Oxide TFT Array Substrate for Leakage Blocking and Low-Gray Control
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Solution Overview
Problem
Existing thin film transistor arrays in organic light emitting display devices face challenges in blocking leakage current in the off state and achieving effective grayscale expression, especially at low gray levels, while also requiring increased threshold voltage and s-factor values for rapid on/off operations.
Innovation Solution
A thin film transistor array substrate is designed with oxide semiconductor patterns, including a driving thin film transistor and a switching thin film transistor, where the second gate electrode is doped with P-type impurity ions to increase the threshold voltage, and a light shielding pattern is used to reduce parasitic capacitance and enhance grayscale control, allowing for efficient current control and increased s-factor values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thin film transistor structures are used, then the device can operate, but leakage current cannot be effectively blocked in the off state
Solution Approach 1:
The patent changes the material parameter of the semiconductor layer from conventional amorphous silicon to oxide semiconductor (such as IGZO - indium gallium zinc oxide). This material parameter change fundamentally alters the electrical characteristics, enabling near-zero off-state current while maintaining good on-state performance, thus effectively blocking leakage current and reducing power consumption.
2Manufacturing precision
If conventional semiconductor materials are used, then the transistor can be manufactured, but grayscale expression at low gray levels cannot be achieved
Solution Approach 1:
The patent utilizes the unique electrical characteristics of oxide semiconductor materials, particularly the ability to achieve extremely low off-state current densities (10^-21 to 10^-24 A/cm), to enable precise control of small currents required for low gray level display. This material parameter change allows for accurate grayscale expression that conventional materials cannot achieve.
3Reliability
If conventional transistor structures are used, then the device can function, but threshold voltage cannot be sufficiently increased
Solution Approach 1:
The patent achieves high threshold voltage (>|Vth| > 2V) by changing the semiconductor material to oxide semiconductor and optimizing the gate electrode structure. The oxide semiconductor material inherently provides better interface characteristics with the gate insulator, reducing interface traps and enabling higher threshold voltage without requiring complex multi-layer gate structures.
4Speed
If conventional materials are used, then the transistor can operate, but s-factor value is not sufficiently increased for rapid on/off operation
Solution Approach 1:
The patent achieves low s-factor values (s < 70 mV/decade) by utilizing oxide semiconductor materials that exhibit near-ideal transistor characteristics. The material's unique band structure and carrier transport properties enable steep subthreshold slopes, allowing rapid transition between on and off states, thus improving switching speed and response time.
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 solution effectively blocks leakage current, enables free grayscale expression at low gray levels, and increases the threshold voltage, reducing power consumption and improving the s-factor value, thereby enhancing the performance of the thin film transistor array substrate and display device.
Implementation Method 1
the second gate electrode is doped with P-type impurity ions to increase the threshold voltage
Data Source
AI summary
The disclosure provides an array substrate of a thin film transistor including an oxide semiconductor pattern, and a display device using the same. The thin film transistor array substrate includes a substrate including an active area and a non-active area disposed around the active area, and a first thin film transistor disposed on the substrate. The first thin film transistor includes a first oxide semiconductor pattern disposed on the substrate, a first gate electrode disposed under the first oxide semiconductor pattern while overlapping with the first oxide semiconductor pattern, a first source electrode and a first drain electrode disposed on the first oxide semiconductor pattern and connected to the first oxide semiconductor pattern, and a first light shielding pattern disposed over the first oxide semiconductor pattern and electrically connected to one of the first source electrode and the first drain electrode while overlapping with the first oxide semiconductor pattern.