Trench Gate FET Edge Termination via Shallower Body Regions
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Solution Overview
Problem
Conventional trench gate FET designs require complex and costly manufacturing processes due to the need for additional process steps in forming edge termination structures, which can compromise the RESURF effect and increase the risk of device failure.
Innovation Solution
The design incorporates self-aligned source contact regions and edge termination structures with shallower body regions in termination cells, allowing for effective edge termination without additional process steps, thereby maintaining the RESURF condition and enhancing breakdown voltage while reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field rings or field plates are used for edge termination, then effective edge termination is achieved, but the number of process steps increases significantly
Solution Approach 1:
The patent combines the edge termination function with the existing body region structure by extending the body region into the termination region. This merging eliminates the need for separate field rings or field plates, achieving effective edge termination while reducing the number of process steps and manufacturing complexity.
Solution Approach 2:
The body region serves multiple functions: it provides the standard function in active cells and simultaneously provides edge termination in termination cells. This multi-functionality eliminates the need for dedicated edge termination structures, reducing device complexity while maintaining reliability.
2Reliability
If field rings or field plates are used for edge termination, then breakdown voltage is maintained, but manufacturing cost increases
Solution Approach 1:
The patent merges the edge termination function with the existing body region, eliminating the need for additional field rings or field plates. This reduces manufacturing cost by removing extra process steps while maintaining the breakdown voltage through the extended body region structure.
3Reliability
If conventional edge termination structures are used, then edge termination is provided, but trench spacing must be larger
Solution Approach 1:
The patent transitions from two-dimensional field plates or rings to a three-dimensional structure by extending the body region vertically into the termination region. This dimensional change allows for more compact trench spacing while maintaining effective edge termination through the depth-controlled body region extension.
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 enables improved RESURF effect and breakdown voltage performance with reduced manufacturing complexity and cost, allowing for closer trench spacing and lower on-resistance, thus preventing edge cell damage from high current density.
Implementation Method 1
Such transistors often leverage the reduced surface field (RESURF) effect to achieve a relatively low on resistance (RDSon) while maintaining a relatively high breakdown voltage (BVdss). The trench gate design also may employ a termination region at a periphery or one or more edges of the active region so as to provide effective edge termination by spreading out the electric field at the edges of the active region.
Data Source
AI summary
A semiconductor device includes a semiconductor layer disposed at a substrate and a plurality of active cells disposed at the semiconductor layer. Each active cell includes a trench extending into the semiconductor layer and a body region disposed in the semiconductor layer adjacent to a sidewall of the trench and at a first depth below the surface of the semiconductor layer. The semiconductor device further includes a termination cell disposed at the semiconductor layer adjacent to an edge of the plurality of active cells. The termination cell includes a trench extending into the semiconductor layer, and further includes a body region disposed in the semiconductor layer adjacent to a sidewall of the trench of the termination cell and at a second depth less than the first depth. The body regions of the active cells and of the termination cell have a conductivity type different than that of the semiconductor layer.