Overlapping Thin-Film Transistor Substrate for OLED Area Reduction
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Solution Overview
Problem
Thin-film transistor substrates in OLED devices face challenges with semiconductor layers, as amorphous semiconductors have low electron mobility, polycrystalline semiconductors require compensation circuits due to non-uniform threshold voltage, and oxide semiconductors have lower mobility than polycrystalline semiconductors and lower threshold voltage.
Innovation Solution
A thin-film transistor substrate design featuring a first thin-film transistor with a polycrystalline semiconductor layer and a second thin-film transistor with an oxide semiconductor layer, where the second transistor's semiconductor layer overlaps the first, allowing for electrical connection through a contact hole, reducing the area occupied by transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If polycrystalline semiconductor is used for the semiconductor layer, then electron mobility is improved, but threshold voltage uniformity deteriorates
Solution Approach 1:
The patent applies local quality by using different semiconductor materials in different regions: polycrystalline semiconductor for the first transistor (prioritizing electron mobility) and oxide semiconductor for the second transistor (prioritizing threshold voltage uniformity). This allows each transistor to be optimized for its specific function while maintaining overall device performance.
2Reliability
If oxide semiconductor is used for the semiconductor layer, then threshold voltage is improved, but electron mobility deteriorates
Solution Approach 1:
The patent applies local quality by using different semiconductor materials in different regions: polycrystalline semiconductor for the first transistor (prioritizing electron mobility) and oxide semiconductor for the second transistor (prioritizing threshold voltage uniformity). This allows each transistor to be optimized for its specific function while maintaining overall device performance.
3Ease of manufacture
If amorphous semiconductor is used for the semiconductor layer, then manufacturing is simplified, but electron mobility deteriorates
Solution Approach 1:
The patent applies parameter changes by transitioning from amorphous semiconductor to polycrystalline semiconductor for the first transistor, significantly improving electron mobility. The use of oxide semiconductor for the second transistor provides a balance between manufacturability and electrical characteristics, allowing the device to achieve high performance while remaining manufacturable.
4Area of stationary object
If transistors are arranged in overlapping configuration, then area is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies dimensionality change by transitioning from a planar transistor arrangement to a three-dimensional overlapping configuration. The second transistor is positioned above the first transistor in the vertical dimension, allowing both transistors to share the same footprint area on the substrate. This vertical stacking approach significantly reduces the overall device area while the manufacturing process remains manageable through sequential formation steps.
Data Source
AI summary
A thin-film transistor substrate may include a first thin-film transistor and a second thin-film transistor which are disposed on a substrate. The first thin-film transistor may include a first semiconductor layer, a first gate electrode, and a first electrode. The second thin-film transistor may include a second semiconductor layer disposed on the first semiconductor layer and overlapping at least a portion of the first semiconductor layer, a second gate electrode, and a second electrode electrically connected to the first electrode. The second electrode may overlap the first electrode.