Active Matrix Substrate Drain Electrode Protection
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Solution Overview
Problem
In active matrix substrates with a common electrode lower layer structure, the pixel contact portion's design can lead to damage of the drain electrode during the manufacturing process, resulting in a decrease in pixel aperture ratio and auxiliary capacity.
Innovation Solution
The active matrix substrate incorporates a connection electrode formed using the same conductive film as the touch wiring line, which covers the exposed portion of the drain electrode in the contact hole, allowing the pixel electrode to be connected to the drain electrode without direct exposure to etching solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pixel contact portion is formed with the drain electrode exposed in the contact hole, then the pixel electrode can be connected to the drain electrode, but the exposed drain electrode surface is damaged by etching solution during manufacturing
Solution Approach 1:
A protective film is introduced as an intermediary layer between the etching solution and the drain electrode surface. This protective film allows the etching process to proceed while preventing direct contact between the etching solution and the drain electrode, thus maintaining surface integrity while achieving proper electrical connection
Solution Approach 2:
The protective film is formed on the drain electrode surface before the etching process. This preliminary protective action ensures that when subsequent etching steps are performed, the drain electrode surface remains undamaged, solving the problem of surface degradation during manufacturing
2Reliability
If the pixel contact portion area is increased to ensure proper connection, then connection reliability improves, but the pixel aperture ratio decreases
Solution Approach 1:
The protective film is applied locally only to the drain electrode surface in the contact hole region, rather than across the entire pixel area. This localized approach provides necessary protection and connection reliability while minimizing impact on the overall pixel aperture ratio
3Device complexity
If the common electrode is positioned on the substrate side of the pixel electrode, then the structure is simplified, but the drain electrode becomes vulnerable to etching damage
Solution Approach 1:
The protective film serves as an intermediary barrier that enables the simplified common electrode lower layer structure to be implemented without suffering from etching damage. This mediator allows the vulnerable drain electrode to coexist with the simplified structure while remaining protected during manufacturing
Data Source
AI summary
An active matrix substrate includes a plurality of thin film transistors including an oxide semiconductor layer, an interlayer insulating layer, a plurality of pixel electrodes arranged above the interlayer insulating layer, a common electrode arranged between the pixel electrode and the interlayer insulating layer and also configured to function as a touch sensor electrode, a first dielectric layer arranged between the interlayer insulating layer and the common electrode, a second dielectric layer arranged between the common electrode and the pixel electrode, a plurality of touch wiring lines arranged between the interlayer insulating layer and the common electrode and formed of a third conductive film, and a plurality of pixel contact portions, in which each of the plurality of pixel contact portions includes a drain electrode of the thin film transistor, a connection electrode formed of the third conductive film and electrically connected to the drain electrode in a lower opening formed in the interlayer insulating layer, and a pixel electrode electrically connected to the connection electrode in an upper opening formed in the first dielectric layer and the second dielectric layer.