Mixed Gate Oxide TFT Display Resolving Adaptability Complexity Trade-off
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Solution Overview
Problem
Existing display apparatuses face challenges in effectively integrating bottom gate and top gate type thin film transistors with different properties, which are necessary for high-performance and high-resolution displays, due to differences in required properties for switching and driving transistors.
Innovation Solution
A display apparatus comprising a pixel driving circuit with both a bottom gate type and a top gate type thin film transistor, where the first thin film transistor has a lower s-factor value for switching and the second thin film transistor has a higher s-factor value for driving, both utilizing oxide semiconductor materials and structured to maintain optimal electrical properties and manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single type of thin film transistor is used in the display apparatus, then the device complexity is reduced, but the performance and resolution cannot be optimized for different functions
Solution Approach 1:
The pixel driving circuit is segmented into different functional units with different transistor types: switching transistors use bottom gate type TFTs while driving transistors use top gate type TFTs. This segmentation allows each transistor type to be optimized for its specific function, with bottom gate transistors providing good switching characteristics and top gate transistors providing good driving characteristics, thereby resolving the contradiction between functional adaptability and device complexity.
Solution Approach 2:
Different regions of the display apparatus are assigned different transistor types based on local functional requirements. The switching transistor region uses bottom gate type TFTs with optimized gate insulating film structures for switching performance, while the driving transistor region uses top gate type TFTs with optimized channel structures for driving performance. This local quality approach allows each region to have the transistor structure best suited to its specific function.
2Ease of manufacture
If oxide semiconductor material is used in all thin film transistors, then manufacturing cost is reduced and transparency is improved, but the s-factor values cannot be differentiated for optimal switching and driving performance
Solution Approach 1:
While using oxide semiconductor material uniformly across all transistors to maintain manufacturing simplicity and cost-effectiveness, the patent differentiates s-factor values by changing structural parameters: bottom gate type transistors have gate insulating film thickness and composition optimized for low s-factor switching performance, while top gate type transistors have channel layer thickness and gate structure optimized for different s-factor driving performance. This parameter change approach allows s-factor differentiation without compromising manufacturing ease.
3Manufacturing precision
If high-density integration of thin film transistors is implemented, then display resolution is improved, but the different properties of switching and driving transistors cannot be effectively disposed
Solution Approach 1:
The patent resolves the density-adaptability contradiction by utilizing vertical dimensionality: bottom gate type transistors have the gate electrode positioned below the active layer, while top gate type transistors have the gate electrode positioned above the active layer. This dimensional differentiation allows both transistor types to be integrated in the same planar space without interfering with each other's electric fields, enabling high-density integration while maintaining distinct functional properties for switching and driving operations.
Data Source
AI summary
A display apparatus can include a first thin film transistor and a second thin film transistor, the first thin film transistor has a bottom gate structure, the second thin film transistor has a top gate structure, and an s-factor value of the first thin film transistor is smaller than an s-factor value of the second thin film transistor.