Super-junction MOSFET Edge Termination Segmentation
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Solution Overview
Problem
Super-junction MOSFETs require effective edge termination to achieve increased breakdown voltage in a reduced distance, particularly for plate-type structures, while maintaining compatibility with existing integrated circuit design and manufacturing processes.
Innovation Solution
The implementation of a termination region with separated floating termination segments surrounding the core region, where each segment has a length less than the core plates, configured to force breakdown into the core region and not in the termination region, ensuring a higher breakdown voltage than the core region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional edge termination structures are used for super-junction MOSFETs, then the device can achieve adequate breakdown voltage, but the edge termination width becomes excessively large, reducing device integration density
Solution Approach 1:
The termination region is divided into multiple separated floating termination segments rather than using a continuous termination structure. Each segment has a length dimension less than the core plates and is separated from adjacent segments by regions of the first conductivity. This segmentation allows the termination to achieve adequate breakdown voltage while significantly reducing the total width of the termination region compared to conventional continuous termination structures.
Solution Approach 2:
The patent applies different structural characteristics to different regions: the core region contains alternating plates of first and second conductivity types with specific charge relationships, while the termination region contains separated floating segments of the second conductivity type. This local differentiation allows each region to be optimized for its specific function - the core for charge balance and the termination for breakdown voltage control - thereby achieving high breakdown voltage in a compact width.
2Manufacturing precision
If plate type structures are used in the drift region, then manufacturing variation in charge is reduced, but directional asymmetry creates challenges for termination scheme development
Solution Approach 1:
The termination region is segmented into multiple separated floating termination segments rather than using a continuous structure. This segmentation approach simplifies the termination scheme by creating discrete, manageable units that can be independently configured to manage the directional asymmetry of plate type structures while maintaining charge balance requirements.
Solution Approach 2:
Instead of attempting to make the termination region perfectly symmetric to match the plate structures, the patent inverts the approach by using asymmetric separated floating segments that exploit the directional characteristics of plate structures. The segments are positioned and dimensioned to work with rather than against the inherent directional asymmetry, simplifying the overall termination design.
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 approach enhances the unclamped inductive-switching (UIS) capability of the device by maintaining charge balance and increasing breakdown voltage, reducing the edge termination width significantly compared to conventional methods, thereby improving the performance of super-junction MOSFETs.
Implementation Method 1
The termination region is configured to have a higher breakdown voltage than the core region. Each termination segment has a length dimension less than a length dimension of the core plates, and the segments are separated from one another by regions of the first conductivity.
Data Source
AI summary
Edge termination for MOSFETs. In accordance with an embodiment of the present invention, a metal oxide semiconductor field effect transistor (MOSFET) includes a core region including a plurality of parallel core plates coupled to a source terminal of the MOSFET. The MOSFET also includes a termination region surrounding the core region comprising a plurality of separated floating termination segments configured to force breakdown into the core region and not in the termination region. Each termination segment has a length dimension less than a length dimension of the core plates.