Power Transistor With Tapered Mesas and Segmented Gates
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Solution Overview
Problem
Power semiconductor transistors, such as IGBTs, face challenges in minimizing switching losses and achieving dV/dt controllability while maintaining high efficiency and efficiency in modern applications like automotive and industrial systems.
Innovation Solution
The design incorporates a semiconductor body with a drift region, power unit cells featuring control trenches, active mesas, and a semiconductor barrier region of the second conductivity type, where the barrier region overlaps significantly with the active mesa and further trenches, allowing for enhanced control over the load current and voltage slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching duration is reduced to minimize switching losses, then switching losses decrease, but dV/dt controllability becomes difficult to maintain
Solution Approach 1:
The gate electrode is divided into multiple independently controllable segments (first gate electrode and second gate electrode) positioned at different locations within the trench. This segmentation allows separate control of different regions of the semiconductor device, enabling independent optimization of switching speed in one region while maintaining dV/dt controllability in another region through coordinated gating signals.
Solution Approach 2:
The gate electrode is extended into the vertical dimension by positioning it within a trench structure that penetrates through the semiconductor layers. This three-dimensional arrangement allows the gate to control multiple regions at different depths and lateral positions, providing additional degrees of freedom for optimizing both switching performance and voltage slope control that cannot be achieved with planar gate structures.
2Loss of energy
If switching duration is reduced to minimize switching losses, then switching losses decrease, but turn-on and turn-off durations increase
Solution Approach 1:
The multi-segment gate electrode structure enables staged or periodic activation of different gate regions during the switching transition. By sequentially or differentially activating gate segments, the switching process can be optimized to reduce energy losses during critical transitions while managing the overall duration through coordinated timing of gate signals applied to different segments.
3Device complexity
If a single gate electrode is used, then device structure is simple, but dV/dt controllability and switching performance cannot be simultaneously optimized
Solution Approach 1:
The gate electrode is divided into multiple independently controllable segments (first gate electrode and second gate electrode) positioned at different locations within the trench. This segmentation allows separate control of different regions of the semiconductor device, enabling independent optimization of switching speed in one region while maintaining dV/dt controllability in another region through coordinated gating signals.
Solution Approach 2:
The multi-segment gate electrode structure serves multiple functions simultaneously: it provides voltage control for switching, controls dV/dt through distributed capacitance, and enables independent optimization of different performance parameters. Each gate segment can be independently biased to achieve different operational modes, making the structure universally applicable for optimizing various performance aspects.
Data Source
AI summary
A power transistor having a semiconductor barrier region is presented. A power unit cell of the power transistor has at least two trenches that may both extend into the semiconductor barrier region. The semiconductor barrier region may be p-doped and vertically confined, i.e., in and against the extension direction, by the drift region. The semiconductor barrier region can be electrically floating. Further, the at least two trenches may both increase in width along their respective extension into the semiconductor body.