Oxide Semiconductor Transistor Crystallinity Stabilization
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Solution Overview
Problem
The electric characteristics of transistors using oxide semiconductor films are unstable due to the amorphous state of the gate-electrode-side interface and are affected by temperature and light irradiation, making them unsuitable for large-scale production on glass substrates.
Innovation Solution
Forming a region with high crystallinity at the interface between the oxide semiconductor film and the gate insulating film by using a second crystal structure, such as wurtzite, and performing heat treatment to achieve c-axis alignment and high crystallinity, thereby stabilizing the electric characteristics and enabling mass production on large substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an oxide semiconductor film is used as the active layer, then the transistor can be formed over a larger glass substrate, but the electric characteristics become unstable due to the amorphous state of the interface
Solution Approach 1:
The patent applies local quality by creating a crystalline region specifically at the interface between the oxide semiconductor film and gate insulating film, while the rest of the oxide semiconductor film can remain in its original state. This localized crystallization at the critical interface region improves electric characteristic stability without requiring the entire film to be crystalline, thus maintaining compatibility with large substrate fabrication.
Solution Approach 2:
The patent employs preliminary action by performing heat treatment before final device completion to pre-crystallize the interface region. This preliminary crystallization step prepares the critical interface area in advance, ensuring stable electric characteristics before subsequent manufacturing steps are completed.
2Ease of manufacture
If the interface is in an amorphous state, then the manufacturing process is simpler, but the electric characteristics are easily changed by temperature and light irradiation
Solution Approach 1:
The patent applies local quality by creating a crystalline region specifically at the interface between the oxide semiconductor film and gate insulating film, while the rest of the oxide semiconductor film can remain in its original state. This localized crystallization at the critical interface region improves electric characteristic stability without requiring the entire film to be crystalline, thus maintaining compatibility with large substrate fabrication.
Solution Approach 2:
The patent employs parameter changes by applying heat treatment to transform the interface region from amorphous to crystalline state. This controlled parameter change (temperature application) modifies the physical state of the interface region to improve stability against temperature and light irradiation effects.
3Reliability
If a crystalline structure is formed at the interface, then the electric characteristics become stable, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies local quality by creating a crystalline region specifically at the interface between the oxide semiconductor film and gate insulating film, while the rest of the oxide semiconductor film can remain in its original state. This localized crystallization at the critical interface region improves electric characteristic stability without requiring the entire film to be crystalline, thus maintaining compatibility with large substrate fabrication.
Solution Approach 2:
The patent employs self-service by utilizing the heat treatment process already present in the manufacturing workflow to simultaneously achieve crystallization of the interface region. The existing thermal processing steps serve dual purposes: completing the manufacturing process and inducing the desired crystalline structure at the interface.
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
The solution results in a highly reliable transistor with stable electric characteristics, reduced threshold voltage shift under light irradiation or bias-temperature stress, and facilitates mass production on large substrates.
Implementation Method 1
performing heat treatment to achieve c-axis alignment and high crystallinity
Implementation Method 2
forming a region with high crystallinity at the interface between the oxide semiconductor film and the gate insulating film
Data Source
AI summary
A highly reliable semiconductor device is manufactured by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. An oxide semiconductor film which can have a first crystal structure by heat treatment and an oxide semiconductor film which can have a second crystal structure by heat treatment are formed so as to be stacked, and then heat treatment is performed; accordingly, crystal growth occurs with the use of an oxide semiconductor film having the second crystal structure as a seed, so that an oxide semiconductor film having the first crystal structure is formed. An oxide semiconductor film formed in this manner is used for an active layer of the transistor.