Stacked TFT Display Layout for Low Current Variation and Drive
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Solution Overview
Problem
Current thin film transistors in display devices face challenges with high current variation and limited drive performance, particularly due to shot variation in laser annealing of low-temperature polysilicon and the inability to meet narrow frame and low power consumption requirements with oxide semiconductor processes.
Innovation Solution
A display device design incorporating staggered thin film transistors with a low-temperature polysilicon channel layer in the peripheral region and an oxide semiconductor channel layer in the display region, where the oxide semiconductor transistors are formed above the polysilicon transistors to minimize parasitic capacitance and heat effects, enhancing drive performance and reducing current variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low-temperature polysilicon thin film transistors are used, then drive performance is improved, but current variation increases and shot variation becomes large
Solution Approach 1:
The patent applies different channel layer materials in different regions: low-temperature polysilicon in the peripheral region for high drive performance, and oxide semiconductor in the display region for low current variation. This local differentiation resolves the contradiction by optimizing each region for its specific functional requirements.
2Manufacturing precision
If oxide semiconductor thin film transistors are used, then current variation decreases, but narrow frame and low power consumption requirements are not satisfied
Solution Approach 1:
The patent assigns oxide semiconductor thin film transistors specifically to the display region where low current variation is critical for pixel uniformity, while using low-temperature polysilicon in the peripheral region where high drive performance is needed for circuit operation. This spatial differentiation resolves the contradiction between current variation and drive performance.
3Manufacturing precision
If laser irradiation is applied to reduce current variation, then shot variation decreases, but device cost and material cost increase
Solution Approach 1:
The patent replaces the expensive laser irradiation process with a material-based solution using oxide semiconductor thin film transistors in the display region. The oxide semiconductor material inherently provides low current variation without requiring additional costly processing steps, thus resolving the contradiction between manufacturing precision and ease of manufacture.
4Reliability
If staggered thin film transistors are used, then parasitic capacitance decreases and drive performance increases, but heat impact may affect oxide semiconductor transistors during low-temperature polysilicon formation
Solution Approach 1:
The patent segments the transistor structure into two types: staggered configuration in the peripheral region for high drive performance, and a modified configuration in the display region for oxide semiconductor transistors that avoids heat impact. This segmentation allows each region to optimize for its specific requirements while mitigating the harmful heat effect on oxide semiconductors.
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 achieves high drive performance and reduced current variation by minimizing parasitic capacitance and avoiding heat effects during the formation of the oxide semiconductor transistors, while also addressing the limitations of existing thin film transistor processes.
Implementation Method 1
The silicon is polycrystallized by excimer laser annealing
Data Source
AI summary
A plurality of thin film transistors provided in a peripheral region are first staggered thin film transistors where a first channel layer configured of low-temperature polysilicon is included, and the first channel layer is not interposed between a first source electrode and a first gate electrode, and between a first drain electrode and the first gate electrode. A plurality of thin film transistors provided in a display region are second staggered thin film transistors where a second channel layer configured of an oxide semiconductor is included, and the second channel layer is not interposed between a second source electrode and a second gate electrode, and between a second drain electrode and the second gate electrode. The first thin film transistor is located below the second thin film transistor.