Thin Film Transistor Gate Insulating Film End Face Protection
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Solution Overview
Problem
Oxide semiconductors used in thin film transistors are prone to instability due to moisture and hydrogen infiltration, leading to unreliable electrical characteristics.
Innovation Solution
A thin film transistor design where the end faces of the gate insulating film are covered with source-drain electrodes or a protection film, preventing moisture and hydrogen intrusion and stabilizing the oxide semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide semiconductor is used as the active layer to achieve high electron mobility, then electrical characteristics are improved, but the transistor becomes sensitive to moisture and hydrogen infiltration causing unstable characteristics
Solution Approach 1:
A protective film is introduced as an intermediary layer between the oxide semiconductor layer and the external environment. This protective film acts as a barrier that prevents moisture and hydrogen from reaching the oxide semiconductor, thereby eliminating the harmful effects of infiltration while preserving the high electron mobility characteristics of the oxide semiconductor material.
Solution Approach 2:
The protective film creates an inert environment around the oxide semiconductor layer by forming a hermetic seal that excludes moisture and hydrogen. This inert atmosphere prevents chemical reactions and degradation of the oxide semiconductor, ensuring stable TFT characteristics over time.
2Ease of manufacture
If the gate insulating film end faces are left exposed to simplify manufacturing, then manufacturing complexity is reduced, but moisture and hydrogen can infiltrate causing device degradation
Solution Approach 1:
The protective film is extended to cover not only the oxide semiconductor layer but also the end faces of the gate insulating film. By merging the protection function across multiple surfaces, the design achieves comprehensive coverage without adding separate protective structures for the gate insulating film ends, thus maintaining manufacturing simplicity while enhancing device stability.
Data Source
AI summary
A thin film transistor includes: a gate electrode and a pair of source-drain electrodes provided on a substrate; an oxide semiconductor layer provided between the gate electrode and the pair of source-drain electrodes, the oxide semiconductor layer forming a channel; a protection film provided over whole of a surface above the substrate; and a gate insulating film provided on a gate electrode side of the oxide semiconductor layer, the gate insulating film having end faces part or all of which are covered with the pair of source-drain electrodes or with the protection film.