U-Type TFT With Protruding Electrodes For LCD Gate Driving Stability
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Solution Overview
Problem
The active layers of thin-film transistors (TFTs) in gate driving modules of liquid crystal displays (LCDs) are prone to instability due to differences in thickness, leading to malfunctions as they are more easily removed during etching, affecting the gate-drain to gate-source capacitance ratio and channel length, which are crucial for proper operation.
Innovation Solution
The implementation of U-type TFTs with a gate-drain to gate-source capacitance ratio of 1:1 and a long channel length in the peripheral region of LCD panels, featuring source and drain electrodes with protruding portions or floating electrodes, ensures stable channel formation and resistance, preventing excessive removal during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If U-type TFTs are used in gate driving modules, then manufacturing is easier, but active layers are more easily removed during etching causing instability
Solution Approach 1:
The patent applies different thicknesses of photosensitive layer to different regions: a first thickness in the display region and a second thickness (greater than the first) in the gate driving module region. This local differentiation ensures that the active layer in the gate driving module region is sufficiently thick to resist etching while maintaining the U-type TFT structure's manufacturing advantages.
Solution Approach 2:
The patent changes the thickness parameter of the photosensitive layer based on location. By increasing the photosensitive layer thickness in the gate driving module region, the active layer formed therein has greater thickness, which prevents excessive removal during etching while preserving the ease of U-type TFT fabrication.
2Reliability
If photosensitive layer thickness is increased to prevent active layer removal, then etching stability improves, but capacitance ratio and channel length control becomes difficult
Solution Approach 1:
The patent implements local quality by applying different photosensitive layer thicknesses to different functional regions. The gate driving module region receives a thicker photosensitive layer for etching stability, while the display region maintains its original thickness for precise capacitance control. This spatial differentiation resolves the conflict between etching stability and manufacturing precision.
Solution Approach 2:
The patent segments the photosensitive layer thickness into two distinct regions: a first photosensitive layer in the display region and a second photosensitive layer in the gate driving module region. This segmentation allows independent optimization of each region's properties without compromising the other.
3Reliability
If channel length is increased to secure sufficient resistance, then resistance is adequate, but TFT patterning uniformity decreases
Solution Approach 1:
The patent applies local quality by configuring TFTs in the gate driving module region with longer channel lengths compared to those in the display region. This localized adjustment ensures sufficient resistance in the gate driving module without compromising the patterning uniformity required in the display region.
Data Source
AI summary
A thin-film transistor (TFT) is provided. The TFT includes a gate electrode; a dielectric layer and an active layer which are formed on the gate electrode; and source and drain electrodes which are formed on the active layer, each of the source and drain electrodes including a plurality of protruding portions and an empty space between each protruding portion, wherein the source and drain electrodes are spaced apart from each other and engage with each other, and further wherein the gate and source electrodes overlap each other and the gate and drain electrodes overlap each other.