Deep Trench Shield Connections for Gate Oxide Protection in MOSFETs
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Solution Overview
Problem
Gate oxide layers in power semiconductor devices, particularly gate trench MOSFETs, are susceptible to breakdown due to high electric fields, leading to device failure, and existing solutions like trench shields and support shields increase device pitch and fabrication complexity.
Innovation Solution
Incorporation of deep trench shield connection patterns that extend deeper into the semiconductor layer structure than traditional trench shields, redirecting displacement and avalanche currents away from the gate oxide layers, thereby reducing electric field stress and eliminating the need for support shields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trench shields and support shields are used to protect gate oxide layers from high electric fields, then gate oxide breakdown is prevented, but device pitch increases and fabrication complexity increases
Solution Approach 1:
The invention extracts the support shield structure from the device architecture, eliminating the need for separate support shields while maintaining gate oxide protection through optimized trench shield connection patterns that extend deeper into the drift region
Solution Approach 2:
The invention merges the functions of trench shields and support shields into a single integrated trench shield structure with extended connection patterns, where the trench shield connection pattern performs both the shielding function and the current redistribution function previously requiring separate support shields
2Reliability
If trench shields and support shields are used to protect gate oxide layers, then gate oxide breakdown is prevented, but device pitch increases
Solution Approach 1:
The invention removes the support shield structure that was occupying additional lateral space, allowing devices to be placed closer together while maintaining adequate electric field management through the optimized trench shield design
3Reliability
If deep trench shield connection patterns are used to redirect currents, then electric field stress on gate oxide is reduced, but fabrication complexity increases
Solution Approach 1:
The trench shield connection pattern serves multiple functions simultaneously: it provides electric field shielding, redistributes displacement and avalanche currents, and eliminates the need for separate support shield fabrication steps, thereby maintaining ease of manufacture while improving reliability
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
Enhances device reliability by reducing electric field stress on gate oxide layers, allowing for higher on-state currents and voltage blocking capabilities while maintaining a reduced cell pitch and simplifying fabrication.
Implementation Method 1
redirecting displacement and avalanche currents away from the gate oxide layers
Data Source
AI summary
A semiconductor device comprises a semiconductor layer structure that has a gate trench therein and a source metallization layer on the semiconductor layer structure. The semiconductor layer structure comprises a drift region having a first conductivity type, a trench shield that has a second conductivity type, the trench shield positioned underneath the gate trench, and a trench shield connection pattern that has the second conductivity type, the trench shield connection pattern electrically connecting the trench shield to the source metallization layer, where the trench shield connection pattern extends deeper into the semiconductor layer structure than the trench shield.