IGBT Cell Layout With Shield Region Against Trench Avalanches
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Solution Overview
Problem
Power semiconductor devices experience issues with high electric fields at the trench bottoms during switching operations, leading to potential dynamic avalanches that jeopardize correct functionality.
Innovation Solution
A power semiconductor device design featuring a shield region of a second conductivity type that extends further than the trench bottoms of control trenches, providing a greater lateral overlap with first type mesas while minimizing overlap with second type mesas, thereby shielding control trenches and reducing the likelihood of dynamic avalanches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trenches are extended deeper into the semiconductor body to improve control, then the control capability is enhanced, but high electric fields at the trench bottoms cause dynamic avalanches that jeopardize device functionality
Solution Approach 1:
A shield region of second conductivity type is introduced as an intermediary element between the control trenches and the drift region. This shield region extends deeper than the trench bottoms and creates a lateral overlap with first type mesas, effectively mediating the electric field distribution and preventing direct exposure of trench bottoms to harmful high electric fields that cause dynamic avalanches.
Solution Approach 2:
The shield region is selectively positioned to create different overlap conditions with different mesa types. It provides greater lateral overlap with first type mesas (controlling the inversion channel) while minimizing overlap with second type mesas, thereby locally tailoring the electric field shielding effect to specific functional requirements of different regions.
2Reliability
If the shield region is extended to provide greater lateral overlap with first type mesas, then dynamic avalanche is reduced, but the device structure becomes more complex
Solution Approach 1:
The shield region is designed with asymmetric spatial configuration, extending preferentially towards first type mesas to create greater lateral overlap, while intentionally minimizing overlap with second type mesas. This asymmetric design optimizes the shielding effect for critical regions (first type mesas controlling the inversion channel) without unnecessarily complicating the overall device structure.
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 occurrence of dynamic avalanches at control trenches, enhancing the reliability and stability of the semiconductor device during switching operations.
Implementation Method 1
a shield region of a second conductivity type extending: at least partially further along the vertical direction than bottoms of some of the trenches, wherein bottoms of at least the control trenches extend at least partially into the shield region
Data Source
AI summary
An IGBT includes a drift region of a first conductivity type, a plurality of trenches laterally confining both first type mesas having a respective source region and a respective body region and second type mesas. A shield region does for example not laterally overlap with the second type mesa, but only with the first type mesa.