TFT Array Substrate Stack Structure for Contact Hole Fabrication
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Solution Overview
Problem
Current etching techniques struggle to fabricate contact holes with high aspect ratios on color resist in LCDs, leading to a dilemma where contact holes must be designed with large areas to ensure yield, which negatively impacts pixel aperture ratio and display brightness.
Innovation Solution
A TFT array substrate design that uses a stack structure to raise the extended electrode of the drain electrode, allowing the contact hole to be less deep and smaller in area, thereby promoting the pixel aperture ratio without compromising the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the area of the contact hole is made smaller to increase pixel aperture ratio, then the pixel aperture ratio is improved, but the contact hole cannot pass through the insulation layer smoothly due to etching technique limitations
Solution Approach 1:
The patent introduces a stack structure that raises the extended electrode of the drain electrode vertically, changing the spatial dimension of the contact hole position. This allows the contact hole to be shallower and smaller in area while still reaching the extended electrode, thereby increasing the pixel aperture ratio without compromising manufacturing feasibility
Solution Approach 2:
The extended electrode acts as an intermediary element between the drain electrode and the pixel electrode. By extending the drain electrode and raising it through the stack structure, it creates an intermediate contact point that is more accessible to etching processes, enabling smaller contact holes to successfully reach the conductive layer
2Manufacturing precision
If the contact hole area is made larger to ensure smooth etching process, then the manufacturing precision is improved, but the pixel aperture ratio is reduced
Solution Approach 1:
By raising the extended electrode through the stack structure, the contact hole needs to traverse less insulation layer depth, allowing for smaller contact hole area while maintaining etching process reliability. This dimensional change decouples the relationship between contact hole size and etching difficulty
Data Source
AI summary
A thin film transistor (TFT) array substrate includes a stack structure disposed to raise an extended electrode of a drain electrode of a thin film transistor. Therefore, a contact hole does need to be very deep to expose the extended electrode of the drain electrode.