Multi-gate TFT Light-shielding Layers Reduce Photo Leakage
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Solution Overview
Problem
Active-matrix flat panel displays using thin film transistor (TFT) devices suffer from photo leakage current due to light impinging on the active layer, which degrades image quality by generating electron-hole pairs, especially when the TFT device is in the OFF state.
Innovation Solution
A multi-gate TFT device with a substrate and active layer configuration that includes first and second source/drain regions, channel regions, and channel connection regions, along with first and second gate structures, and strategically positioned light-shielding layers between the substrate and active layer to shield the lightly doped regions and channel areas from light, reducing photo leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light-shielding layers are added to reduce photo leakage current, then image quality improves, but device complexity increases
Solution Approach 1:
The light-shielding layer is segmented into multiple discrete layers positioned at different locations beneath the active layer. Each light-shielding layer corresponds to specific source/drain regions and channel areas, providing targeted shielding where photo leakage current is most problematic while avoiding unnecessary complexity in regions where it is less critical.
Solution Approach 2:
Light-shielding layers are strategically positioned only in regions where photo leakage current generation is most severe, specifically beneath source/drain regions and channel areas. This localised approach provides effective shielding precisely where needed to improve image quality, while avoiding the addition of complexity across the entire device structure.
2Object-generated harmful factors
If multiple light-shielding layers are positioned under source/drain regions and channel areas, then photo leakage current is reduced, but manufacturing complexity increases
Solution Approach 1:
Multiple light-shielding layers are combined into a unified multi-gate TFT device structure, where all layers are integrated during the same manufacturing process sequence. The light-shielding layers are formed alongside other device components using coordinated deposition and patterning steps, which reduces overall manufacturing complexity compared to adding them as separate post-processing layers.
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 solution effectively reduces photo leakage current and mitigates threshold voltage shifts, ensuring consistent image quality across varying drain-source voltages, thereby preventing abnormal display issues in active-matrix flat panel displays.
Implementation Method 1
A first light-shielding layer and a second light-shielding layer are disposed between the substrate and the active layer, wherein the first light-shielding layer corresponds to the first lightly doped region and laterally extends under at least a portion of the first channel region, and the second light-shielding layer corresponds to the second lightly doped region and laterally extends under at least a portion of the second channel region
Data Source
AI summary
A system for displaying images includes a multi-gate thin film transistor (TFT) device including an active layer, first and second gate structures, and first and second light-shielding layers. The active layer is disposed on a substrate in a pixel region. The first and second gate structures are disposed on the active layer. The first and second light-shielding layers are disposed between the substrate and the active layer. The active layer includes first and second source/drain regions and first and second channel regions. The first light-shielding layer corresponds to a first lightly doped region and laterally extends under at least a portion of the first channel region. The second light-shielding layer corresponds to the second lightly doped region and laterally extends under at least a portion of the second channel region.