Flat Layer Between Metal Layers for Narrow Bezel Fanout
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Solution Overview
Problem
Existing display technologies face challenges in reducing the fanout pitch of metal wirings in the fanout region, which limits the achievement of narrow bezels due to non-uniformity in the second metal layer caused by unflat insulating layers, affecting fabrication accuracy and line width/spacing consistency.
Innovation Solution
A display substrate design with a flat layer between the first and second metal layers, where the flat layer's surface in the fanout region has a controlled maximum and minimum distance from the horizontal plane, ensuring uniformity and allowing for identical line widths and spacings between first and second metal wirings, thereby improving fabrication accuracy and reducing fanout pitch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a double-layer metal wiring method is used to reduce the fanout region width, then the bezel width is reduced, but the manufacturing precision deteriorates due to non-uniform photoresist thickness caused by unflat insulating layers
Solution Approach 1:
A flat layer is formed on the first insulating layer before forming the second metal layer. This preliminary action creates a flat surface that ensures uniform photoresist thickness when coating the second metal layer, thereby improving manufacturing precision while maintaining the reduced fanout region width achieved by the double-layer metal wiring method
Solution Approach 2:
The flat layer acts as an intermediary between the unflat first insulating layer and the second metal layer. It mediates the surface non-uniformity issue, allowing the photoresist to be coated uniformly on the second metal layer despite the underlying insulating layer being non-uniform, thus resolving the contradiction between compact wiring and manufacturing precision
2Length of moving object
If the fanout pitch is reduced to achieve narrow bezels, then the bezel width is reduced, but the fabrication accuracy deteriorates due to non-uniform second metal layer caused by unflat insulating layers
Solution Approach 1:
The flat layer is formed as a preliminary structure before depositing the second metal layer. This ensures that even when reducing fanout pitch for narrow bezels, the second metal layer can be fabricated with high accuracy and consistent line widths and spacings, as the flat layer provides a uniform surface that eliminates distortion from the unflat insulating layer
Solution Approach 2:
The flat layer serves as an intermediary that decouples the fanout pitch reduction from fabrication accuracy degradation. It allows the second metal layer to be formed with precise dimensions regardless of the compressed fanout pitch, enabling narrow bezel design without sacrificing manufacturing quality
Data Source
AI summary
Disclosed are a display substrate, a fabrication method for the display substrate, and a display device. By arranging a flat layer with a flat surface facing the second metal layer between a first metal layer and a second metal layer, the second metal layer deposited on the flat layer is also relatively flat, so that the second metal wirings with the same width and spacing as that of first metal wirings can be formed. The etching resolutions of the metal wirings in the fanout region corresponding to the first metal layer and the second metal layer in the solutions of the present disclosure can be the same.