TFT Array Panel Capping Layer for Contact Hole Integrity
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Solution Overview
Problem
In the manufacturing process of thin film transistor (TFT) array panels, the difference in materials between insulating layers can lead to the loss of organic insulating material, increasing contact resistance and causing short circuits due to the exposure of electrodes.
Innovation Solution
A capping layer is introduced on the inner lateral surface of the insulating layers, with a design that includes an upper portion connected to the inner portion, which is separated from the electrodes, to prevent material loss and maintain a sufficient thickness, thereby reducing contact resistance and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact holes are formed in the insulating layer between electrodes, then electrical connection between layers is achieved, but the insulating layer covering the TFT is also removed causing material loss and increased contact resistance
Solution Approach 1:
The insulating layer structure is segmented into two distinct parts: the first insulating layer between electrodes (where contact holes are formed) and the second insulating layer covering the TFT (which is protected). This segmentation allows contact holes to be formed in the first layer without removing the protective second layer, thus preventing material loss and maintaining TFT characteristics.
Solution Approach 2:
The first insulating layer acts as an intermediary between the electrode layers and the protective second insulating layer. It provides the necessary pathway for electrical connection through contact holes while the second insulating layer maintains protection over the TFT, mediating between the need for electrical connection and the need for protection.
2Reliability
If the insulating layer covering the TFT becomes thin to allow contact hole formation, then electrical connection is enabled, but the electrode may be exposed causing short circuits
Solution Approach 1:
The protective insulating structure is divided into two layers: the first insulating layer that is removed to form contact holes (enabling electrical connection) and the second insulating layer that remains to cover and protect the TFT electrodes (preventing short circuits). This segmentation resolves the contradiction by allowing thinning/removal only where needed while maintaining protection where required.
Solution Approach 2:
The second insulating layer is deposited beforehand to provide protective coverage over the TFT electrodes. This prior cushioning ensures that even when the first insulating layer is removed to create contact holes, the electrodes remain protected from exposure and short circuiting, as the second layer acts as a protective barrier.
3Ease of manufacture
If organic insulating material is used to cover the TFT, then flexibility and processing are improved, but material loss during contact hole formation causes severe increase in contact resistance
Solution Approach 1:
The organic insulating material is segmented into two functional zones: the first insulating layer between electrodes (where controlled removal creates contact holes) and the second insulating layer covering the TFT (which is preserved). This segmentation prevents loss of the organic material over the TFT while still enabling contact hole formation in the first layer, maintaining both ease of manufacture and preventing material loss.
Solution Approach 2:
The second insulating layer of organic material is deposited preliminarily to cover and protect the TFT before any contact hole formation processes occur. This preliminary action ensures that the organic material is in place for protection before subsequent processing steps that might cause material loss, thereby preventing contact resistance increase while maintaining the processing benefits of organic materials.
Data Source
AI summary
A TFT array panel of a display device includes a first substrate, a first electrode disposed on the first substrate, a first insulating layer including a first hole, the first insulating layer disposed on the first electrode, a second insulating layer disposed on the first insulating layer and including a second hole corresponding to the first hole, and a capping layer including a first inner portion, the capping layer disposed on an inner lateral surface forming the second hole, where an end portion of the first inner portion disposed in the second hole is separated from the first electrode.