Shield Electrode Reduces Leakage in TFT Displays
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Solution Overview
Problem
In liquid crystal display devices with thin-film transistors, the semiconductor layer extending beyond the gate electrode leads to light leakage current, resulting in high OFF-leakage current and potential residual images.
Innovation Solution
A shield is provided on the protective insulating film, independent of the pixel electrode, to suppress the formation of a backgate channel and reduce OFF-leakage current, while being formed together with the pixel electrode to simplify fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the semiconductor layer extends beyond the gate electrode to simplify fabrication, then the manufacturing process is easier, but light leakage current increases causing high OFF-leakage current and residual images
Solution Approach 1:
A shield electrode is introduced as an intermediary component between the pixel electrode and the semiconductor layer. This shield electrode is connected to the gate electrode, creating an electric field that prevents backgate channel formation in the semiconductor layer region that extends beyond the gate electrode. The shield acts as a mediator that blocks the harmful electric field interaction while allowing the semiconductor layer to extend for fabrication simplicity.
2Object-generated harmful factors
If the semiconductor layer is positioned within the gate electrode range to suppress light leakage current, then OFF-leakage current is reduced, but the fabrication process becomes more complex
Solution Approach 1:
The shield electrode serves as a mediator that allows the semiconductor layer to extend beyond the gate electrode without causing harmful backgate channel effects. By connecting the shield to the gate electrode, it creates a controlled electric field environment that suppresses OFF-leakage current while permitting the simpler fabrication process of having the semiconductor layer extend beyond the gate electrode boundaries.
3Object-generated harmful factors
If a shield is added to suppress backgate channel formation, then OFF-leakage current is reduced, but device structure becomes more complex
Solution Approach 1:
The shield electrode is designed to serve multiple functions: it suppresses backgate channel formation in the semiconductor layer, controls the electric field distribution, and can be integrated with existing gate electrode structures. By making the shield electrode multi-functional, the added structural complexity is justified by the multiple benefits it provides in solving the light leakage current problem.
Solution Approach 2:
The shield electrode is electrically connected to the gate electrode, merging their functions to some extent. This connection allows the shield to utilize the gate electrode's potential while independently performing the backgate channel suppression function, thereby reducing the overall system complexity compared to having completely separate structures.
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
The shield effectively reduces OFF-leakage current and prevents residual images by isolating the channel-formation region from charge effects, improving display performance.
Implementation Method 1
a shield provided on the protective insulating film, the shield not being electrically connected to the pixel electrode
Data Source
AI summary
The instant application describes a display device that includes a substrate; a gate electrode provided on the substrate; a gate insulating film provided on the gate electrode; a semiconductor layer provided on the gate insulating film; a source electrode and a drain electrode provided on the semiconductor layer; a protective insulating film provided on the source electrode and the drain electrode; a pixel electrode provided on the protective insulating film, and connected to one of the source electrode and the drain electrode through a contact hole formed through the protective insulating film; and a shield provided on the protective insulating film, the shield not being electrically connected to the pixel electrode.