Subpixel TFT Layout With Stacked Storage Capacitors
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Solution Overview
Problem
In high-resolution display devices, it is challenging to design high-capacity storage capacitors and multiple transistors within the limited area of each subpixel due to the constraints of pixel size, as conventional thin film transistor array substrates cannot differentiate between the characteristics of driving and switching transistors.
Innovation Solution
The display device incorporates multiple storage capacitors formed by overlapping storage electrodes made of different semiconductor materials, along with poly-silicon and oxide semiconductor transistors, to effectively utilize the limited space and enhance storage capacity within each subpixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional thin film transistor array substrates are used with the same semiconductor material for both driving and switching transistors, then manufacturing is simplified, but it is impossible to design different characteristics for driving and switching transistors
Solution Approach 1:
The patent applies local quality by using different semiconductor materials in different regions of the substrate. Specifically, the driving transistor uses a first semiconductor material (e.g., low-temperature polysilicon) while the switching transistor uses a second semiconductor material (e.g., oxide semiconductor). This allows each transistor to be optimized for its specific function: the driving transistor for gradation presentation with small current change amount to voltage change amount, and the switching transistor for fast on-off characteristics with good on/off ratio.
2Measurement precision
If pixel area is reduced to increase resolution, then display resolution is improved, but it becomes difficult to design high-capacity storage capacitor and multiple transistors in each subpixel area
Solution Approach 1:
The patent applies dimensionality change by transitioning from a planar arrangement to a three-dimensional stacked structure. Multiple storage capacitors are formed by stacking storage electrodes and insulation layers vertically within the subpixel area. This allows the storage capacitor capacity to be increased without increasing the horizontal footprint, thereby enabling high-resolution displays with sufficient storage capacity in reduced pixel areas.
3Quantity of substance
If multiple storage capacitors are formed by overlapping storage electrodes, then storage capacity is increased in limited space, but device structure becomes more complex
Solution Approach 1:
The patent applies multi-functionality by designing the stacked structure to serve multiple purposes simultaneously. The same stacked structure of electrodes and insulation layers functions both as storage capacitors and as interlayer insulation for the thin film transistors. For example, the first interlayer insulation layer serves as both insulation for the first transistor gate and as part of the storage capacitor structure. This integrated design increases storage capacity while minimizing additional structural complexity.
Data Source
AI summary
The present disclosure provides a display device comprising: a first thin film transistor including a first semiconductor pattern disposed on a substrate and comprising poly-silicon, and a first gate electrode; a middle layer on the first gate electrode; a second thin film transistor including a second semiconductor pattern disposed on the middle layer and comprising an oxide semiconductor, and a second gate electrode; and a storage capacitor including first to fourth storage electrodes overlapping with each other.