Semiconductor Edge Termination Trenches for Avalanche Ruggedness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Transistor devices for power applications face challenges in avalanche robustness and on-state resistance due to edge discontinuities that create high electric fields, leading to potential overheating and device failure, especially when voltage requirements vary across different device regions.
Innovation Solution
A semiconductor device with an edge termination region that includes a continuous dielectric-filled trench surrounding columnar termination trenches, combined with a buried doped region, which moves avalanche breakdown into the active cell area, reducing stress and improving avalanche performance without altering the active transistor cell design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If edge termination structures are designed to remove discontinuities at the edge, then electric field distribution is improved and breakdown voltage is increased, but device area is reduced and manufacturing complexity increases
Solution Approach 1:
The edge termination structure is segmented into multiple discrete columnar trenches arranged in a specific pattern, rather than using a continuous termination structure. This segmentation allows the electric field to be managed in localized regions while preserving more active device area, resolving the contradiction between reliability and area.
Solution Approach 2:
The columnar trenches are strategically positioned to create localized field management zones at the edge termination region. This local quality approach addresses the discontinuity problem only where needed at the edges, rather than modifying the entire device structure, thus maintaining maximum active area while improving breakdown voltage.
2Reliability
If columnar trenches with field plates are used in the active area, then charge compensation is improved and on-state resistance is reduced, but manufacturing complexity and stress management become more difficult
Solution Approach 1:
The invention merges the active columnar trenches in the cell field with the edge termination columnar trenches into a unified structure. Both use the same field plate configuration and trench geometry, simplifying the manufacturing process by using a single fabrication sequence for both regions while maintaining the charge compensation benefits in the active area.
Solution Approach 2:
The columnar trench structure serves dual functions: it provides charge compensation in the active cell field and simultaneously acts as the edge termination structure. This multi-functionality reduces manufacturing complexity by eliminating the need for separate termination structures while maintaining low on-state resistance.
3Reliability
If the active cell field is laterally surrounded by an edge termination structure, then breakdown due to edge effects is avoided, but the avalanche current density increases and overheating risk rises
Solution Approach 1:
The edge termination is segmented into discrete columnar trenches that allow avalanche current to spread laterally between the trenches, reducing current density. The segmented structure provides breakdown protection while creating pathways for current distribution, preventing localized overheating.
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 solution enhances avalanche ruggedness and reduces on-state resistance by distributing avalanche current evenly, increasing the active area and improving switching characteristics while minimizing unnecessary termination capacitance.
Implementation Method 1
The at least one continuous trench is filled with at least one dielectric material
Implementation Method 2
each including a field plate for charge compensation
Implementation Method 3
Avalanche breakdown is the phenomenon of current multiplication when a semiconductor device is subject to high electric fields
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
In an embodiment, a semiconductor device is provided that comprises a semiconductor body comprising an active area, wherein the active area comprises a plurality of active transistor cells, each active transistor cell comprising a columnar trench comprising a field plate and a mesa, and an edge termination region that laterally surrounds the active area. The edge termination region comprises a transition region that laterally surrounds the active region and an outer termination region that laterally surrounds the transition region. The edge termination region further comprises a plurality of inactive cells arranged in the transition region and in the outer termination region, each inactive cell comprising a columnar termination trench comprising a field plate and a termination mesa comprising a drift region of a first conductivity type. In the transition region, the termination mesa comprises a body region of the second conductivity type arranged on the drift region and in the outer termination region the drift region of the termination mesa extends to the first surface. The edge termination region further comprises at least one continuous trench that is positioned in the outer termination region and that laterally surrounds the columnar termination trenches and is filled with at least one dielectric material.