Electrode adaptive thin film integrated logic circuits
Journal
IEEE T ELECTRON DEV
Date
2019.01.22
Abstract
Amorphous oxide based thin film logic circuits have been fabricated by using only n-type silicon-zinc-tin-oxide (a-SZTO) semiconducting channel layer with different source/drain electrode. Enhancement mode thin film transistors (TFTs) were fabricated with the oxide electrodes of indium-silicon-oxide (ISO) or indium-tin-oxide (ITO). Depletion mode TFTs were fabricated simply with different metal electrodes of titanium/aluminium (Ti/Al). Energy levels were measured by a Kelvin probe microscopy. The contact energy barrier heights between the channel layer and the electrode were measured to be about 1.831, 2.341, and 2.339 eV of Ti/Al electrode, ISO electrode, and ITO electrode, respectively. The physical mechanism on the change of the sheet and the contact resistance has been investigated using transmission line method (TLM) with different space of electrodes, systematically and proposed the change of the resistances is closely related with the barrier height. The inverters (NOT logic circuits) were fabricated by adopting different VTH adjusted simply by using different contact characteristics between various electrodes and semiconductor. TFTs using Ti/Al electrodes were used in depletion mode (D-mode), and TFTs using ISO electrode or ITO electrode were used as an enhancement mode (E-mode) since TFT using Ti/Al electrodes has more negative VTH than that of oxide electrodes. High voltage gains of inverters have been obtained 12.33 and 11.75 at VDD= 5 V. Furthermore, it was also confirmed that more complicated n-type-based NAND and NOR thin film circuits were implemented by adopting different electrodes, resulting in showing the possibility of most of logic circuits operated like logic tables. This simple fabrication method of thin film logic circuits can open the possibility of the implementation of next generation stacked semiconductor integrated circuit technology.
Reference
IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 66, NO. 2, P957