Oxide TFT Passivation Layer Structure for Permeation Control
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Solution Overview
Problem
The existing array substrates using oxide TFTs are prone to performance degradation due to permeation of water, oxygen, and hydrogen groups from the passivation layer, leading to shifts in threshold voltage and potential device failure.
Innovation Solution
A passivation layer comprising a silicon oxide film as the first film layer and an alternate stack of thin silicon nitride and silicon oxide films as the second film layer, where the silicon nitride films and silicon oxide films compensate for each other's limitations, reducing permeability and enhancing protection against water, oxygen, and hydrogen ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer is used to protect the oxide TFT, then the device structure is completed and basic protection is provided, but water, oxygen and hydrogen groups permeate through the passivation layer, causing threshold voltage shift and performance degradation
Solution Approach 1:
The patent employs a composite passivation layer structure consisting of multiple film layers with different material compositions (silicon oxide, silicon nitride, and organic insulating materials). This composite structure leverages the complementary properties of each material: silicon oxide provides good interface characteristics, silicon nitride offers low permeability to water and oxygen, and organic insulating materials contribute to overall insulation. The synergistic combination of these materials creates a passivation layer that effectively prevents permeation of harmful substances while maintaining device stability.
Solution Approach 2:
The passivation layer is divided into multiple discrete film layers (first film layer, second film layer, and third film layer) rather than using a single homogeneous layer. Each film layer has specific thickness and material properties optimized for particular functions. This segmentation allows the harmful substances to be blocked at multiple interfaces and barriers, preventing any single layer from being a weak point for permeation.
2Object-affected harmful factors
If the passivation layer is made thicker to improve protection, then permeation resistance increases, but the device structure becomes more complex and manufacturing difficulty increases
Solution Approach 1:
Instead of increasing the thickness of a single material layer, the patent uses composite materials with different functional properties. Each material in the composite structure contributes specific characteristics: silicon nitride provides low permeability, silicon oxide provides good interface quality, and organic insulating materials provide electrical insulation. This approach achieves high permeation resistance without requiring excessive total thickness, thereby controlling structural complexity.
Solution Approach 2:
Different film layers within the passivation structure have different thicknesses and material properties optimized for their specific locations and functions. The first film layer (silicon oxide) has a thickness of 50-200 nm for interface quality, the second film layer (silicon nitride) has 20-100 nm for permeation blocking, and the third film layer (organic insulating material) has 50-200 nm for insulation. This local optimization of quality parameters achieves effective protection while maintaining reasonable overall structure.
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 proposed solution effectively prevents the permeation of water, oxygen, and hydrogen groups, ensuring the stability and reliability of the oxide TFTs, thereby maintaining performance and preventing device failure.
Implementation Method 1
the silicon nitride films and the silicon oxide films in the second film layer make up for each other, which not only reduces adverse effect brought by longitudinal permeability of the silicon nitride film but also reduces adverse effect brought by low compactness of the silicon oxide film
Data Source
AI summary
The present invention discloses an array substrate and a preparation method thereof, a display panel and a display device, so as to solve the problem that the performance of the oxide TFT may be reduced and even out of work due to relatively great shift of the threshold voltage of the oxide TFT since the water, oxygen and hydrogen groups may permeate to the active layer of the oxide TFT from the passivation layer above the oxide TFT. The array substrate comprises a base substrate, an oxide thin film transistor TFT formed on the base substrate, a passivation layer being arranged above the oxide TFT, the passivation layer comprises a first film layer, the first film layer being a silicon oxide film; the passivation further comprises a second film layer formed on the first film layer, the second film layer is an alternate stack of silicon nitride films and silicon oxide films, a base layer of the second film layer close to the first film layer is a silicon nitride film; wherein the thickness of the first film layer is greater than the thickness of the second film layer.