Gate Trench MOSFET Shielding Layout for Avalanche Robustness
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Solution Overview
Problem
Gate oxide layers in power MOSFETs are susceptible to breakdown due to high electric fields, leading to premature device failure, and existing solutions like trench shielding and support shields compromise device integration and fabrication complexity.
Innovation Solution
Incorporating gate trenches with non-uniform widths and trench shielding regions in the semiconductor layer structure, along with conductive taps, to reduce electric field stress and enhance avalanche robustness without increasing fabrication complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trench shielding regions are added to protect gate oxide, then gate oxide reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines the trench shielding region with the gate trench structure itself, making them a single integrated feature rather than separate components. The gate trench serves both as the gate electrode housing and as the shielding structure, eliminating the need for additional separate shielding regions and reducing overall device complexity while maintaining reliability benefits.
Solution Approach 2:
The gate trench structure is designed to perform multiple functions simultaneously: it houses the gate electrode, provides electrical isolation via gate oxide, and acts as a shielding region to protect against electric field stress. This multi-functionality eliminates the need for separate dedicated shielding structures, reducing device complexity while improving gate oxide reliability.
2Reliability
If support shields are added to prevent gate oxide breakdown, then gate oxide protection is improved, but fabrication complexity increases
Solution Approach 1:
The patent merges the support shield function into the gate trench structure by forming the shielding region within the same etching and filling process used for the gate trench. This integration means that a single fabrication sequence accomplishes both the gate electrode formation and the shielding structure creation, eliminating the need for separate support shield fabrication steps.
Solution Approach 2:
The shielding region is formed during the gate trench fabrication process itself, before subsequent device processing steps. By preparing the shielding structure in advance as part of the gate trench formation, the patent eliminates the need for later addition of separate support shields, simplifying the overall fabrication process while maintaining protection against gate oxide breakdown.
3Ease of manufacture
If gate trenches with uniform width are used, then fabrication is simplified, but avalanche robustness is reduced
Solution Approach 1:
The patent applies local quality by varying the gate trench width along its length, with narrower sections positioned at critical locations where electric field stress is highest during avalanche conditions. This non-uniform width distribution provides enhanced shielding precisely where needed, improving avalanche robustness without requiring uniform complexity throughout the entire structure.
Solution Approach 2:
The gate trench is designed with asymmetric width characteristics, featuring different widths at different positions along its length rather than a symmetric uniform width. This asymmetric design allows the trench to provide differential shielding at different locations, optimizing avalanche protection at critical field regions while maintaining overall fabrication feasibility through a single etch process with appropriate masking.
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
The solution reduces the likelihood of gate oxide failure during avalanche conditions, maintains channel density, and integrates easily with existing fabrication processes, while improving device performance.
Implementation Method 1
trench shielding regions in the semiconductor layer structure beneath a bottom of the gate trench... to reduce electric field stress and enhance avalanche robustness
Data Source
AI summary
A semiconductor device includes a semiconductor layer structure including a drift region, a gate trench in the semiconductor layer structure extending in a first direction parallel to an upper surface of the semiconductor layer structure, and a trench shielding region in the semiconductor layer structure beneath a bottom of the gate trench. The trench shielding region includes a first portion having a uniform width in a third direction, parallel to the upper surface of the semiconductor layer structure and perpendicular to the first direction, at a first depth in a second direction perpendicular to the upper surface of the semiconductor layer structure and a second portion having a non-uniform width in the third direction at the first depth in the second direction.