SiC MOSFET Trench Gate Termination for Breakdown Voltage
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Solution Overview
Problem
Silicon carbide (SiC) MOSFETs with trench gate structures face challenges in achieving high breakdown voltage due to electric field concentration in electric field relaxation regions, which reduces their reliability and efficiency.
Innovation Solution
Incorporating a termination region with specific trench structures and p-type silicon carbide regions with controlled impurity concentrations and depths, along with a gate trench structure, to alleviate electric field concentration and enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electric field relaxation regions are provided deeper than the trench to improve gate insulating layer reliability, then the reliability of gate insulating layer is improved, but electric fields are concentrated in the electric field relaxation regions at the ends of the element region, reducing breakdown voltage
Solution Approach 1:
The patent applies local quality by creating different impurity concentration zones within the electric field relaxation region. Specifically, it introduces a first impurity region with a first impurity concentration and a second impurity region with a second impurity concentration that is lower than the first. This gradient structure allows the electric field to be distributed more evenly across the termination region, preventing concentration at the element region ends while still protecting the gate insulating layer. The localized modification of impurity concentrations optimizes both reliability and breakdown voltage without requiring uniform structural changes throughout the device.
2Loss of energy
If trench gate structure is applied to increase channel area and reduce on-resistance, then on-resistance is reduced, but electric field concentration occurs in termination regions, reducing breakdown voltage
Solution Approach 1:
The patent employs parameter changes by systematically varying the impurity concentration parameters within the termination region. It establishes a first impurity region with higher concentration and a second impurity region with lower concentration, creating a controlled gradient. This parameter optimization allows the device to maintain low on-resistance through the trench gate structure while simultaneously improving breakdown voltage by preventing electric field concentration. The method transforms the termination region from a passive structure into an actively optimized zone with tailored electrical properties.
3Strength
If termination structure is provided to improve breakdown voltage around element region, then breakdown voltage is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the termination region into distinct impurity concentration zones - a first impurity region and a second impurity region with different concentration levels. This segmented approach to doping allows precise control over electric field distribution without requiring complex geometric structures. The segmentation occurs at the material composition level rather than through additional physical structures, thereby improving breakdown voltage while minimizing increases in device complexity. The method achieves enhanced performance through controlled material properties rather than structural elaboration.
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 proposed solution effectively improves the breakdown voltage and reliability of SiC MOSFETs by redistributing electric fields, reducing on-resistance, and stabilizing the breakdown voltage.
Implementation Method 1
the electric fields may be concentrated in the electric field relaxation regions at the ends of the element region, and the breakdown voltage of the MOSFET may be reduced. Therefore, even when the electric field relaxation regions are provided, it is desired to provide a termination structure that improves the breakdown voltage of the MOSFET around the element region
Data Source
AI summary
A semiconductor device of an embodiment includes an element region and a termination region surrounding the element region. The element region includes a gate trench, a first silicon carbide region of n-type, a second silicon carbide region of p-type on the first silicon carbide region, a third silicon carbide region of n-type on the second silicon carbide region, and a fourth silicon carbide region of p-type sandwiches the first silicon carbide region and the second silicon carbide region with the gate trench, the fourth silicon carbide region being deeper than the gate trench. The termination region includes a first trench surrounding the element region, and a fifth silicon carbide region of p-type between the first trench and the first silicon carbide region, the fifth silicon carbide region same or shallower than the fourth silicon carbide region. The semiconductor device includes a gate electrode, a first electrode, and a second electrode.