TFT Substrate with Asymmetric Semiconductor Layer for Aperture Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Amorphous silicon TFTs in LCDs suffer from leakage current when exposed to backlight, leading to flickering and afterimages due to their full island structure, which also results in a low aperture ratio and increased RC delay.
Innovation Solution
A TFT substrate design where the semiconductor layer under the drain electrode is within the gate electrode area, and the semiconductor layer under the source electrode extends outward from the gate electrode, with an ohmic contact layer between the semiconductor layer and data wiring, reducing exposure to backlight and minimizing overlap areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a full island structure is used to prevent amorphous silicon from being exposed to backlight, then afterimages are reduced, but the aperture ratio decreases
Solution Approach 1:
The patent applies local quality by differentiating the coverage of the gate electrode over the semiconductor layer in different regions. Specifically, the gate electrode covers the semiconductor layer in the drain region to prevent light exposure and afterimages, while leaving the semiconductor layer exposed in the source region to maintain high aperture ratio. This selective coverage strategy resolves the contradiction by applying protection only where necessary.
2Reliability
If the gate electrode area is increased to cover the semiconductor layer fully, then leakage current is reduced, but RC delay increases
Solution Approach 1:
The patent implements local quality by applying gate electrode coverage selectively in the drain region where leakage current prevention is critical, while minimizing coverage in the source region to reduce capacitance and RC delay. This localized approach maintains reliability where needed without sacrificing speed performance.
Solution Approach 2:
The patent segments the gate electrode coverage into different functional regions: a first gate electrode covering the semiconductor layer in the drain region for leakage prevention, and a second gate electrode (or lack thereof) in the source region for maintaining low RC delay. This segmentation allows independent optimization of reliability and speed in different parts of the device.
Data Source
AI summary
Disclosed is a TFT substrate for a display apparatus comprising a gate wiring including a gate electrode, a data wiring including a data line, a source electrode connected to the data line, and a drain electrode connected to a pixel electrode, and a semiconductor layer disposed between the gate wiring and the data wiring, wherein the semiconductor layer under the drain electrode is disposed within an area overlapping the gate electrode and the semiconductor layer under the source electrode extends outward to an area not overlapping the gate electrode. Advantageously, the present disclosure provides a TFT substrate for a display apparatus having a high aperture ratio and causing less afterimaging, and a manufacturing method of the same.