Oxide TFT Substrate Layout for Low Leakage and Reliability
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Solution Overview
Problem
Existing thin-film transistor (TFT) technologies face challenges in achieving lower power consumption, smaller circuit size, and higher reliability, particularly with oxide semiconductor materials that exhibit low leakage current but often have reliability issues due to high mobility leading to degradation in characteristics.
Innovation Solution
The implementation of a thin-film transistor substrate with multiple oxide semiconductor regions having different characteristics, where one region's low-resistive area extends to serve as a bottom-gate electrode for another TFT, reducing contact holes and enhancing reliability, and employing materials like ITZO, IGZTO, and IGZO with varying mobility and bandgap to optimize performance based on circuit function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If oxide semiconductor materials with high mobility are used to achieve low leakage current, then power consumption is reduced, but reliability deteriorates due to degradation in characteristics
Solution Approach 1:
The patent applies local quality by creating different oxide semiconductor films with distinct properties: a first oxide semiconductor film with high mobility for low leakage current, and a second oxide semiconductor film with appropriate mobility for stability. Each film is positioned in specific regions to optimize both power consumption and reliability locally throughout the device structure.
Solution Approach 2:
The patent uses composite materials by combining multiple oxide semiconductor films with different compositions and properties (such as IGZO, ITZO, IGZTO) in a layered structure. This composite approach allows the device to simultaneously achieve low leakage current from high-mobility regions and stability from other regions, resolving the contradiction between power consumption and reliability.
2Reliability
If multiple oxide semiconductor films with different properties are used to optimize performance, then reliability and power consumption improve, but device complexity increases
Solution Approach 1:
The patent merges multiple oxide semiconductor films into an integrated layered structure where the first and second oxide semiconductor films are stacked and interconnected. This combining approach allows the complex multi-film structure to function as a unified device component, achieving improved reliability while managing complexity through systematic integration rather than separate discrete components.
Solution Approach 2:
The patent implements multi-functionality by designing the oxide semiconductor films to serve multiple purposes: the first oxide semiconductor film provides low leakage current while also serving as a functional layer in the stacked structure, and the second oxide semiconductor film provides stability while contributing to the overall device architecture. This multi-functional design reduces the need for additional separate components.
3Ease of manufacture
If the low-resistive region extends to serve as bottom-gate electrode, then contact holes are reduced and manufacturing is simplified, but the structure becomes more complex
Solution Approach 1:
The patent merges the low-resistive region with the bottom-gate electrode function by extending the low-resistive region to serve dual purposes: as part of the source/drain structure and as the bottom-gate electrode for the second TFT. This merging eliminates the need for separate contact holes and additional electrode structures, simplifying manufacturing while the resulting integrated structure provides the necessary complexity for enhanced device performance.
Data Source
AI summary
A thin-film transistor substrate includes a first oxide semiconductor film, a second oxide semiconductor film located upper than the first oxide semiconductor film, a first insulating film located lower than the second oxide semiconductor film and covering the first oxide semiconductor film. The first oxide semiconductor film includes first and second low-resistive regions, and a channel region. Each of the first and second low-resistive regions includes a source/drain region. The second oxide semiconductor film includes third and fourth low-resistive regions, and a channel region of a second thin-film transistor. Each of the third and fourth low-resistive regions includes a source/drain region of the second thin-film transistor. A part of the first low-resistive region extending from a source/drain region of the first thin-film transistor is a bottom-gate electrode of the second thin-film transistor.