Shielded Gate Trench MOSFET Termination Layout for Avalanche Control
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Solution Overview
Problem
Existing shielded gate trench (SGT) MOSFETs face challenges such as early avalanche at the intersection of single termination trenches and gate trenches, degraded device ruggedness due to lack of body contacts under the gate metal pad, and instability in breakdown voltage with high shielded gate resistance.
Innovation Solution
The proposed SGT MOSFET features a wave shape trench design in the first termination trench to reduce electric fields, optimized shielded gate trench contacts spaced apart from gate metal runners, and a combination of multiple stepped epitaxial (MSE) and multiple stepped oxide (MSO) structures to reduce specific on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single termination trench is used to surround multiple gate trenches, then device structure is simplified, but early avalanche occurs at the intersection of termination trench and gate trenches
Solution Approach 1:
The single termination trench is divided into multiple separate termination trenches, each positioned to terminate gate trenches independently. This segmentation prevents the concentration of electric field at a single intersection point, thereby eliminating early avalanche while maintaining structural simplicity through regular spacing and configuration.
Solution Approach 2:
The termination trenches are positioned at specific locations where electric field concentration would occur, providing localized field termination. This local quality approach targets the critical regions near gate trench intersections without requiring complete structural redesign, effectively preventing early avalanche at these specific points.
2Loss of time
If shielded gate resistance is increased to reduce reverse recovery time, then reverse recovery charge decreases, but breakdown voltage becomes unstable
Solution Approach 1:
The shielded gate resistance is optimized to a specific parameter range rather than simply increased. By carefully selecting the resistance value and positioning, the design achieves reduced reverse recovery charge while maintaining breakdown voltage stability, resolving the contradiction through precise parameter control.
Solution Approach 2:
The shielded gate structure acts as an intermediary element between the gate and source, providing a controlled resistance path. This intermediary structure enables the balancing of reverse recovery performance and breakdown voltage stability by mediating the electrical characteristics in the shielded gate region.
3Reliability
If wave shape portions are added to termination trenches to reduce electric field, then device ruggedness is enhanced, but manufacturing complexity increases
Solution Approach 1:
Wave shape portions with curved profiles are introduced to the termination trenches to reduce electric field concentration. The curved geometry redistributes the electric field more uniformly, enhancing device ruggedness. The curvature is designed to be compatible with standard fabrication processes, balancing performance improvement with manufacturability.
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 configuration enhances device ruggedness, reduces drain-source leakage current, and stabilizes breakdown voltage while maintaining low specific on-resistance, making it suitable for high-frequency applications.
Implementation Method 1
Inner edges of a first termination trench of the termination trenches adjacent to trench ends of the gate trenches have a plurality of wave shape portions in regions between two adjacent trench ends of the gate trenches
Implementation Method 2
shielded gate trench contacts spaced apart from gate metal runners with an optimized distance for high frequency applications
Implementation Method 3
combination of multiple stepped epitaxial (MSE) and multiple stepped oxide (MSO) structures to reduce specific on-resistance
Data Source
AI summary
Shielded gate trench MOSFETs with gate trenches separated from termination trenches are disclosed, wherein the termination trenches surrounds outer periphery of gate trenches and do not surround said gate metal pad area; Inner edges of a first termination trench of the termination trenches adjacent to trench ends of the gate trenches have a plurality of wave shape portions in regions between two adjacent trench ends of the gate trenches while outer edges have a straight shape to reduce drain-source leakage current. Each of gate trenches on which has at least one shielded gate trench contact connected to a shielded gate electrode, and the shielded gate trench contact is spaced apart from any of multiple gate metal runners with a distance larger than 100 um.