MOSFET Edge Termination Structure for Higher Breakdown Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional edge termination structures in power metal oxide semiconductor field-effect transistors (MOSFETs) with shallow body junctions fail to maximize breakdown voltage, leading to punch-through breakdown and increased manufacturing complexity.
Innovation Solution
The introduction of shallow 'sandwich' double junction structures in the termination area, combined with various field plate designs and a transition zone between the active and termination areas, including polysilicon fingers and compensating dopant, to enhance breakdown voltage without increasing process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional edge termination structures are used in power MOSFETs with shallow body junctions, then the device structure is simple, but the breakdown voltage is not maximized and punch-through breakdown occurs
Solution Approach 1:
The patent implements an N-P-N sandwich structure where a first P-type region is formed within an N-type region that is itself formed within a second P-type region. This nested configuration creates multiple junctions (first PN junction and second PN junction) that work together to enhance breakdown voltage without requiring completely separate termination structures, thus improving reliability while controlling complexity.
Solution Approach 2:
The patent extends the termination structure into the vertical dimension by forming the N-P-N sandwich structure with regions extending to different depths. The first P-type region, N-type region, and second P-type region are positioned at different vertical levels, creating a three-dimensional termination architecture that increases breakdown voltage without significantly increasing lateral footprint or process complexity.
2Productivity
If shallow body junctions are used in power MOSFETs, then channel length is reduced and conduction losses decrease, but punch-through breakdown and increased manufacturing complexity occur
Solution Approach 1:
The patent forms the N-type region and first P-type region in the termination area before final device completion. This preliminary structuring of the N-P-N sandwich configuration creates pre-positioned depletion regions that will actively prevent punch-through breakdown when the device is operated, addressing the reliability issue before it manifests during device operation.
Solution Approach 2:
The patent applies the N-P-N sandwich structure specifically to the termination area rather than throughout the entire device. The first P-type region, N-type region, and second P-type region are localized to the edge termination zone where punch-through breakdown is most likely to occur, providing targeted protection while maintaining short channel characteristics in the active device region.
3Reliability
If complex termination structures are implemented to increase breakdown voltage, then reliability improves, but manufacturing complexity increases
Solution Approach 1:
The N-type region in the sandwich structure serves multiple functions: it forms the second PN junction with the second P-type region for breakdown voltage enhancement, and it also acts as the body region for the vertical power device. This multi-functionality reduces the need for separate dedicated termination structures, simplifying manufacturing while maintaining high breakdown voltage.
Solution Approach 2:
The patent combines the termination structure with the main device body by using the N-type region as both the termination N-type region and the device body. The first P-type region and second P-type region are integrated with the termination structure rather than being separate components, merging multiple functions into a unified structure that is easier to manufacture.
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 improves punch-through voltage, maintains low manufacturing complexity, and allows for short channels with increased breakdown voltage, effectively preventing voltage breakdown and punch-through in MOSFET devices.
Implementation Method 1
it is noted that the trench corner may enhance an electric field which may lead to a reduction in a breakdown voltage of the edge termination area
Implementation Method 2
the trench corner may enhance an electric field which may lead to a reduction in a breakdown voltage of the edge termination area
Implementation Method 3
RFP structure to limit the depletion region spreading into the body region
Data Source
AI summary
A MOSFET switch which has a low surface electric field at an edge termination area, and also has increased breakdown voltage. The MOSFET switch has a new edge termination structure employing an N-P-N sandwich structure. The MOSFET switch also has a polysilicon field plate configuration operative to enhance any spreading of any depletion layer located at an edge of a main PN junction of the N-P-N sandwich structure.