CAAC-OS Film C-Axis Alignment for Oxygen Defect Reduction
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Solution Overview
Problem
Semiconductor devices face reliability issues due to variations in electric characteristics, particularly in the channel formation region, which are influenced by the stability of the semiconductor film to heat and light, and are exacerbated by defects such as oxygen defects in amorphous oxide semiconductor films.
Innovation Solution
A c-axis aligned crystalline oxide semiconductor (CAAC-OS) film with a crystal part whose c-axis is substantially perpendicular to the surface, containing indium, gallium, and zinc, is used in the channel formation region, which has a longer crystal arrangement length and reduced oxygen defects, enhancing stability and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an amorphous oxide semiconductor film is used in the channel formation region, then the manufacturing process is simpler, but the stability to heat and light is poor causing variation in electric characteristics
Solution Approach 1:
The invention changes the structural parameter of the oxide semiconductor film from amorphous to c-axis aligned crystalline structure. This parameter change fundamentally improves the stability to heat and light while maintaining the semiconductor functionality, resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The invention uses a composite structure where the oxide semiconductor film is formed over an aluminum oxide film layer. This composite material approach provides both the semiconductor properties needed for device operation and the thermal stability required for reliable performance, addressing the contradiction between manufacturing simplicity and heat stability.
2Ease of manufacture
If an amorphous oxide semiconductor film is used in the channel formation region, then the manufacturing process is simpler, but oxygen defects occur causing variation in electric characteristics
Solution Approach 1:
The invention changes the structural parameter from amorphous to c-axis aligned crystalline structure, which inherently reduces oxygen defects. This parameter change improves manufacturing precision regarding defect control while the manufacturing process remains relatively straightforward.
Solution Approach 2:
The aluminum oxide film serves as an intermediary layer between the substrate and the oxide semiconductor film. This intermediary layer prevents oxygen deficiency and reduces oxygen defects in the semiconductor film, improving manufacturing precision without significantly complicating the manufacturing process.
3Stability of the object's composition
If the crystal arrangement length in the oxide semiconductor film is increased, then the stability to heat and light is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention optimizes the crystal arrangement length parameter to be 1.5 nm or more, which provides sufficient stability to heat and light. By setting a specific threshold value for this parameter, the invention achieves high stability while avoiding the need for excessively complex crystal structure control.
Solution Approach 2:
The oxide semiconductor film has a natural tendency to form a c-axis aligned crystalline structure under appropriate deposition conditions. This self-organizing property reduces the manufacturing complexity required to achieve the desired crystal arrangement length, as the structure forms spontaneously rather than requiring complex external control mechanisms.
4Reliability
If the oxide semiconductor film has high crystal arrangement length, then the electric conductivity is stable, but the manufacturing precision requirements increase
Solution Approach 1:
The invention changes the crystalline structure parameter to c-axis aligned, which naturally provides stable electric conductivity. This parameter change achieves reliable electrical performance while the manufacturing precision requirements are managed through controlled deposition processes rather than extremely tight tolerances.
Solution Approach 2:
The invention requires c-axis alignment specifically in the region that will form the channel, while other regions of the film can have less stringent requirements. This local quality approach ensures stable electric conductivity where needed without requiring uniform high precision throughout the entire film, reducing overall manufacturing precision requirements.
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 CAAC-OS film exhibits high stability to heat and light, reduces oxygen defects, and maintains stable electric conductivity, leading to a highly reliable semiconductor device with minimal variation in electric characteristics.
Implementation Method 1
an oxide semiconductor film which includes a crystal part whose c-axis is substantially perpendicular to a surface of the oxide semiconductor film
Data Source
AI summary
To provide an oxide semiconductor film which has high stability and does not easily cause variation in electric characteristics of a transistor, a transistor including the oxide semiconductor film in its channel formation region, and a highly reliable semiconductor device including the transistor. The oxide semiconductor film including indium includes a crystal part whose c-axis is substantially perpendicular to a surface of the oxide semiconductor film. In the crystal part, the length of a crystal arrangement part containing indium and oxygen on a plane perpendicular to the c-axis is more than 1.5 nm. Further, the semiconductor device includes the transistor including the oxide semiconductor film in its channel formation region.