Corundum Crystal Semiconductor Insulating Films
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Solution Overview
Problem
SiC and GaN semiconductor devices face challenges in achieving a normally-off device structure due to difficulties in forming high-quality insulating films, particularly with SiC-MOSFETs, where the formation of a semiconductor layer with good crystallinity leads to issues with the insulating film's viability and electron accumulation.
Innovation Solution
The use of materials with a corundum crystal structure for the base substrate, semiconductor layer, and insulating film, such as aluminum gallium oxide, indium oxide, and sapphire, which are grown using CVD, to prevent electron accumulation and current leakage by minimizing lattice constant mismatch and polarization differences, allowing for the formation of high-quality films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor layer with good crystallinity is formed on SiC substrate, then device characteristics are improved, but electron accumulation occurs at the interface with insulating film
Solution Approach 1:
The invention changes the crystal structure parameter from conventional cubic or zinc blende structure to corundum crystal structure for the insulating film. This structural parameter change eliminates the polarity that causes electron accumulation, while maintaining good interface characteristics with the semiconductor layer.
Solution Approach 2:
The invention uses a composite structure where the insulating film is formed by corundum-type oxide materials (such as aluminum oxide, gallium oxide, or their mixed crystals) that combine both insulating properties and lattice matching characteristics with SiC, preventing electron accumulation while maintaining device performance.
2Ease of manufacture
If thermal oxidation is used to form insulating film, then film formation is viable, but good quality insulating film cannot be achieved on SiC-MOSFET
Solution Approach 1:
The invention changes the material composition parameter of the insulating film from conventional silicon oxide to corundum-type oxide materials. This parameter change enables the formation of high-quality insulating films with excellent interface characteristics that are suitable for SiC-MOSFET applications.
Solution Approach 2:
The invention introduces corundum-type oxide materials as an intermediary layer between the SiC semiconductor and the gate structure. This intermediary material provides both good interface quality and high insulating properties, resolving the contradiction between manufacturability and film quality.
3Adaptability or versatility
If dissimilar materials are used at interfaces, then device functionality is achieved, but current leakage occurs in lateral devices
Solution Approach 1:
The invention applies homogeneity principle by using corundum crystal structure throughout the insulating film and interface regions. This uniform crystal structure eliminates polarization differences at interfaces, preventing current leakage while maintaining device functionality.
Solution Approach 2:
The invention changes the crystal structure parameter of the insulating film to corundum type, which has extremely small polarization in directions perpendicular to the c-axis. This parameter change eliminates the harmful polarization effects at interfaces that cause current leakage in lateral devices.
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 enables the creation of semiconductor devices with improved insulating films that prevent electron accumulation and current leakage, facilitating the development of reliable, high-performance power semiconductor devices with a normally-off operation.
Implementation Method 1
Materials having a corundum crystal structure are known to have extremely small polarization in a direction perpendicular to c-axis, such as the m-axis direction or α-axis direction. This prevents accumulation of electrons at the dissimilar material interfaces
Implementation Method 2
The base substrate, the semiconductor layer, and the insulating film having a corundum crystal structure are formed through crystal growth by means of CVD or the like
Data Source
AI summary
There is provided a semiconductor device including corundum crystal films of good quality. There is provided a semiconductor device including a base substrate, a semiconductor layer, and an insulating film each having a corundum crystal structure. Materials having a corundum crystal structure include many types of oxide films capable of functioning as an insulating film. Since all the base substrate, the semiconductor layer, and the insulating film have a corundum crystal structure, it is possible to achieve a semiconductor layer and an insulating film of good quality on the base substrate.