IGBT Mesa Trench Control for Loss Reduction
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Solution Overview
Problem
Power semiconductor devices face challenges in minimizing conduction and switching losses while maintaining easy controllability, particularly in ensuring the rate of change of voltage during turn-on or turn-off operations does not exceed predetermined maximum values.
Innovation Solution
The power semiconductor device incorporates a semiconductor body with a drift region and multiple cells, each comprising a mesa structure and a trench structure with a control electrode, where the first mesa is configured to fully deplete the channel region of mobile charge carriers in the conducting state and induce a current path for the first conductivity type, while the second mesa controls the load current through a conductive channel, and a guidance zone and barrier zone are used to manage charge carrier flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the channel region is made narrow (less than 100 nm lateral extension) to reduce conduction losses, then the device can be fully depleted of mobile charge carriers, but the controllability of voltage change rate becomes difficult to maintain
Solution Approach 1:
The device is divided into multiple independent cells, each with its own mesa structure and control electrode. This segmentation allows each cell to be fully depleted individually while maintaining overall device controllability through coordinated control of multiple cells.
Solution Approach 2:
The invention transitions from planar control to three-dimensional control by introducing control electrodes that extend into trenches beneath the mesa structures. This vertical dimension allows for precise control of the depletion region in the narrow channel while maintaining ease of operation through electrostatic field management.
2Loss of energy
If high switching speeds are used to reduce switching losses, then efficiency improves, but the rate of change of voltage (dV/dt) exceeds predetermined maximum values
Solution Approach 1:
The control electrodes in the trenches can dynamically adjust the electric field distribution during switching transitions. By modulating the voltage on these control electrodes, the depletion region can be expanded or contracted in a controlled manner, enabling fast switching while limiting dV/dt to predetermined maximum values.
Solution Approach 2:
The multiple control electrodes provide a mechanism for feedback control during switching operations. The voltage distribution among the control electrodes can be adjusted based on the switching state to maintain the voltage change rate within specified limits while achieving low switching losses.
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 configuration reduces conduction and switching losses, enhances controllability, and effectively manages charge carrier flow to prevent excessive voltage change during operations, thereby improving the performance of power semiconductor devices.
Implementation Method 1
the forward voltage may induce a depletion region at a junction formed by a transition between the channel region and a drift region of the power semiconductor device, wherein the depletion region is also called 'space charge region' and may mainly expand into the drift region of the semiconductor device
Implementation Method 2
the control electrode may be provided with a control signal having a voltage within a first range so as to induce a load current path within the channel region
Data Source
AI summary
A power semiconductor device has a semiconductor body coupled to first and second load terminal structures, the semiconductor body configured to conduct a load current during a conducting state of the device and having a drift region. The power semiconductor device includes a plurality of cells, each cell having: a first mesa in a first cell portion, the first mesa including: a first port region, and a first channel region, the first mesa exhibiting a total extension of less than 100 nm in a lateral direction, and a second mesa in a second cell portion including: a second port region, and a second channel region. A trench structure includes a control electrode structure configured to control the load current by inversion or accumulation. A guidance zone of the second conductivity type is below the second channel region and is displaced from the first and the second channel regions.