Photosensitive Passivation Layer for Thin Film Transistors
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Solution Overview
Problem
Conventional TFT array substrate fabrication processes are complex and costly due to the need for multiple photolithography steps, leading to increased process defects, processing time, and material costs, while the use of inorganic insulating materials for passivation layers reduces the aperture ratio and causes parasite capacitance, and organic materials increase layer thickness, limiting lightness.
Innovation Solution
A TFT array substrate with a passivation layer made from a sol compound of metal alkoxide and silicon alkoxide with photosensitive groups, or a material with nanoparticles dispersed in a polymer matrix, which serves both as a film passivation and photoresist layer, allowing direct light exposure and development to form contact holes without additional photoresist processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photolithography steps are used to form TFT array substrate patterns, then manufacturing precision is improved, but device complexity and productivity are worsened
Solution Approach 1:
The patent combines the passivation layer and photoresist layer into a single integrated layer structure. The passivation layer material itself possesses photosensitive properties, eliminating the need for a separate photoresist layer. This merging reduces the number of photolithography steps from multiple sequential processes to a simplified multi-layer deposition approach where each layer serves dual functions (passivation and patterning).
Solution Approach 2:
The passivation layer is designed to perform multiple functions simultaneously: it provides electrical insulation, protects underlying structures, and serves as the photoresist layer for pattern formation. This multi-functionality eliminates the need for dedicated photoresist materials and reduces the overall process complexity while maintaining manufacturing precision.
2Stability of the object's composition
If inorganic insulating materials are used for passivation layers, then thermal stability is improved, but aperture ratio is worsened due to parasite capacitance
Solution Approach 1:
The patent employs composite material structures where organic and inorganic layers are combined in a stacked configuration. The organic passivation layer (with low dielectric constant) is deposited over inorganic layers, creating a composite structure that leverages the low-k properties of organic materials to reduce parasite capacitance while maintaining the thermal stability benefits of underlying inorganic layers.
3Area of stationary object
If organic materials are used for passivation layers, then aperture ratio is improved by reducing parasite capacitance, but layer thickness increases limiting lightness
Solution Approach 1:
The patent utilizes plasma-enhanced chemical vapor deposition (PECVD) to deposit organic passivation layers at low temperatures, enabling precise control of layer thickness and dielectric constant parameters. By adjusting deposition parameters such as temperature, pressure, and gas flow rates, the process achieves thin layer formation with optimized electrical properties, reducing both thickness and parasite capacitance simultaneously.
4Manufacturing precision
If conventional photolithography processes are used, then manufacturing precision is improved, but material costs and processing time increase
Solution Approach 1:
The passivation layer is designed with inherent photosensitive properties during the material selection and deposition stages. This preliminary incorporation of photosensitivity eliminates the need for subsequent photoresist coating and stripping operations, reducing processing time while maintaining pattern formation precision through the integrated layer 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
This approach simplifies the fabrication process, reduces material costs, enhances thermal stability, and maintains a high aperture ratio by eliminating parasite capacitance, while allowing for precise control of dielectric constants and transmittance.
Implementation Method 1
a passivation layer formed over an entire upper surface of the substrate including the source electrode and the drain electrode, the passivation layer being made of a sol compound of a metal alkoxide having a photosensitive group X and a silicon alkoxide having a photosensitive group Y
Implementation Method 2
a material with nanoparticles dispersed in a polymer matrix, which serves both as a film passivation and photoresist layer
Data Source
AI summary
A thin film transistor (TFT) array substrate and a method for fabricating the thin film transistor (TFT) array substrate is disclosed, wherein a passivation layer is directly subjected to exposing and patterning processes without using any photoresist, thereby simplifying the fabrication process and ensuring reduced preparation costs. In particular, the method comprises a thin film transistor (TFT) array comprising: forming a gate line and a gate electrode on a substrate; forming a semiconductor layer to be insulated from the gate electrode, and overlapped with a portion of the gate electrode; forming a source electrode and a drain electrode on both sides of the semiconductor layer, respectively, while forming a data line intersecting with the gate line; forming a passivation layer over an entire upper surface of the substrate including the source electrode and the drain electrode using a sol compound of a metal alkoxide having a photosensitive group X and a silicon alkoxide having a photosensitive group Y; light-exposing and developing the passivation layer to form a contact hole through which the drain electrode is exposed; and forming a pixel electrode to be in contact with the drain electrode through the contact hole.