Oxide Semiconductor Transistor Gate Insulator Hydrogen Management
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Solution Overview
Problem
Transistors using oxide semiconductors face challenges in controlling threshold voltage due to hydrogen diffusion, leading to unstable electric characteristics and high off-state current, particularly when formed on larger substrates like glass.
Innovation Solution
Incorporating a hydrogen capture film and a hydrogen permeable film in the gate insulating structure of the transistor, where the hydrogen permeable film is between the oxide semiconductor film and the hydrogen capture film, allowing hydrogen to be transferred through heat treatment, thereby reducing hydrogen concentration near the interface and stabilizing electric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor is formed using oxide semiconductor film, then high field-effect mobility can be achieved, but hydrogen diffusion into the oxide semiconductor film causes threshold voltage shift and unstable electric characteristics
Solution Approach 1:
A hydrogen barrier film is introduced as an intermediary layer between the oxide semiconductor film and the gate insulating film. This barrier film prevents hydrogen from diffusing into the oxide semiconductor film from the gate insulating film, thereby maintaining stable electric characteristics and preventing threshold voltage shift.
Solution Approach 2:
The harmful hydrogen is extracted or blocked from reaching the oxide semiconductor film by the hydrogen barrier film. The barrier film selectively prevents hydrogen diffusion while allowing the transistor to function normally, thus removing the harmful effect without compromising the device operation.
2Reliability
If hydrogen concentration in oxide semiconductor film is reduced, then off-state current is reduced and electric characteristics are stabilized, but completely removing hydrogen is difficult
Solution Approach 1:
The hydrogen barrier film serves as a mediator that blocks the path of hydrogen diffusion. By placing this barrier between the hydrogen source (gate insulating film) and the oxide semiconductor film, hydrogen concentration in the oxide semiconductor is reduced without requiring complete removal of all hydrogen sources from the system.
3Area of stationary object
If transistor is formed on larger glass substrate, then device area is increased, but controlling hydrogen diffusion becomes more difficult leading to unstable characteristics
Solution Approach 1:
The gate insulating film is segmented into multiple layers, including a hydrogen barrier film layer and a gate insulating film layer. This segmentation allows different regions of the insulating structure to perform different functions: the barrier film prevents hydrogen diffusion while the gate insulating film provides electrical insulation, ensuring uniform characteristics across large substrates.
Solution Approach 2:
The hydrogen barrier film acts as a mediator that uniformly prevents hydrogen diffusion across the entire large substrate area. This ensures consistent electric characteristics throughout the device, even when manufactured on large glass substrates where uniformity would otherwise be difficult to maintain.
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 approach results in a highly reliable semiconductor device with reduced off-state current and stable electric characteristics, enabling improved performance and reliability of transistors, especially for larger substrate applications.
Implementation Method 1
hydrogen is transferred from the oxide semiconductor film to the hydrogen capture film through the hydrogen permeable film by heat treatment
Implementation Method 2
a film for capturing or absorbing hydrogen from the oxide semiconductor film (a hydrogen capture film or a hydrogen absorption film)
Data Source
AI summary
In the transistor including an oxide semiconductor film, a gate insulating film of the transistor including an oxide semiconductor film has a stacked-layer structure of the hydrogen capture film and the hydrogen permeable film. At this time, the hydrogen permeable film is formed on a side which is in contact with the oxide semiconductor film, and the hydrogen capture film is formed on a side which is in contact with a gate electrode. After that, hydrogen released from the oxide semiconductor film is transferred to the hydrogen capture film through the hydrogen permeable film by the heat treatment.