Fully spin-coated memory TFT

Abstract

The trends of recent technology are moving towards building system on panel (SOP), system on glass (SOG) or `see through' display technologies as well as towards large area flexible electronics with cost effective process[1]-[2]. Therefore the technologists are focused on developing fully spin-coated low cost sol-gel Thin Film Transistor (TFT) with solution processed Indium Gallium Zinc Oxide (IGZO) as a semiconductor[3]. It is necessary to develop transparent memory TFT by complete low cost sol-gel spin-coating technique which is suitable for large area electronics. There are several reports on transparent memory technology with IGZO as channel layer. However, most of them are fabricated with sophisticated ultra-high vacuum technique or high temperature deposition. In addition, some memory devices are only UV-erasable (not electrically) [4]. Since most of the spin-coated dielectrics are not as good as films deposited by other techniques i.e. sputtering, e-beam deposition, Atomic Layer Deposition (ALD) etc, preventing memory leakage is very difficult. Recently, we demonstrated fully spin-coated two terminal capacitive memory devices with Aluminium Oxide Phosphate (ALPO) as a dielectric and Cadmium Telluride nanoparticle (CdTe-NP) as a charge storage centre [5]. However, these structures can be useful only for SOP or SOG technology and not suitable for flexible electronics due to the high temperature processing steps. Here, we demonstrate a fully sol-gel spin-coated electrically programmable (P/E) memory three terminal TFT device (without silicon technology) with sol-gel IGZO as a deep level charge storage centre as well as channel layer. ALPO was used as tunnelling and blocking layer to prevent the memory leakage. The entire processing was carried out in the normal lab environment with the temperature processing step as low as 350°C.