Thin-Film Transistor Gate Structure for Threshold Voltage Stability
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Solution Overview
Problem
In the fabrication of display panels using large-sized mother substrates, performance deviations in thin film transistors lead to reliability issues, such as significant changes in threshold voltage over time.
Innovation Solution
The implementation of a display device with a thin film transistor featuring a gate electrode with a thickness step profile, where a second part with reduced thickness and higher light transmittance overlaps the channel portion, helping to resolve electron traps and stabilize the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform thickness gate electrode is used, then the manufacturing process is simple, but performance deviations occur and reliability deteriorates due to electron traps in the channel portion
Solution Approach 1:
The gate electrode is designed with different thicknesses in different regions: a first thickness in the channel portion and a second thickness in non-channel portions. This local quality variation allows the channel region to have optimized electrical characteristics while maintaining overall device functionality, directly resolving the reliability issue caused by electron traps.
Solution Approach 2:
The gate electrode is segmented into multiple regions with different thicknesses - the first region (channel portion) and second region (non-channel portions). This segmentation enables independent optimization of each region's properties, allowing the channel region to be specifically engineered for reduced electron trap effects.
2Reliability
If the gate electrode thickness is increased to improve electrical performance, then transistor control is enhanced, but light transmittance decreases and performance deviations worsen
Solution Approach 1:
The gate electrode implements local quality by having different thicknesses in different regions. The channel portion has a first thickness optimized for electrical control, while non-channel portions have a second thickness that maintains adequate light transmittance, thus avoiding the trade-off between electrical performance and optical properties.
Solution Approach 2:
The solution moves from a uniform one-dimensional thickness parameter to a two-dimensional thickness distribution across the gate electrode area. This dimensional change allows simultaneous optimization of electrical performance (where needed) and optical properties (where needed) by varying thickness in the planar dimension rather than requiring a compromise uniform thickness.
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 configuration minimizes performance deviations and maintains reliability by resolving electron traps through light transmission, thereby preventing significant changes in threshold voltage over time.
Implementation Method 1
a second part having a thickness smaller than a thickness of the first part and overlapping the channel portion of the active layer, and a light transmittance of the second part is greater than a light transmittance of the first part
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A~4B
AI summary
A thin film transistor, a mother panel comprising the thin film transistor and a display device are provided. The thin film transistor comprises an active layer having a channel portion, and a gate electrode that overlaps the channel portion of the active layer, wherein the gate electrode includes a first part that at least partially overlaps the channel portion, and a second part having a thickness smaller than that of the first part, at least partially overlapping the channel portion, and light transmittance of the second part is greater than that of the first part.