Test System for Thin Film Transistor Parameter Extraction in Active Matrix Backplanes

Abstract

Thin film transistor (TFT) active matrix backplanes are used in large area electronic systems, such as displays and image sensors. With backplanes being fabricated on wearable and flexible substrates, the possibilities of operational faults in backplanes have increased. These faults could either be hard faults, such as line opens or shorts or could be softer faults, such as time dependent variations in the TFT transfer characteristics. Real time diagnosis of these faults require built-in-self-test systems. While many such systems have been demonstrated to diagnose hard faults, an easily realizable system to identify soft faults, such as variations in transistor transconductance remain an open challenge. In this paper, we discuss a system that extracts the transconductance by charging and then discharging the pixel capacitor at various gate voltages for an active matrix liquid crystal display backplane. This permits a plot of the time averaged current versus the gate voltage from which the spatial variation of transconductance can be extracted. The details of the design are discussed and a proof of concept with a 3 × 4 amorphous silicon backplane is demonstrated.

Self‐Healing Thin‐Film Transistor Circuits on Flexible Substrates

“…Inkjet‐printed thin‐film transistors (TFTs) promise tailor‐made circuits on mechanically rigid and flexible substrates for applications such as flexible displays, large area sensors, and wearable electronics. [ 1–7 ] In such applications, the circuit experiences mechanical stress from repeated bending and stretching, thermal strain, electrical stress caused by electrostatic discharge (e.g., from human contact) or electromigration and environmental corrosion due to moisture (e.g., sweat) [ 8–14 ] Thus, the reliability of the interconnect becomes important as open‐circuit failures become more probable. [ 10–13 ]…”

Electric Field Assisted Self-Healing of Open Circuits with Conductive Particle-Insulating Fluid Dispersions: Optimizing Dispersion Concentration

“…Open circuit faults in the interconnects of electronic systems occur due to several mechanisms such as current spikes during electrostatic discharge events, electro-migration, mechanical and thermal stress and environmental or chemical degradation. This problem is more significant in emerging technologies such as flexible and wearable electronic systems where there is a larger possibility for faults to occur during system operation 1,2 .…”

Self-Healing Interconnects for Hybrid Flexible Electronics

“…In any case, with the substrate expected to experience significant bending and stretching, thin-film interconnects are expected to fracture and result in open-circuit faults [17]- [21]. Mechanical stress is not the only cause of open faults in interconnects.…”