Compensation TFT Leakage Current Reduction via Localized Plasma and Laser Annealing
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Solution Overview
Problem
Display devices experience flickering when displaying still images at low frequencies due to significant leakage currents in thin film transistors, which affect the brightness and stability of the image.
Innovation Solution
The design incorporates a compensation thin film transistor with a semiconductor layer that has a lower grain boundary trap density and higher hydrogen concentration, treated with hydrogen-plasma and excimer laser annealing, to minimize leakage currents and reduce flickering. This semiconductor layer is distinct from the driving thin film transistor's layer, allowing selective treatment and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a conventional thin film transistor is used for displaying still images at low frequencies, then the display device can operate at low frequencies, but significant leakage currents occur causing flickering and brightness instability
Solution Approach 1:
The patent applies different treatments to different regions of the semiconductor layer. Specifically, the channel region undergoes hydrogen plasma treatment to increase hydrogen concentration and reduce grain boundary trap density, while the source and drain regions are treated with excimer laser annealing to optimize their electrical properties. This localized differentiation of treatment methods resolves the contradiction by optimizing each region for its specific function while collectively reducing leakage current.
Solution Approach 2:
The patent changes key parameters of the semiconductor layer including hydrogen concentration (increased in channel region), grain boundary trap density (reduced in channel region), and crystalline structure (optimized through laser annealing). These parameter changes transform the semiconductor layer properties to achieve lower leakage current while maintaining low-frequency operation capability.
2Reliability
If the semiconductor layer is treated to reduce leakage current, then flickering is minimized, but the manufacturing process becomes more complex
Solution Approach 1:
The patent incorporates hydrogen plasma treatment and excimer laser annealing as preliminary steps during the semiconductor layer formation process. By integrating these treatments into the manufacturing flow before final device assembly, the complex treatments are performed when the semiconductor layer is most accessible and can be optimized without requiring additional post-processing steps.
Solution Approach 2:
The patent replaces traditional thermal annealing processes with excimer laser annealing, which uses optical energy instead of conventional thermal fields. This substitution allows for more precise and localized treatment of the semiconductor layer, reducing the need for complex thermal management systems and enabling better control over the treatment parameters.
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 reduces leakage currents in the compensation transistor, minimizing screen flickering and allowing for stable image display at low frequencies with minimal brightness changes, thus enhancing the display's performance and user experience.
Implementation Method 1
A portion of the third semiconductor layer may be hydrogen-plasma treated
Implementation Method 2
A hydrogen concentration of a portion of the third semiconductor layer may be greater than a hydrogen concentration of the first semiconductor layer
Implementation Method 3
A portion of the third semiconductor layer may be crystallized by performing excimer laser-annealing a plurality of times
Implementation Method 4
A portion of the third semiconductor layer may be crystallized by performing excimer laser-annealing a plurality of times
Data Source
AI summary
A display device including: a first thin film transistor (TFT) including a first semiconductor layer and a first gate electrode, the first semiconductor layer including a first channel region, a first source region, and a first drain region; a third TFT including a third semiconductor layer and a third gate electrode, the third semiconductor layer including a third channel region, a third source region, and a third drain region, wherein a leakage current of the third TFT in an off-state is less than a leakage current of the first TFT in an off-state; and a pixel electrode connected to one of the first source region and the first drain region, wherein the one of the first source region and the first drain region is connected to the third TFT.