Dual-Layer Passivation for Regular Contact Holes in LCD TFTs
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Solution Overview
Problem
Irregular vertical profiles of contact holes in the passivation layer of LCD devices can disconnect thin film transistors (TFTs) from pixel electrodes, leading to malfunctions in display devices.
Innovation Solution
A passivation layer assembly comprising a first and second passivation layer with different etching rates is used, where the second passivation layer has a higher etching rate than the first, ensuring a regular cross-section of the contact hole and secure connection between the TFT and pixel electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single passivation layer is used and etched to form contact holes, then the manufacturing process is simple, but the contact hole vertical profile becomes irregular causing TFT disconnection
Solution Approach 1:
The single passivation layer is divided into two separate passivation layers with different etching rates. The first passivation layer has a slower etching rate to maintain a vertical profile at the bottom of the contact hole, while the second passivation layer has a faster etching rate to complete the hole formation, thereby achieving a regular vertical cross-section
Solution Approach 2:
Different regions of the passivation layer structure are assigned different etching characteristics. The first passivation layer is designed with specific material composition to provide slow etching rate for vertical wall formation, while the second passivation layer uses different material properties to enable faster etching for efficient hole completion
2Productivity
If the contact hole vertical profile is irregular, then the etching process is simpler, but the TFT becomes disconnected from the pixel electrode causing device malfunction
Solution Approach 1:
The passivation layer is segmented into two layers with differentiated etching rates, allowing the etching process to first create a vertical profile through the slower-etching first layer, then complete the contact hole through the faster-etching second layer, ensuring both connection reliability and process efficiency
Solution Approach 2:
The etching rate parameter is changed between the two passivation layers by selecting materials with different chemical or physical properties. This parameter variation enables the formation of a regular vertical cross-section that ensures reliable TFT-to-pixel-electrode connection while maintaining acceptable manufacturing efficiency
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
The solution prevents malfunctions in LCD devices by ensuring a secure connection between the TFT and pixel electrode through the formation of a contact hole with a regular cross-section, enhancing the reliability of the display device.
Implementation Method 1
The first passivation layer has a first etching rate with respect to an etching agent. The second passivation layer has a second etching rate that is higher than the first etching rate with respect to the etching agent.
Data Source
AI summary
A passivation layer assembly and a display substrate having the same are presented. The passivation layer assembly is positioned on a substrate having a thin film assembly and protects the thin film assembly. The thin film assembly includes a first passivation layer and a second passivation layer. The first passivation layer contacts the thin film assembly. The first passivation layer has a first etching rate with respect to an etching agent. The second passivation layer is on the first passivation layer. The second passivation layer has a second etching rate that is higher than the first etching rate with respect to the etching agent. The passivation assembly decrease the malfunction rate of the display device.