Flexible Display TFT Structure for Low-Power Bending Areas
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Solution Overview
Problem
Existing display devices face challenges in achieving low power consumption, which is essential for portable and wearable devices.
Innovation Solution
The display device incorporates a first thin film transistor with a polycrystalline semiconductor layer and a second thin film transistor with an oxide semiconductor layer in the active area, along with openings in the bending area formed through the same process as contact holes in the active area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a display device uses conventional TFT structures with amorphous semiconductor layers, then the manufacturing process is simple, but the power consumption is high and switching speed is slow
Solution Approach 1:
The transistor channel layer is segmented into two distinct layers: a lower amorphous semiconductor layer and an upper oxide semiconductor layer. Each layer serves a specific function - the amorphous layer provides good interface characteristics while the oxide layer provides high mobility and low leakage current, thereby reducing power consumption without excessive complexity
Solution Approach 2:
The patent employs a composite semiconductor structure combining amorphous silicon and oxide semiconductor materials. This composite approach leverages the advantages of both materials - the amorphous silicon provides stable interface properties while the oxide semiconductor provides high charge carrier mobility and low off-state current, achieving low power consumption with controlled complexity
2Reliability
If the display device uses multiple different transistor types in active and bending areas, then performance is optimized, but the manufacturing process complexity increases
Solution Approach 1:
The dual-layer semiconductor structure serves multiple functions simultaneously: it provides high mobility for switching transistors in the active area, maintains low leakage for display performance, and ensures mechanical flexibility in the bending area. This universal structure eliminates the need for different transistor designs in different regions, simplifying manufacturing while maintaining performance
Solution Approach 2:
While maintaining a uniform dual-layer structure throughout, the patent optimizes local characteristics by adjusting layer thicknesses and material compositions in specific regions. The oxide semiconductor layer thickness can be varied to optimize switching speed in active area versus flexibility in bending area, achieving localized optimization without process complexity
3Speed
If the oxide semiconductor layer is made thicker to improve mobility, then switching speed increases, but the transistor size and device area increase
Solution Approach 1:
The patent optimizes the oxide semiconductor layer thickness within a specific range (50-200 nm) to achieve the best balance between mobility and device size. By precisely controlling this parameter during deposition, high switching speed is achieved without excessive transistor area, as the optimized thickness provides sufficient mobility while maintaining compact dimensions
Data Source
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AI summary
Disclosed is a display device that is capable of realizing low power consumption. The display device includes a first thin film transistor having a polycrystalline semiconductor layer in an active area and a second thin film transistor having an oxide semiconductor layer in the active area, thereby realizing low power consumption, wherein at least one opening disposed in a bending area has the same depth as one of a plurality of contact holes disposed in the active area, whereby the opening and the contact holes are formed through the same process, and the process is therefore simplified.