Array Substrate Stepped Hole Passivation Layer Curling
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Solution Overview
Problem
Conventional array substrates face high defect rates due to curling and falling off of the passivation layer near the pixel electrode, resulting in dark spot defects in liquid crystal panels, caused by the segment difference between the passivation layer and the pixel electrode.
Innovation Solution
The array substrate features a stepped hole in the planarization layer with a diameter decreasing from the side facing away the substrate towards the side facing the substrate, where the pixel electrode is formed, reducing the segment difference and preventing curling and falling off of the passivation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pixel electrode protrudes from the planarization layer, then the pixel electrode can be properly formed and connected, but the passivation layer forms a segment difference equal to the thickness of the pixel electrode, causing curling and falling off
Solution Approach 1:
The via hole in the planarization layer is divided into two parts: a first part extending from the upper surface to a first depth, and a second part extending from the upper surface to a second depth greater than the first depth. This segmentation allows different regions of the via hole to serve different functions - the first part accommodates the pixel electrode while the second part provides additional support, reducing the segment difference of the passivation layer and preventing curling and falling off.
Solution Approach 2:
Different regions of the via hole are given different depths and characteristics. The first part of the via hole has a specific depth to accommodate the pixel electrode, while the second part extends deeper to provide additional anchoring. This local differentiation in via hole structure allows the passivation layer to maintain better adhesion and reduce segment difference without affecting the overall pixel electrode formation.
2Reliability
If the passivation layer is formed to cover the pixel electrode, then electrical insulation is provided, but the segment difference causes the passivation layer to curl and fall off near the pixel electrode
Solution Approach 1:
The via hole structure is designed with a second part extending deeper than the first part, creating a cushioning effect before the passivation layer is formed. This deeper extension provides additional support and reduces the segment difference that would otherwise cause the passivation layer to curl and fall off, preventing the defect before it occurs.
Solution Approach 2:
The second part of the via hole acts as an intermediary structure between the pixel electrode and the passivation layer. It provides a transition zone that reduces the abrupt thickness change, thereby reducing the segment difference and preventing the passivation layer from curling and falling off.
3Productivity
If a conventional via hole structure is used, then the manufacturing process is simple, but the segment difference leads to high defect rates and dark spot defects
Solution Approach 1:
The via hole is segmented into two parts with different depths, which can be formed using standard photolithography and etching processes with a multi-layer mask approach. This segmentation reduces the segment difference and improves yield without requiring fundamentally new manufacturing equipment or processes, thus maintaining reasonable manufacturing complexity while significantly improving productivity.
Data Source
AI summary
The present application provides an array substrate and a method of manufacturing the same. The array substrate includes a first substrate having a drain electrode protruding from a side of the first substrate; a planarization layer at the side of the first substrate where the drain electrode protrudes, the planarization layer being provided with a stepped hole on the drain electrode, and a diameter of the stepped hole decreasing along a direction from a side of the planarization layer facing away the first substrate towards a side of the planarization layer facing the first substrate; a pixel electrode at the stepped hole and connected with the drain electrode; a passivation layer covering the planarization layer and the pixel electrode; and a common electrode on the passivation layer.