Stacked TFT Pixel Structure for Higher Aperture Ratio Displays
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Solution Overview
Problem
As the resolution of display apparatuses and the number of thin film transistors (TFTs) connected to a single display device increase, the pixel aperture ratio decreases, leading to inefficiencies in display performance.
Innovation Solution
A display apparatus is designed with a first thin film transistor and a second thin film transistor on a substrate, where the second transistor overlaps the first, with a conductive layer applied with a direct current voltage, and a planarization layer to optimize the structure and improve aperture ratio, including specific layer configurations and buffer layers to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of display apparatuses and the number of TFTs connected to a single display device are increased, then the display resolution is improved, but the pixel aperture ratio decreases
Solution Approach 1:
The patent transitions from a planar arrangement of TFTs to a three-dimensional stacked configuration where a second TFT is formed on top of a first TFT. This vertical stacking enables multiple TFTs to occupy the same footprint area, thereby increasing the number of TFTs connected to a single display device without reducing the pixel aperture ratio, as the additional TFTs are positioned in the vertical dimension rather than competing for horizontal space.
Solution Approach 2:
The patent implements a nested structure where the second TFT is positioned on top of and overlaps with the first TFT. The second TFT's active layer is formed on the first TFT's gate electrode, creating a hierarchical arrangement where smaller components are integrated within or upon larger ones. This nesting allows dense integration of multiple TFTs within the same pixel area, improving resolution while maintaining aperture ratio.
2Area of stationary object
If a second thin film transistor is added to overlap the first thin film transistor, then the aperture ratio is improved, but the device complexity increases
Solution Approach 1:
The patent divides the TFT structure into distinct segments: a first TFT with its own active layer, gate electrode, and source/drain electrodes, and a second TFT with its own active layer formed on top. This segmentation allows each TFT to be independently designed and optimized while maintaining their overlapping relationship. The planarization layer further segments the structure by providing a flat interface between the two TFTs, simplifying the manufacturing process despite the increased vertical complexity.
Solution Approach 2:
By moving to a three-dimensional stacked architecture, the patent resolves the complexity issue by organizing multiple TFTs in the vertical dimension rather than spreading them horizontally. This vertical arrangement reduces the lateral space required and allows for more efficient use of the pixel area, thereby improving the aperture ratio without proportionally increasing the lateral device footprint.
3Manufacturing precision
If a planarization layer with multiple insulating layers is introduced, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The planarization layer is strategically positioned only where needed - specifically on top of the first TFT's gate electrode and source/drain electrodes, but not necessarily across the entire substrate. This localized application provides surface flatness improvement precisely where the second TFT needs a stable foundation, while avoiding unnecessary complexity in other regions. The first and second insulating layers are configured to provide the required planarization without adding excessive structural complexity.
Data Source
AI summary
A display apparatus including a first thin film transistor including a first active layer, and a second thin film transistor disposed on the first thin film transistor and including a second active layer, in which a material of the first active layer is different from a material of the second active layer, and a channel area of the second active layer overlaps a channel area of the first active layer.