Split-Gate Trench MOSFET Structure for Lower Gate Oxide Stress
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Solution Overview
Problem
Gate oxide layers in power MOSFETs are prone to breakdown due to high electric fields, leading to device failure, which is exacerbated in gate trench designs, particularly in silicon carbide-based devices, where electric fields are higher and more concentrated at the lower corners of the gate oxide layers.
Innovation Solution
The gate electrode is divided into first and second regions, with a portion of the gate electrode removed from a third region between them, and a dielectric layer is used to separate these portions, reducing electric field intensity and capacitance, while trench shielding regions and support shields are employed to further mitigate electric field crowding effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a gate trench design is used to reduce device area, then the device footprint is reduced, but electric field concentration at the lower corners of the gate oxide layer increases causing breakdown
Solution Approach 1:
The gate electrode is divided into multiple segments along the gate trench, with insulating material placed between segments. This segmentation prevents continuous electric field lines from forming at the lower corners of the gate oxide layer, thereby reducing electric field concentration and preventing breakdown while maintaining the compact gate trench structure
Solution Approach 2:
An insulating material is introduced as an intermediary element between different portions of the gate electrode within the gate trench. This intermediary blocks the formation of high electric fields at critical locations (lower corners of the gate oxide layer) without requiring changes to the overall device footprint
2Loss of energy
If the gate electrode is made larger to reduce gate resistance, then conduction losses are reduced, but the electric field intensity at the gate oxide interface increases
Solution Approach 1:
The gate electrode is segmented into multiple portions with insulating material between them, allowing each segment to be optimized for local electric field management while collectively providing low gate resistance through parallel conduction paths
Solution Approach 2:
Different regions of the gate electrode are treated differently by introducing insulating material at specific locations (between gate electrode portions) while maintaining continuous gate control. This allows local reduction of electric field intensity at critical interfaces while preserving overall gate functionality and low resistance
3Ease of operation
If a continuous gate electrode is used to ensure uniform gate control, then gate control is simplified, but electric field crowding effects are exacerbated
Solution Approach 1:
The gate electrode is divided into multiple segments that are electrically connected, providing uniform gate control across the device while the insulating material between segments prevents electric field crowding at critical locations
Solution Approach 2:
Insulating material acts as an intermediary between gate electrode segments, preventing direct electric field interaction at locations where crowding would occur, while the segments remain electrically connected to maintain uniform gate control
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 design enhances the reliability of gate trench power MOSFETs by extending the gate oxide lifetime and reducing power loss, making them suitable for high-frequency applications with lower conduction losses and improved switching speeds.
Implementation Method 1
reducing electric field intensity and capacitance
Implementation Method 2
reducing electric field intensity and capacitance
Implementation Method 3
the gate electrode of a MOSFET is insulated from the channel region by the gate oxide layer
Data Source
AI summary
Gate trench semiconductor devices having reduced capacitance between a semiconductor layer structure and a gate electrode thereof. For example, a semiconductor device may include a semiconductor layer structure that comprises a drift region having a first conductivity type, a well layer having a second conductivity type, and a source region having the first conductivity type; a first gate trench extending into an upper portion of the semiconductor layer structure; a first dielectric layer within the first gate trench and conforming to an interior perimeter of the first gate trench; and a first gate electrode within the first gate trench and on the first dielectric layer. The gate electrode may have first and second portions that are spaced apart from each other by a second dielectric layer.