TFT Array Substrate with Dual Dielectric Layers for Storage Capacitor
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Solution Overview
Problem
Conventional TFT-LCDs face issues with reduced aperture ratio due to opaque storage capacitors and identical dielectric layers for gate and storage capacitors, limiting independent capacitance control and hindering thinning of dielectric layers.
Innovation Solution
A method for forming a TFT array substrate with a thinner dielectric layer for the storage capacitor, involving partial removal of the first dielectric layer and using a second dielectric layer between the bottom and top electrodes, allowing independent control of capacitance values without increasing the mask count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the storage capacitor uses the same dielectric layer as the gate capacitor, then the manufacturing process is simplified, but the capacitance values cannot be independently controlled and the aperture ratio is reduced
Solution Approach 1:
The patent divides the capacitor structure into two independent parts: gate capacitor and storage capacitor. Each capacitor has its own separate dielectric layer (gate dielectric layer and capacitor dielectric layer) and electrode structure, allowing independent design and control of capacitance values for each capacitor type.
Solution Approach 2:
The patent applies different dielectric materials and thicknesses to different locations in the device. The gate dielectric layer and capacitor dielectric layer use different materials (such as silicon oxide vs. silicon nitride) and different thicknesses, enabling different capacitance densities in different regions while maintaining a unified manufacturing process.
2Manufacturing precision
If the dielectric layer is made thicker to increase storage capacitance, then the capacitance value increases, but the aperture ratio is reduced due to increased pixel area occupation
Solution Approach 1:
The patent uses composite dielectric structures with different materials having different dielectric constants. By combining materials like silicon oxide (lower dielectric constant) and silicon nitride (higher dielectric constant) in different layers and thicknesses, the design achieves high capacitance density without requiring excessive thickness, thus preserving aperture ratio.
3Manufacturing precision
If the storage capacitor dielectric layer is made opaque to ensure sufficient capacitance, then the capacitance value is adequate, but the aperture ratio and pixel quality deteriorate
Solution Approach 1:
The patent employs transparent or translucent dielectric materials for the capacitor dielectric layer, allowing light to pass through the storage capacitor region. This maintains pixel optical quality while achieving sufficient capacitance through optimized dielectric material selection and thickness control, rather than relying on opaque materials.
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 enhances the aperture ratio of TFT-LCDs by achieving higher capacitance values for the storage capacitor per unit area, enabling thinner dielectric layers and improved pixel quality.
Implementation Method 1
a first dielectric layer disposed on the active layer, a second dielectric layer disposed on the first dielectric layer, wherein the second dielectric layer is disposed between the bottom electrode and the top electrode
Implementation Method 2
The liquid crystal layer interposed between the common electrode and the pixel electrode forms a capacity of liquid crystal
Implementation Method 3
performing an implantation to form source/drain regions 5 in the first active layer 2a of the driver area 16, source/drain regions 15 in the third active layer 2c of the pixel area 22 and an n+ type doped bottom electrode 2d in the pixel area 22
Data Source
AI summary
A system for display images comprising a thin film transistor array substrate is disclosed. The system for display images comprises a substrate having a pixel area, a source/drain region overlying the substrate within an active layer in the pixel area, a bottom electrode overlying the substrate in the pixel area, a top electrode overlying the bottom electrode, a first dielectric layer disposed on the active layer, a second dielectric layer disposed on the first dielectric layer, wherein the second dielectric layer is disposed between the bottom electrode and the top electrode and a gate disposed overlying the active layer, wherein the first and second dielectric layers are interposed between the gate and the active layer.