SiC Electric Field Relaxation Structure for Fewer Epitaxial Layers
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Solution Overview
Problem
The conventional manufacturing of silicon carbide semiconductor devices requires forming multiple epitaxial layers, which increases costs and complexity.
Innovation Solution
A silicon carbide semiconductor device design that reduces the number of epitaxial layers by incorporating a specific electric field relaxation region with graded impurity concentrations, allowing for the formation of the source, body, and drift regions without multiple epitaxial layers, while enhancing breakdown voltage and suppressing short-circuit current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple epitaxial layers are formed to create source, body, and drift regions, then the device structure can be achieved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent merges the source region, body region, and drift region into a single epitaxial layer structure. The source and body regions are formed as adjacent doped regions within the same epitaxial layer, while the drift region extends beneath them, eliminating the need for multiple separate epitaxial layers and reducing manufacturing complexity
Solution Approach 2:
The patent applies local quality by creating regions with different impurity concentrations and conductivity types within a single epitaxial layer. The source and body regions have high impurity concentrations for good conductivity, while the drift region has lower impurity concentration for high breakdown voltage, all within one continuous layer structure
2Strength
If the electric field relaxation region has a steep impurity concentration gradient, then the breakdown voltage can be improved, but the short-circuit current increases
Solution Approach 1:
The patent changes the impurity concentration parameter in the electric field relaxation region to have a specific gradient profile. The impurity concentration decreases from the interface with the drift region toward the second main surface, with the concentration at the interface being 1×10^16 to 1×10^18 atoms/cm³ and decreasing to lower values, optimizing both breakdown voltage and short-circuit current characteristics
Solution Approach 2:
The patent creates a dynamic impurity concentration profile in the electric field relaxation region where the concentration varies continuously with depth. This gradual transition zone with specific concentration gradients allows the electric field to be distributed optimally, preventing both premature breakdown and excessive short-circuit current flow
Data Source
AI summary
A silicon carbide semiconductor device includes a silicon carbide substrate that has first and second main surfaces and that includes a drift region being of a first-conductivity-type, a body region provided on the drift region and being of a second-conductivity-type, a source region provided on the body region and being of the first-conductivity-type, and a first electric field relaxation region being of the second-conductivity-type and including a first plane in which an impurity-concentration of the second-conductivity-type is a maximum and a second plane in which the impurity-concentration of the second-conductivity-type of 1/10 of the maximum, the second plane being closer to the second main surface than the first plane is. A distance between the first and second planes is 1.0 μm or greater, and a distance from the first main surface to an interface between the first electric field relaxation region and the drift region is 2.0 μm or greater.