Oxide TFT Gate Pad Metal Layer Prevents Passivation Overhang
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Solution Overview
Problem
The existing LCD devices with oxide TFTs face challenges in the fabrication process due to the difference in etching methods between the nitride-based gate insulating layer and oxide-based passivation layer, leading to the generation of overhangs and disconnection of transparent conductive layers, which complicates the process and increases costs.
Innovation Solution
A metal layer is formed between the gate insulating layer and the passivation layer on the gate pad area to prevent overhang generation during etching, making the etching processes of the gate insulating and passivation layers independent of each other, thus simplifying the fabrication process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If different etching methods are used for nitride-based gate insulating layer and oxide-based passivation layer, then the etching processes can be optimized for each layer, but overhangs are generated and transparent conductive layers become disconnected
Solution Approach 1:
The patent applies homogeneity by forming the same metal layer material (e.g., aluminum or its alloy) on both the gate pad and the data pad. This uniform material selection ensures consistent etching behavior and eliminates the need for different etching methods, thereby preventing overhang formation and maintaining process simplicity while achieving precise pattern formation.
2Manufacturing precision
If additional steps are added to remove overhangs, then overhang generation is eliminated, but the fabrication process becomes more complex and costly
Solution Approach 1:
The patent applies preliminary action by pre-forming the metal layer on the gate pad and data pad before the transparent conductive layer deposition. This advance preparation ensures that the metal layer serves as a protective and supportive structure, preventing overhang formation during subsequent etching processes and eliminating the need for additional overhang removal steps, thereby simplifying the overall fabrication process.
3Reliability
If oxide TFTs are used to improve electrostatic properties and mobility, then device performance is improved, but the fabrication process becomes more complex due to different material requirements
Solution Approach 1:
The patent applies parameter changes by optimizing the metal layer thickness and material composition to achieve the desired electrical conductivity and crystallinity. By carefully controlling these parameters, the patent enables the use of oxide TFTs with improved electrostatic properties and mobility while maintaining a simplified fabrication process that does not require excessively complex additional steps.
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 simplifies the fabrication process and reduces costs by eliminating the need for additional steps to remove overhangs, ensuring consistent and efficient formation of the oxide TFTs with improved electrical conductivity and crystallinity.
Implementation Method 1
A metal layer is formed between the gate insulating layer and the passivation layer on the gate pad area to prevent overhang generation during etching
Implementation Method 2
etching the oxide semiconductor material at the pixel area to form an oxide semiconductor layer over the gate electrode, etching the oxide semiconductor material and an the gate insulating material at the gate pad area to expose a gate pad
Implementation Method 3
depositing a nitride-based gate insulating material and an oxide semiconductor material on the entire surface of the first substrate
Data Source
AI summary
A display device including an oxide thin film transistor (TFT) is disclosed. A nitride-based gate insulating layer of a gate pad area is etched when an oxide semiconductor layer of a pixel area is etched by using a half-tone mask, a metal layer is formed at a contact hole of the etched gate insulting layer, and then a passivation layer formed thereon is etched. Thus, an overhang of the passivation layer can be prevented from being generated when the gate insulating layer is etched, and accordingly, the fabrication process can be simplified.