Oxide Thin Film Transistor Layout for Light-Stable Low-Capacitance Pixels
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Solution Overview
Problem
Conventional thin film transistors using oxide semiconductors like ZnO, IGZO, and ZTO face issues with light-induced photocurrent generation, shifting the threshold voltage and affecting electrical performance and reliability, and large gate areas lead to low aperture ratios and increased parasitic capacitance, resulting in high power consumption.
Innovation Solution
A thin film transistor design with a metal oxide active layer containing a doped element with high dissociation energy from oxygen, where the gate area is minimized to reduce parasitic capacitance and improve light stability, featuring a source, drain, and middle portion with specific overlapping regions and connections to signal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate area is increased to improve light shielding and electrical performance, then the reliability improves, but the aperture ratio decreases
Solution Approach 1:
The patent changes the material parameter of the active layer from conventional amorphous silicon to metal oxide semiconductor with high dissociation energy (>500Kj/mol), which fundamentally alters the light interaction mechanism. This material parameter change enables the gate to provide sufficient electrical performance stability without requiring increased gate area for light shielding, thus resolving the contradiction between reliability and aperture ratio
Solution Approach 2:
The patent employs composite material structure by doping metal oxide semiconductor with specific elements (rare earth elements, tungsten, or tantalum) that have dissociation energy greater than 500Kj/mol. This composite approach enhances the material's resistance to light-induced photocurrent shifts while maintaining optical transparency, allowing smaller gate area while preserving electrical performance stability
2Productivity
If oxide semiconductor is used to improve carrier mobility, then the productivity improves, but the reliability deteriorates due to photocurrent shifts
Solution Approach 1:
The patent specifically selects metal oxide semiconductor materials with dissociation energy greater than 500Kj/mol, which is a critical parameter change that differentiates them from conventional oxides. This high dissociation energy parameter prevents light-induced oxygen vacancy formation and subsequent photocurrent shifts, thereby maintaining both high carrier mobility and electrical performance stability
Solution Approach 2:
The patent applies local quality enhancement by introducing doped elements (rare earth elements, tungsten, or tantalum) into specific regions of the metal oxide semiconductor active layer. This localized doping creates regions with enhanced stability against photocurrent shifts while preserving the overall high carrier mobility of the oxide semiconductor material
3Area of moving object
If the gate area is minimized to improve aperture ratio, then the area improves, but the parasitic capacitance reduces affecting electrical performance
Solution Approach 1:
The patent changes the material parameter of the active layer to metal oxide semiconductor with high dissociation energy, which fundamentally alters the electrical characteristics. This material parameter change reduces the required gate area for achieving stable electrical performance, allowing aperture ratio improvement without sacrificing electrical performance due to parasitic capacitance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances the stability of the thin film transistor under light exposure, improves the aperture ratio, and reduces power consumption by minimizing the gate area and parasitic capacitance, ensuring reliable electrical performance.
Implementation Method 1
a material of the middle portion includes a metal oxide containing a doped element, and a dissociation energy of the doped element from an oxygen element is greater than 500 Kj/mol
Data Source
AI summary
Provided are a thin film transistor, a display substrate and a display device, the thin film transistor includes: a gate on a base substrate; an active layer between the gate and the base substrate, the active layer includes a source contact portion, a drain contact portion and a middle portion therebetween, orthographic projections of the middle portion and the gate on the base substrate overlaps to form a first overlapping region, a material of the middle portion includes a metal oxide containing a doped element, a dissociation energy of the doped element from an oxygen element is greater than 500 Kj/mol; a source connected to the source contact portion and a drain connected to the drain contact portion, a ratio of an area of the orthographic projection of the gate on the base substrate to an area of the first overlapping region is less than or equal to 3.