Oxide Semiconductor TFT Oxygen Supply via SiO and AlOx Layers
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Solution Overview
Problem
In oxide semiconductor TFTs, a leak current increases due to deoxidization, where oxygens are extracted by metal or hydrogens are supplied from insulating layers, leading to reduced channel resistance and increased leak current.
Innovation Solution
A silicon oxide film is used as the first insulating layer, which is oxygen-rich to supply oxygens to the oxide semiconductor. An aluminum oxide film is then deposited on top of the silicon oxide film to confine the oxygens, ensuring they are efficiently supplied to the oxide semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oxygen-rich SiO film is used to supply oxygens to the oxide semiconductor, then deoxidization is suppressed, but the SiO film cannot maintain enough insulating characteristics due to defects
Solution Approach 1:
The patent uses a composite structure consisting of a SiO film and an AlOx film. The SiO film provides oxygen supply to the oxide semiconductor, while the AlOx film layer compensates for the defects in the SiO film and maintains insulating characteristics. This composite material approach allows both functions to coexist without compromising either deoxidization suppression or insulating performance.
2Reliability
If oxygens are supplied from the SiO film to the oxide semiconductor, then leak current is reduced, but oxygens may escape to other portions and insufficient oxygens remain in the SiO film
Solution Approach 1:
The AlOx film acts as an intermediary layer between the SiO film and the external environment. It prevents oxygen escape to other portions while allowing controlled oxygen supply to the oxide semiconductor. The AlOx film mediates the oxygen distribution, ensuring that sufficient oxygen remains in the SiO film to maintain low leak current characteristics.
3Reliability
If the resistance of the oxide semiconductor at the channel decreases due to deoxidization, then conductivity increases, but leak current increases
Solution Approach 1:
The patent applies preliminary anti-action by forming the oxygen-rich SiO film and AlOx film structure before the oxide semiconductor is fully formed and before any deoxidization can occur. This pre-configured oxygen supply system prevents deoxidization from happening in the first place, thereby preventing the harmful increase in leak current while allowing the oxide semiconductor to maintain its proper resistance characteristics for reliable TFT switching.
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
This configuration effectively suppresses deoxidization of the oxide semiconductor, resulting in a low leak current and stable characteristics of the TFT, while maintaining sufficient insulating properties.
Implementation Method 1
the aluminum oxide film is formed on the silicon oxide film; oxygens in the silicon oxide film are effectively confined in the silicon oxide film by the aluminum oxide film
Implementation Method 2
oxygens in the first insulating film are efficiently supplied to the oxide semiconductor layer
Data Source
AI summary
The purpose of the invention is to form a stable oxide semiconductor TFT in a display device. The concrete structure is: A display device having a TFT substrate that includes a TFT having an oxide semiconductor layer comprising: the oxide semiconductor layer is formed on a first insulating film that is formed by a silicon oxide layer, the oxide semiconductor layer and an aluminum oxide film are directly formed on the first insulating film. The first insulating film becomes oxygen rich when the aluminum oxide film is formed on the first insulating film by sputtering. Oxygens in the first insulating film is effectively confined in the first insulating film, eventually, the oxygens diffuse to the oxide semiconductor for a stable operation of the oxide semiconductor TFT.