SiC Trench Gate Insulating Film Segmentation for Breakdown Voltage
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices with trench gate structures have low dielectric breakdown resistance due to residual carbon atoms in the gate oxide film, limiting their breakdown voltage.
Innovation Solution
A silicon carbide semiconductor device with a trench structure featuring a gate insulating film comprising a trench insulating film and a bottom insulating film, where the bottom insulating film has a lower carbon atom concentration than the trench insulating film, ensuring high dielectric breakdown resistance and large breakdown voltage without increasing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate insulating film is formed entirely by thermal oxidation of the silicon carbide substrate, then low threshold voltage can be attained, but the breakdown voltage of the silicon carbide semiconductor device cannot be further increased
Solution Approach 1:
The gate insulating film is segmented into two functional layers: the first layer (trench insulating film) via thermal oxidation ensures low threshold voltage, while the second layer (bottom insulating film) via CVD ensures high breakdown voltage. This segmentation resolves the contradiction by assigning different optimization goals to different layers.
Solution Approach 2:
Different regions of the gate insulating film are given different material compositions and properties. The trench insulating film region is optimized for thinness and flatness to achieve low threshold voltage, while the bottom insulating film region is optimized for high dielectric breakdown resistance to achieve high breakdown voltage, allowing local optimization of different functional 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 device achieves a low threshold voltage and a large breakdown voltage by securing electric insulation between the gate electrode and the trench bottom with a bottom insulating film, while maintaining a thin and smooth trench insulating film, thus enhancing the dielectric breakdown resistance and operational performance.
Implementation Method 1
by performing a thermal oxidation process once, a thermal oxidation film can be formed such that the thickness of the thermal oxidation film on the side surface of the trench is greatly different from the thickness of the thermal oxidation film on the bottom surface of the trench
Data Source
AI summary
A gate insulating film is provided on a trench. The gate insulating film has a trench insulating film and a bottom insulating film. The trench insulating film covers each of a side wall and a bottom portion. The bottom insulating film is provided on the bottom portion with a trench insulating film being interposed therebetween. The bottom insulating film has a carbon atom concentration lower than that of the trench insulating film. The gate electrode is in contact with a portion of the trench insulating film on the side wall. Accordingly, a low threshold voltage and a large breakdown voltage can be attained.