SiC MOSFET Guard Ring Curvature Optimization
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Solution Overview
Problem
Silicon carbide MOSFETs face breakdown due to electric field concentration at the corner portion of the guard ring, and increasing the radius of curvature to alleviate this results in a decrease in on-state current.
Innovation Solution
Configuring the silicon carbide semiconductor device with a guard ring region where the radius of curvature of the inner circumference portion divided by the thickness of the drift region is between 5 and 10, and incorporating a JTE region and field stop region to improve breakdown voltage while maintaining on-state current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radius of curvature of the guard ring is increased to relax electric field concentration, then breakdown voltage is improved, but the area of the element region decreases resulting in decreased on-state current
Solution Approach 1:
The patent applies parameter changes by optimizing the radius of curvature within a specific range (5-10 times the drift layer thickness) rather than simply increasing it indefinitely. This quantitative parameter optimization resolves the contradiction by finding the optimal value that provides sufficient electric field relaxation while preserving adequate element region area for high on-state current.
Solution Approach 2:
The patent applies local quality by differentiating the curvature requirements at different locations: the guard ring corner portions have large radius of curvature (5-10 times drift layer thickness) to relax electric field concentration, while the linear portions maintain smaller dimensions to preserve element region area. This spatial differentiation of geometric parameters resolves the contradiction between breakdown voltage and on-state current.
2Productivity
If the radius of curvature of the guard ring is kept small according to silicon device ratios, then on-state current is maintained, but electric field concentration causes device breakdown
Solution Approach 1:
The patent applies parameter changes by establishing a new design criterion for silicon carbide devices: the radius of curvature should be 5-10 times the drift layer thickness, which is larger than traditional silicon device ratios. This parameter change accounts for the different material properties of silicon carbide and simultaneously achieves both high on-state current and high breakdown voltage.
Solution Approach 2:
The patent applies composite materials by considering the unique properties of silicon carbide as a different material system compared to silicon. The invention recognizes that silicon carbide's wider band gap and different crystal structure require different geometric parameters, effectively treating it as a composite material system with distinct design rules that enable both high current and high voltage performance.
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 configuration enhances breakdown voltage while preventing a decrease in on-state current, effectively managing electric field concentration and improving device performance.
Implementation Method 1
a value obtained by dividing a radius of curvature of an inner circumference portion of the curvature region by a thickness of the drift region is set to be not less than 5 and not more than 10
Data Source
AI summary
A silicon carbide semiconductor device includes an element region and a guard ring region. A semiconductor element is provided in the element region. The guard ring region surrounds the element region in a plan view and has a first conductivity type. The semiconductor element includes a drift region having a second conductivity type different from the first conductivity type. The guard ring region includes a linear region and a curvature region continuously connected to the linear region. A value obtained by dividing a radius of curvature of an inner circumference portion of the curvature region by a thickness of the drift region is not less than 5 and not more than 10. Accordingly, there can be provided a silicon carbide semiconductor device capable of improving a breakdown voltage while suppressing decrease of on-state current.