SiC Trench MOSFET Shield Layout for Gate Oxide Field Relief
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Solution Overview
Problem
Power MOSFETs with gate trenches are susceptible to gate oxide breakdown due to high electric fields, leading to reduced device lifetime and potential short-circuit failure.
Innovation Solution
The semiconductor device incorporates a silicon carbide based semiconductor layer structure with a drift region, implanted regions, and gate trench sections. A support shield with a different maximum depth than the trench shielding regions is used to reduce electric field levels and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate trenches are used in power MOSFETs to improve current conduction and switching performance, then device performance is improved, but the device becomes susceptible to gate oxide breakdown due to high electric fields
Solution Approach 1:
A support shield region is introduced as an intermediary structure between the gate trench and the drift region. This support shield acts as a mediator that redistributes the electric field stress, preventing direct concentration of high electric fields at the gate oxide interface while maintaining the beneficial current conduction paths of the gate trench structure
Solution Approach 2:
The support shield region is strategically positioned at specific locations where electric field concentration occurs, creating local modifications to the electric field distribution. This localized intervention addresses the high electric field stress problem at critical points without altering the overall gate trench structure or compromising device performance
2Reliability
If trench shielding regions are added to protect against electric field stress, then gate oxide protection is improved, but device complexity increases
Solution Approach 1:
The support shield region is merged with the existing drift region and other doped regions in the device structure. By combining the protective function with existing structural elements, the patent achieves gate oxide protection without adding completely separate, independent structures that would increase device complexity
3Reliability
If support shields with different depths are used to optimize electric field distribution, then electric field stress reduction is improved, but manufacturing precision requirements increase
Solution Approach 1:
The shielding structure is segmented into multiple regions (trench shielding regions and support shield regions) with different depths and positions. This segmentation allows each region to be optimized for its specific function while using standard implantation techniques, making the different depth requirements achievable with conventional manufacturing processes
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 design effectively reduces the risk of gate oxide breakdown, improving the reliability and longevity of the power MOSFET by distributing electric field stress and providing a primary current path during avalanche events.
Implementation Method 1
Power MOSFETs with gate trenches are susceptible to gate oxide breakdown due to high electric fields
Implementation Method 2
A first conductivity type drift region and a second conductivity type implanted region on the drift region
Data Source
AI summary
A semiconductor device comprises a silicon carbide based semiconductor layer structure that comprises a drift region having a first conductivity type and an implanted region having a second conductivity type on the drift region. First and second gate trench sections extend into the semiconductor layer structure. A first maximum depth into the semiconductor layer structure of a first portion of the implanted region that is between the first gate trench section and the second gate trench section is different than a second maximum depth into the semiconductor layer structure of a second portion of the implanted region that extends downwardly underneath the first gate trench section.