Thin Film Transistor Light-Protection Layer for Leakage Current Reduction
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Solution Overview
Problem
Oxide semiconductor thin film transistors (TFTs) suffer from poor light stability due to oxygen vacancy defects, which are not effectively shielded by conventional organic light-shielding materials when light is incident from the bottom or top, leading to significant leakage currents.
Innovation Solution
A thin film transistor design incorporating a light-protection layer made of metal oxides, such as zinc-based nitrogen oxide, positioned above or below the active layer to absorb light of specific wavelengths, thereby reducing the impact of light irradiation on the active layer and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic light-shielding materials (resin, BM, CF) are used to shield TFT from light, then light stability of TFT is improved when light irradiates from the top, but the shielding effect is lost when light is incident from the bottom through the substrate
Solution Approach 1:
The patent introduces a light-protection layer positioned between the substrate and the active layer, changing the spatial arrangement from top-only shielding to bottom-up shielding. This dimensional change in light blocking approach ensures that light incident from the bottom through the substrate is intercepted before reaching the channel region, while maintaining compatibility with top-gate and bottom-gate TFT structures
Solution Approach 2:
The light-protection layer acts as an intermediary component between the substrate and the active layer. This intermediate layer specifically targets and absorbs light incident from the bottom direction, complementing the existing top-down light shielding approach. The mediator layer has specific optical properties (band gap 1.1-2.3 eV, transmissivity <70%) that enable selective light absorption without interfering with other TFT functions
2Reliability
If oxide semiconductor materials with oxygen vacancies are used in TFT, then the material properties and conductivity are improved, but light irradiation excites electrons in oxygen vacancies causing large leakage current and poor light stability
Solution Approach 1:
The light-protection layer is positioned to preemptively block light from reaching the active layer before light-induced electron excitation can occur. By absorbing light with wavelengths corresponding to the oxygen vacancy energy levels (band gap 1.1-2.3 eV) in the oxide semiconductor material, the layer prevents the harmful photo-excitation process before it starts, thereby reducing leakage current and improving light stability
3Reliability
If a light-protection layer is added to shield TFT from light, then light stability is improved, but the device structure and manufacturing complexity increase
Solution Approach 1:
The light-protection layer is designed with specific parameter ranges: band gap of 1.1-2.3 eV and transmissivity less than 70%. These parameter specifications ensure optimal light absorption characteristics while maintaining compatibility with existing TFT manufacturing processes. The layer thickness and material composition are optimized to achieve the required optical properties without adding excessive structural complexity
Solution Approach 2:
The light-protection layer is designed to be universally applicable to both top-gate and bottom-gate TFT structures. The same layer configuration and material properties provide effective light shielding in both gate configurations, eliminating the need for structure-specific modifications and reducing overall device complexity
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 light-protection layer effectively absorbs light, preventing oxygen vacancy excitation and reducing leakage currents, thereby ensuring improved light stability and performance of the TFT, even when light is incident from various angles.
Implementation Method 1
the light-protection layer is configured to absorb light having a predetermined wavelength
Data Source
AI summary
A thin film transistor comprises an active layer; a light-protection layer disposed above the active layer and/or disposed beneath the active layer, the light-protection layer being configured to absorb light having a predetermined wavelength. By providing a light-protection layer above the active layer, light incident onto the channel region from top of the thin film transistor can be absorbed, while by providing a light-protection layer under the active layer, light incident onto the channel region from bottom of the thin film transistor can be absorbed, thereby effectively avoiding influence of light on the active layer of the channel region and ensuring a relatively strong light stability of the driving transistor in the thin film transistor. A method for manufacturing a thin film transistor and an array substrate comprising the thin film transistor as well as an array substrate and a display device comprising the thin film transistor are further provided.