Trench MOSFET Floating Gate Depth and Channel Stop Isolation
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Solution Overview
Problem
Trench MOSFETs with trenched floating gates in the termination area face issues of high leakage current and low breakdown voltage due to poor isolation between the drain and source regions, caused by shallow trenched floating gates and floating deep P body regions not being adequately connected.
Innovation Solution
The design features trenched floating gates in the termination area with a depth equal to or deeper than the body junction of surrounding body regions, without source regions, and includes trenched channel stop gates electrically connected to the epitaxial layer and drain region to maintain high breakdown voltage and prevent leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If trenched floating gates are made shallower in the termination area, then manufacturing is easier, but breakdown voltage is significantly degraded and leakage current increases
Solution Approach 1:
The patent changes the depth parameter of the trenched floating gates in the termination area, making them shallower than the floating deep P body regions. This parameter modification allows easier manufacturing while the floating deep P body regions extend deeper to maintain the required breakdown voltage and prevent leakage current.
2Device complexity
If source regions are disposed between adjacent trenched floating gates in termination, then device structure is completed, but heavily leakage current occurs between drain and source regions
Solution Approach 1:
The patent extracts or removes the source regions from the termination area, specifically preventing their disposition between adjacent trenched floating gates. This elimination of source regions from the termination area prevents the formation of leakage current paths between drain and source regions while the floating deep P body regions provide the necessary electrical isolation.
3Ease of manufacture
If trenched floating gates are not deep enough to reach body junction, then fabrication is simpler, but poor isolation occurs between drain and source regions
Solution Approach 1:
The patent introduces floating deep P body regions as an intermediary element that extends deeper than the trenched floating gates. These floating deep P body regions act as a mediator to provide the necessary electrical isolation between drain and source regions in the termination area, compensating for the shallower depth of the trenched floating gates and simplifying fabrication.
Data Source
AI summary
A trench MOSFET comprising multiple trenched floating gates in termination area is disclosed. The multiple trenched floating gates have trench depth equal to or deeper than body junction of body regions in active area. The trench MOSFET further comprises at least one trenched channel stop gate around outside of the trenched floating gates and connected to at least one sawing trenched gate extended into scribe line for prevention of leakage path formation between drain and source regions.