Thin Film Transistor Array Substrate with Overlapping Capacitor
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Solution Overview
Problem
The production of OLED displays using low temperature poly silicon (LTPS) technology is complex and costly, with large off-current leading to image sticking and reduced aperture ratio due to large gate length and small gate width in thin film transistors, necessitating a simpler and more cost-effective manufacturing process for thin film transistor array substrates.
Innovation Solution
A thin film transistor array substrate with a top gate structure comprising silicon and oxide semiconductor transistors, along with an overlapping capacitor arrangement, utilizing a polysilicon layer, semiconductor oxide layer, and a floating gate to reduce the number of photoresist masks required, thereby simplifying the manufacturing process and increasing aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTPS technology is used to manufacture CMOS circuits, then carrier mobility is improved, but the production process becomes complex and costly with large off-current
Solution Approach 1:
The patent divides the semiconductor layer into two distinct segments: a first semiconductor layer (LTPS) for the driving transistor requiring high carrier mobility, and a second semiconductor layer (amorphous silicon) for the switching transistor where low off-current is critical. This segmentation allows each layer to be optimized independently, reducing overall device complexity while maintaining high reliability.
2Reliability
If LTPS technology is used, then carrier mobility is improved, but off-current increases leading to image sticking
Solution Approach 1:
The patent applies local quality by using different semiconductor materials in different regions of the display panel. The LTPS material is used locally in the driving transistor where high carrier mobility is needed for OLED driving, while amorphous silicon is used locally in the switching transistor where low off-current is critical to prevent image sticking. This localized material selection optimizes performance for each specific function.
3Object-generated harmful factors
If gate length is increased to reduce off-current, then off-current is reduced, but aperture ratio decreases
Solution Approach 1:
The patent changes the material parameter of the semiconductor layer to achieve the desired electrical characteristics without altering the geometric parameters. By using amorphous silicon with inherently lower carrier mobility in the switching transistor, the patent achieves low off-current with a smaller gate length, thereby maintaining a larger aperture ratio compared to using LTPS throughout.
4Manufacturing precision
If photoresist mask processes are increased to achieve precise transistor patterns, then manufacturing precision is improved, but production complexity and cost increase
Solution Approach 1:
The patent employs a universal amorphous silicon layer that serves multiple functions: it acts as the semiconductor layer for switching transistors and can be selectively doped to form source and drain regions. This multi-functional approach reduces the need for separate photoresist mask processes for different transistor types, simplifying the manufacturing process while maintaining precision.
Data Source
AI summary
The present disclosure discloses a thin film transistor array substrate and a liquid crystal panel. The thin film transistor array substrate comprises a substrate, a silicon thin film transistor formed on the substrate, an oxide semiconductor transistor, and a capacitor. Wherein, the silicon thin film transistor and the oxide semiconductor transistor have a top gate structure, which is compatible with the manufacturing process of the silicon thin film transistor and the oxide semiconductor transistor, so that it can reduce the use frequency of the photoresist mask, and then reduce the production cost of the thin film transistor array substrate. In addition, the capacitor and the silicon thin film transistor or the capacitor and the oxide semiconductor transistor are overlapping arrangement, which can greatly increase the aperture ratio of the bottom emitting OLED.