Technology Computer-Aided Design-Based Simulation Program with Integrated Circuit Emphasis Model for Back-Channel-Etched Thin-Film Transistors with Floating Metal Components.

We report thin-film transistors (TFTs) with floating metal using a back-channel-etched (BCE) process. Since the BCE process reduces the active mask step compared to other processes, it has attracted attention as a back-plane process that could be used for mass production. To realize the long channel in the BCE process, a floating metal is required; this acts as a bridge in the middle of the channel. We used TCAD (Technology computer-aided design) simulations (Atlas 3D) to predict the characteristics of a-Si TFTs with various active layer thicknesses and numbers of floating metal components; simulation results were compared with real measurements. We explain why TFTs do not scale ideally when floating metals are used; this is related to the resistance and thickness of the active channel. If a thick and highly resistive active channel is used, a larger number of floating metals will require greater correction for ideal scaling. Additionally, considering the capacitance between the source metal and channel, the channel influence under the floating metal should be about 89%. We also suggest a new SPICE (Simulation Program with Integrated Circuit Emphasis) model for TFTs with floating metal based on TCAD simulations.