Oxide TFT Etch Stopper Layer Design for Threshold Voltage Stability
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Solution Overview
Problem
Conventional oxide thin film transistors (TFTs) used in display panels are sensitive to environmental moisture and oxygen, leading to unstable threshold voltages, which can result in abnormal display conditions such as multi-pulse conditions in gate driving circuits and image abnormalities due to low threshold voltages.
Innovation Solution
The method involves forming first and second thin film transistors on a substrate with different etch stopper layers, where the threshold voltage of the second TFTs is higher than that of the first TFTs, using materials like silicon dioxide and varying the ratio of nitrous oxide and silane gases in the chemical vapor deposition process, or employing physical vapor deposition to ensure stability and prevent threshold voltage shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxide TFTs are used to form the array substrate, then the resolution of the display panel is improved and manufacture cost is reduced, but the threshold voltage becomes unstable due to sensitivity to environmental moisture and oxygen
Solution Approach 1:
The patent applies parameter changes by modifying the etch stopper layer composition (using different ratios of nitrous oxide and silane gases in CVD, or using PVD instead) to control the threshold voltage of oxide TFTs. This allows the threshold voltage to be adjusted to appropriate levels while maintaining the benefits of oxide TFTs for high resolution and low cost manufacturing.
2Ease of manufacture
If the threshold voltage is too low, then the manufacturing cost is reduced, but the gate driving circuit exhibits abnormal multi-pulse conditions and the display panel shows abnormal display
Solution Approach 1:
The patent applies local quality by using different etch stopper layer configurations for different regions of the array substrate. Specifically, different ratios of nitrous oxide and silane gases are used for different TFTs, or different deposition methods (CVD vs PVD) are applied to different regions, allowing optimization of threshold voltage for specific circuit functions while maintaining overall manufacturing efficiency.
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 prevents abnormal multi-pulse conditions in gate driving circuits and image abnormalities by using high-threshold voltage TFTs for gate driving circuits and low-threshold voltage TFTs for pixel driving, enhancing stability and maintaining image quality.
Implementation Method 1
varying the ratio of nitrous oxide and silane gases in the chemical vapor deposition process
Implementation Method 2
employing physical vapor deposition to ensure stability and prevent threshold voltage shifting
Data Source
AI summary
The disclosure provides a display panel, an array substrate and a fabrication method thereof. The fabrication method of the array substrate includes forming a plurality of first thin film transistors and a plurality of second thin film transistors on the first substrate. The etch stopper layer of the second thin film transistor is different from an etch stopper layer of the first thin film transistor, and a threshold voltage of the second thin film transistor is higher than a threshold voltage of the first thin film transistor. By using the disclosed thin film transistors to form the gate driving circuit, the second thin film transistor with a high threshold voltage can be used as the driving signal outputting transistor. The abnormal multi-pulse of the gate driving circuit and the display panel caused by the low threshold voltage of the second thin film transistors may be therefore avoided.