Semiconductor Device Design for Stable Electrical Characteristics
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Summary
Problems
Transistors with oxide semiconductor films face unstable electrical characteristics due to oxygen deficiency, particularly after bias-temperature stress tests or light irradiation, which affects their reliability.
Innovation solutions
A semiconductor device structure is developed with a first oxide semiconductor film having a lower indium content and higher gallium content than a second oxide semiconductor film, where the first film suppresses oxygen release from an underlying oxide film during the second film's formation, allowing oxygen to be supplied to the second film, thereby stabilizing its electrical characteristics.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If an oxide semiconductor film is formed directly over an oxide film, then the manufacturing process is simple, but oxygen deficiency occurs in the oxide semiconductor film leading to unstable electrical characteristics
Why choose this principle:
The oxide semiconductor film is divided into two distinct layers: a first oxide semiconductor film with lower In/Ga ratio formed directly on the oxide film, and a second oxide semiconductor film with higher In/Ga ratio formed on the first film. This segmentation allows each layer to serve different functions – the first layer suppresses oxygen release from the oxide film, while the second layer receives oxygen supply to prevent oxygen deficiency, thus resolving the contradiction between manufacturing simplicity and electrical stability.
Principle concept:
If an oxide semiconductor film is formed directly over an oxide film, then the manufacturing process is simple, but oxygen deficiency occurs in the oxide semiconductor film leading to unstable electrical characteristics
Why choose this principle:
The first oxide semiconductor film acts as an intermediary layer between the oxide film and the second oxide semiconductor film. It mediates the oxygen release process by suppressing oxygen release from the oxide film during the formation of the second film, while still allowing oxygen to be supplied to the second film, thereby preventing oxygen deficiency and ensuring stable electrical characteristics.
Application Domain
Data Source
AI summary:
A semiconductor device structure is developed with a first oxide semiconductor film having a lower indium content and higher gallium content than a second oxide semiconductor film, where the first film suppresses oxygen release from an underlying oxide film during the second film's formation, allowing oxygen to be supplied to the second film, thereby stabilizing its electrical characteristics.
Abstract
Provided is a transistor which includes an oxide semiconductor film and has stable electrical characteristics. In the transistor, over an oxide film which can release oxygen by being heated, a first oxide semiconductor film which can suppress oxygen release at least from the oxide film is formed. Over the first oxide semiconductor film, a second oxide semiconductor film is formed. With such a structure in which the oxide semiconductor films are stacked, the oxygen release from the oxide film can be suppressed at the time of the formation of the second oxide semiconductor film, and oxygen can be released from the oxide film in later-performed heat treatment. Thus, oxygen can pass through the first oxide semiconductor film to be favorably supplied to the second oxide semiconductor film. Oxygen supplied to the second oxide semiconductor film can suppress the generation of oxygen deficiency, resulting in stable electrical characteristics.