SiC Substrate Nitride-Oxide Stack for Low Interface State Density
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Solution Overview
Problem
High interface state density between silicon carbide semiconductor substrates and gate insulating films leads to decreased channel mobility, necessitating a semiconductor substrate with reduced interface state density and improved mobility.
Innovation Solution
A semiconductor substrate is designed with a silicon carbide substrate, a nitrogen-enriched first nitride film, a second nitride film, and a silicon oxide film, where the first nitride film is more nitrogen-rich than the second, and the silicon oxide film is thicker than the combined nitride films, suppressing oxygen diffusion and maintaining nitrogen bonding at the interface to reduce interface state density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a gate insulating film is provided directly on the silicon carbide substrate, then the device structure is simple, but the interface state density increases and channel mobility decreases
Solution Approach 1:
The gate insulating film is segmented into multiple layers: a first nitride film layer, a second nitride film layer, and a silicon oxide film layer. This segmentation allows each layer to perform specific functions - the nitride layers reduce interface state density while the oxide layer provides insulation, thereby improving channel mobility without excessive structural complexity
Solution Approach 2:
The gate insulating film uses a composite structure combining nitride materials and silicon oxide materials. The nitride layers (SiNx) are specifically designed to reduce interface state density at the silicon carbide interface, while the silicon oxide layer provides the necessary insulating properties, achieving both low interface state density and high channel mobility
2Reliability
If the silicon oxide film is made thicker to suppress oxygen diffusion, then interface state density is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The thickness of the silicon oxide film is optimized to a specific range (5 nm to 50 nm) to achieve the right balance between suppressing oxygen diffusion and maintaining manufacturability. This parameter optimization ensures sufficient oxygen barrier functionality while avoiding excessive thickness that would complicate the manufacturing process
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 approach results in a semiconductor substrate with high channel mobility and low interface state density, maintaining the bonding between the silicon carbide substrate and the upper layers, thereby enhancing the substrate's performance.
Implementation Method 1
a first nitride film in contact with an upper surface of the silicon carbide substrate... The first nitride film is more nitrogen-enriched than the second nitride film
Implementation Method 2
a silicon oxide film in contact with an upper surface of the second nitride film... suppressing oxygen diffusion
Data Source
AI summary
A semiconductor substrate includes a silicon carbide substrate, a first nitride film in contact with the upper surface of the silicon carbide substrate, a second nitride film in contact with an upper surface of the first nitride film, and a silicon oxide film in contact with the upper surface of the second nitride film. The first nitride layer is more nitrogen-rich than the second nitride layer.