Transparent Storage Capacitor Electrode for Aperture Ratio
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Solution Overview
Problem
In display devices, increasing the area of the storage capacitor to maintain voltage leads to a reduction in the aperture ratio due to the use of opaque conductive layers, and causes haze in transparent conductive layers formed through high-temperature deposition, while also resulting in signal delays from contact resistance issues.
Innovation Solution
A thin film transistor (TFT) array substrate with a storage capacitor electrode formed as a transparent conductive layer after the active layer formation, which secures sufficient storage capacitor area without reducing the aperture ratio and prevents haze by using a transparent conductive layer, and includes a method to manufacture this substrate with specific layer formations and contact holes to minimize contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the storage capacitor is increased to maintain voltage, then the storage capacitance is improved, but the aperture ratio is reduced due to opaque conductive layers
Solution Approach 1:
The patent changes the material parameter of the storage capacitor electrode from opaque conductive material to transparent conductive material (such as ITO, IZO, or TCO). This parameter change allows the electrode to be transparent, thereby maintaining the aperture ratio while providing sufficient storage capacitance area.
Solution Approach 2:
The patent employs composite material structure by combining transparent conductive layer with insulating layers to form the storage capacitor. The transparent conductive electrode is combined with insulating materials to create a functional composite structure that achieves both electrical functionality and optical transparency.
2Area of stationary object
If a transparent conductive layer is used for the storage capacitor electrode, then the aperture ratio is maintained, but haze is generated due to high temperature deposition
Solution Approach 1:
The patent applies preliminary action by forming the transparent conductive layer for the storage capacitor electrode before subsequent high-temperature processing steps. Specifically, the transparent conductive layer is deposited early in the manufacturing process, and then later high-temperature steps (such as sintering or annealing) are performed without re-heating the transparent conductive layer to excessive temperatures that would cause haze.
Solution Approach 2:
The patent controls the deposition temperature parameter of the transparent conductive layer to be within a specific range (typically below 200°C) to prevent haze formation. Additionally, the patent adjusts subsequent processing temperatures and timing to ensure the transparent conductive layer is not exposed to high temperatures that would cause haze while still achieving the required storage capacitance.
3Productivity
If the storage capacitor electrode is formed early in the process, then manufacturing efficiency is improved, but contact resistance between common line and storage electrode increases
Solution Approach 1:
The patent segments the storage capacitor electrode formation process into distinct stages: first forming the transparent conductive layer, then creating contact holes to expose the common line, and finally establishing electrical connection. This segmentation allows for optimized processing at each stage, reducing contact resistance while maintaining manufacturing efficiency.
Solution Approach 2:
The patent introduces an intermediary structure (contact hole through insulating layers) to facilitate reliable electrical connection between the transparent conductive storage electrode and the common line. This intermediary approach ensures low contact resistance by providing a direct conductive path through the insulating barrier.
Data Source
AI summary
A thin film transistor array substrate and its manufacturing method are disclosed. A thin film transistor (TFT) includes a gate electrode formed on a substrate, and source and drain electrodes formed on the gate electrode and separated from each other. A common line made of the same material as the gate electrode is formed on the substrate. A storage capacitor includes a storage electrode connected with a storage electrode line and a pixel electrode formed on the storage electrode. The storage electrode and the pixel electrode are formed by patterning a transparent conductive film, and accordingly, light can be transmitted through the region where the storage capacitor is formed to thus increase an aperture ratio.