LTPS TFT Active Layer Carrier Concentration Modulation
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Solution Overview
Problem
Organic light emitting display panels with low temperature poly silicon (LTPS) TFTs experience high off-current and increased power consumption due to the formation of hump channels, leading to transistor deterioration and reduced reliability.
Innovation Solution
The implementation of a passivation layer on an active layer with distinct carrier concentrations in taper parts and channel parts, reducing the occurrence of free carriers and preventing the shift in gate-source voltage, thereby minimizing off-current and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional LTPS TFT is manufactured with inclined planes on both sides of the active layer, then the manufacturing process is simple, but a hump channel forms causing high off-current and increased power consumption
Solution Approach 1:
The patent applies local quality by creating a multi-region active layer structure where the channel part has a first carrier concentration and the taper parts have a second carrier concentration (higher than the first). This differential doping creates localized electrical characteristics that prevent hump channel formation at the taper regions while maintaining proper current flow in the channel, thereby reducing off-current without complicating the overall manufacturing process.
2Temperature
If the LTPS TFT is operated with the hump channel structure, then the device can be manufactured at low temperature, but the gate-source voltage shifts negatively and transistor deterioration accelerates
Solution Approach 1:
The patent employs parameter changes by modifying the carrier concentration distribution within the active layer. The channel part maintains a lower carrier concentration while the taper parts have a higher carrier concentration. This parameter variation prevents the formation of hump channels that would otherwise cause negative gate-source voltage shifts, thereby extending transistor operational lifetime while preserving the low-temperature manufacturing advantage of LTPS TFTs.
3Ease of manufacture
If the conventional active layer structure is used, then the process cost remains low, but power consumption increases due to high off-current
Solution Approach 1:
The patent reduces power consumption through local quality modification by implementing differential carrier concentration in the active layer. The taper parts with higher carrier concentration prevent hump channel formation, which eliminates the source of high off-current. This localized structural optimization achieves significant power savings while maintaining compatibility with existing low-cost LTPS manufacturing processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces off-current and power consumption, enhances the reliability of the organic light emitting display panel, and prevents transistor deterioration without increasing process costs.
Implementation Method 1
a carrier concentration of each of the first taper part and the second taper part is different from those of the channel part, the first electrode connection part and the second electrode connection part
Data Source
AI summary
A display panel and a method for manufacturing the display panel are discussed. The display panel includes a substrate; an active layer on the substrate; and a passivation layer on the active layer, wherein the active layer includes a channel part, a first electrode connection part and a second electrode connection part on opposite sides of the channel part in a first direction, and a first taper part and a second taper part on opposite sides of the channel part in a second direction crossing the first direction, and wherein a carrier concentration of each of the first taper part and the second taper part is different from those of the channel part, the first electrode connection part and the second electrode connection part.