Indium Concentration Gradient in Oxide Semiconductor Transistors
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Solution Overview
Problem
In transistors using oxide semiconductors, the interface between the oxide semiconductor film and the insulating film is unstable, leading to poor reliability due to indium diffusion, which increases leakage current and affects the transistor's electric characteristics.
Innovation Solution
The concentration of indium is reduced at the surface of the oxide semiconductor film, forming a layer that does not contain indium, which is used as part of the insulating film to improve the interface characteristics, and a concentration gradient is created by exposing the film to a reducing atmosphere, such as silane or hydrogen, to prevent indium diffusion into the insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon oxide film is used as the gate insulating film in a transistor formed using an oxide semiconductor, then the manufacturing process is simplified and compatibility is improved, but the interface characteristics become unstable and reliability deteriorates due to indium diffusion
Solution Approach 1:
The oxide semiconductor film is designed with non-uniform indium concentration distribution, creating an indium-poor region at the interface with the gate insulating film and an indium-rich region in the bulk. This local variation in composition prevents indium diffusion into the gate insulating film while maintaining the desired semiconductor properties in the active region
Solution Approach 2:
An oxygen-rich layer is formed at the interface between the oxide semiconductor film and the gate insulating film. This intermediate layer acts as a barrier that prevents indium atoms from diffusing into the silicon oxide gate insulating film, thereby stabilizing the interface characteristics
2Productivity
If indium concentration is maintained uniformly high throughout the oxide semiconductor film, then the semiconductor properties are optimized, but indium diffusion into the gate insulating film increases causing leakage current
Solution Approach 1:
The oxide semiconductor film is designed with non-uniform indium concentration distribution, creating an indium-poor region at the interface with the gate insulating film and an indium-rich region in the bulk. This local variation in composition prevents indium diffusion into the gate insulating film while maintaining the desired semiconductor properties in the active region
Solution Approach 2:
Indium is selectively removed or prevented from being present in the interface region between the oxide semiconductor film and the gate insulating film. This extraction of indium from the critical interface zone eliminates the source of diffusion while preserving indium in the bulk for maintaining semiconductor properties
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 stabilizes the electric characteristics and enhances the reliability of the transistor by reducing indium diffusion and improving the interface between the oxide semiconductor and insulating films, thereby minimizing leakage current.
Implementation Method 1
the concentration of indium at a surface of the oxide semiconductor film is decreased, whereby diffusion of indium into an insulating film which is formed on and in contact with the oxide semiconductor film is prevented
Data Source
AI summary
A highly reliable semiconductor device having stable electric characteristics is provided by suppressing, in a transistor including an oxide semiconductor film, diffusion of indium into an insulating film in contact with the oxide semiconductor film and improving the characteristics of the interface between the oxide semiconductor film and the insulating film. In an oxide semiconductor film containing indium, the indium concentration at a surface is decreased, thereby preventing diffusion of indium into an insulating film on and in contact with the oxide semiconductor film. By decreasing the indium concentration at the surface of the oxide semiconductor film, a layer which does not substantially contain indium can be formed at the surface. By using this layer as part of the insulating film, the characteristics of the interface between the oxide semiconductor film and the insulating film in contact with the oxide semiconductor film are improved.