Thin Film Transistor Metal Patterning for Light Shielding
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Solution Overview
Problem
Conventional passivation layers in thin film transistors, such as silicon oxide or silicon nitride, fail to effectively block visible and UV light, which can affect the properties of indium gallium zinc oxide (IGZO) thin films, leading to instability and increased power consumption in LCDs.
Innovation Solution
A thin film transistor design with a metal patterning layer and passivation layer is implemented, where the metal patterning layer is positioned above the insulating layer to expose portions of the metal oxide semiconductor layer, increasing oxygen vacancy density and conductivity, and the passivation layer is used to cover the structure, effectively isolating the metal oxide semiconductor from water, oxygen, and light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional passivation layers (silicon oxide or silicon nitride) are used to protect the metal oxide semiconductor layer, then water and oxygen penetration is prevented, but visible and UV light cannot be effectively blocked
Solution Approach 1:
The patent employs a composite passivation structure combining multiple material layers: a metal layer (Al, Mo, or Ti) serving as the primary light-blocking layer, coupled with silicon oxide or silicon nitride layers for water and oxygen barrier functions. This composite approach allows each material to address its specific protective function, with the metal layer blocking visible and UV light while the silicon-based layers prevent moisture and oxygen penetration, thereby achieving comprehensive protection against all harmful factors simultaneously.
2Reliability
If the metal oxide semiconductor layer is fully covered by passivation layers, then protection is provided, but oxygen vacancy density and conductivity cannot be enhanced
Solution Approach 1:
The patent implements local quality differentiation in the passivation structure by creating selective openings in the metal layer and insulating layer to expose specific regions of the metal oxide semiconductor layer. These localized exposed regions serve as conductive channels with enhanced oxygen vacancy density, while other regions remain covered by the passivation layers for protection. This spatial differentiation allows simultaneous achievement of high conductivity in channel regions and environmental protection in non-channel regions.
3Object-affected harmful factors
If a metal patterning layer is added to block light, then light penetration is prevented, but device complexity increases
Solution Approach 1:
The metal layer in the patent serves multiple functions simultaneously: it acts as a light-blocking layer to prevent visible and UV light penetration, functions as part of the passivation structure to protect the metal oxide semiconductor layer, and can be integrated with existing electrode patterns in the display device. By designing the metal layer with dual functionality (light blocking + structural integration), the patent avoids adding excessive complexity while achieving effective light protection.
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 increased oxygen vacancy density in the exposed metal oxide semiconductor layer enhances conductivity and stability, reducing power consumption and maintaining the integrity of the thin film transistor against environmental factors, while the passivation layer prevents light penetration and current leakage.
Implementation Method 1
the exposed metal oxide semiconductor layer has a higher density of oxygen vacancy than the unexposed metal oxide semiconductor layer. Therefore, the exposed metal oxide semiconductor layer has a higher conductivity than the unexposed metal oxide semiconductor layer
Implementation Method 2
the thin film of silicon oxide or silicon nitride cannot effectively block the light in the visible to the UV region to irradiating on the a-IGZO thin film
Implementation Method 3
the passivation layer of TFTs mostly uses a thin film of silicon oxide or silicon nitride to prevent the penetration of water and oxygen
Implementation Method 4
a thermal annealing process is performed before patterning the metal layer to treat the metal oxide semiconductor layer
Data Source
AI summary
A thin film transistor and a fabrication method thereof are provided. A metal patterning layer is formed on the metal oxide semiconductor layer of a thin film transistor to shield the metal oxide semiconductor layer from the water, oxygen and light in the environment.