MOSFET Edge Termination with N-P-N Sandwich Structure
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 combined with trench field plates and a transition zone between the active area and edge termination region, which includes polysilicon fingers and compensating dopant, enhances 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 manufacturing complexity is reduced, but breakdown voltage is not maximized and punch-through breakdown occurs
Solution Approach 1:
The edge termination structure is segmented into multiple functional zones: a first termination zone with a first doping concentration and a second termination zone with a second doping concentration. This segmentation allows each zone to perform its specific function optimally, with the first zone preventing punch-through and the second zone controlling breakdown voltage, thereby resolving the contradiction between reliability and structural simplicity.
Solution Approach 2:
Different regions of the edge termination are assigned different doping concentrations tailored to their specific requirements. The first termination zone has a higher doping concentration to prevent punch-through breakdown, while the second termination zone has a lower doping concentration to control avalanche breakdown voltage. This local differentiation optimizes performance without requiring complex overall structure.
2Productivity
If shallow body junctions are used to reduce channel length, then conduction and switching power losses are reduced, but breakdown voltage decreases and punch-through breakdown occurs
Solution Approach 1:
The edge termination structure is designed with pre-doped regions that perform preliminary electrical isolation before the main channel operation. The first termination zone with higher doping concentration is formed in advance to create an electrical barrier that prevents punch-through of the shallow body junction, allowing the short channel to function without suffering from breakdown issues.
Solution Approach 2:
The first termination zone acts as an intermediary structure between the shallow body junction and the edge termination region. It mediates the electrical field distribution, preventing direct punch-through of the shallow junction while allowing the second termination zone to control the overall breakdown voltage, thus enabling short-channel operation with maintained reliability.
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-channel MOSFETs with increased breakdown voltage, effectively preventing voltage breakdown and punch-through in the edge termination area.
Implementation Method 1
introducing, into the semiconductor substrate, a compensating dopant to a concentration that improves a breakdown voltage of the power semiconductor device by neutralizing an effect of positive charge in the semiconductor substrate
Implementation Method 2
The edge termination structure employs an N-P-N sandwich structure... effectively preventing voltage breakdown and punch-through in the edge termination area
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.