Thin Film Transistor Dual Gate Insulator Structure
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Solution Overview
Problem
Existing thin film transistors experience characteristic degradation in mobility and S value due to defects and surface issues during manufacturing, which affects their performance and reliability.
Innovation Solution
A thin film transistor configuration that includes a semiconductor layer covered by a first gate insulating film and a second gate insulating film extending across opposite sides, with a gate electrode facing the semiconductor layer through the second insulating film, which protects the surface and prevents defects during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thin film transistor structure is used, then the device complexity is low, but the reliability deteriorates due to characteristic degradation in mobility and S value
Solution Approach 1:
The gate insulating film is divided into multiple layers: a first gate insulating film in contact with the semiconductor layer, and a second gate insulating film covering the first gate insulating film. This segmentation allows each layer to perform specific functions - the first layer provides interface quality while the second layer provides protection and electrical isolation, thereby improving reliability without excessive complexity
Solution Approach 2:
The first gate insulating film acts as an intermediary layer between the semiconductor layer and the second gate insulating film. This intermediate layer protects the semiconductor layer surface from defects during manufacturing while maintaining electrical characteristics, thus improving reliability
2Manufacturing precision
If the semiconductor layer surface is exposed during manufacturing, then the ease of manufacture is high, but the manufacturing precision deteriorates due to surface defects
Solution Approach 1:
The first gate insulating film is formed to cover the semiconductor layer surface before subsequent manufacturing steps. This preliminary protective action prevents surface defects from occurring during later processing steps, thereby improving manufacturing precision without significantly complicating the overall manufacturing process
Solution Approach 2:
The gate insulating film structure provides beforehand protection to the semiconductor layer surface, cushioning it against potential damage and contamination during manufacturing. This prior cushioning ensures high surface quality and prevents defects before they can occur
3Reliability
If mobility and S value are improved through better surface protection, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The gate insulating film structure provides localized quality improvement at the semiconductor layer interface through the first gate insulating film, while the second gate insulating film provides localized protection. This local quality approach improves mobility and S value without requiring complex modifications throughout the entire device structure
Data Source
AI summary
A thin film transistor includes a substrate, a semiconductor layer, a first gate insulating film, a second gate insulating film, and a gate electrode. The semiconductor layer is provided in a selective region of the substrate. The first gate insulating film is provided in the selective region of the substrate and covers a surface of the semiconductor layer. The second gate insulating film extends across opposite sides of the first gate insulating film along a channel width direction and covers the first gate insulating film that covers the semiconductor layer. The gate electrode faces the semiconductor layer across the second gate insulating film.