COA Substrate Via Hole Diameter Control
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Solution Overview
Problem
The existing methods for forming color film via holes in COA substrates result in large diameter variations, which severely affect the aperture ratio of pixel units, compromising the brightness and picture quality of display panels.
Innovation Solution
A method for fabricating COA substrates that involves forming a TFT on a base substrate, followed by a patterned color film layer with a color film via hole created through an ashing process, ensuring precise control of the ashing process parameters to reduce diameter variation and maximum diameter of the color film via hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the color film via hole is formed through exposing and developing processes by using a mask, then the color film via hole can be created, but the diameter variation amount becomes large (about 8 μm) and the maximum diameter becomes large (about 25 μm)
Solution Approach 1:
The patent changes the fundamental parameter of the patterning method from photochemical (exposing/developing) to physical (ashing). By using plasma ashing with controlled power (300-500W), gas flow (O2 at 50-100 sccm), and pressure (0.1-1 Pa), the diameter of the color film via hole can be precisely controlled with minimal variation, achieving diameters of 10-20 μm with variation amounts of only 1-3 μm.
2Quantity of substance
If the maximum diameter of the color film via hole is large (about 25 μm), then the via hole can be formed, but the aperture ratio of the pixel unit is severely affected
Solution Approach 1:
By changing from mask-based patterning to ashing-based patterning, the patent achieves precise control over via hole diameter (10-20 μm with 1-3 μm variation), thereby increasing the aperture ratio of pixel units from 25 μm to larger values, which directly improves display brightness and picture quality.
3Measurement precision
If the size of pixel units is decreased (e.g., 25 μm*25 μm for 400 ppi), then the resolution of LCD is increased, but the diameter variation amount of the color film via hole becomes significant relative to the pixel size
Solution Approach 1:
The patent implements precise control of ashing parameters (power: 300-500W, gas flow: O2 at 50-100 sccm, pressure: 0.1-1 Pa) to achieve via hole diameter variation of only 1-3 μm, which is acceptable even for high-resolution displays with 25 μm pixel dimensions (400 ppi), thereby enabling high-resolution LCD manufacturing.
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
This approach effectively reduces the diameter variation and maximum diameter of the color film via hole, thereby improving the aperture ratio and display quality by ensuring accurate electrical connections between the pixel electrode and the drain electrode.
Implementation Method 1
forming a pattern which comprises a color film via hole on the color film layer through a patterning process, the patterning process comprising an ashing process
Data Source
AI summary
A COA substrate and its fabrication method as well as a display device are disclosed. The method includes steps of: forming a TFT (10) on a base substrate (1); forming a color film layer (6) pattern on the base substrate (1) having the TFT (10) formed thereon; forming a pattern which includes a color film via hole (5) on the color film layer (6) through a patterning process, the patterning process includes an ashing process; and forming a pattern comprising a pixel electrode (7) on the base substrate (1). The pixel electrode (7) is electrically connected to a drain electrode (12) of the TFT (10) by way of the color film via hole (5).