGZO was selectively controlled by helium plasma treatment with a substrate bias for source and drain (S/D) regions of self-aligned TFT. It was revealed that lateral diffusion from S/D extension to the IGZO channel was influenced by the doping methods. We achieved a self-aligned and top-gated IGZO TFT with an organic gate insulator that was fabricated at a maximum processing temperature of 150 ºC. Field effect mobility of over 10 cm2/Vs and subthreshold swing of below 0.2 V/dec. have been obtained. Details will be discussed at the conference.