IGBT Gate Electrode Segmentation for Surge Voltage Control
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Solution Overview
Problem
Semiconductor devices with IGBT elements face increased surge voltage during turn-on due to rapid gate voltage increase, which can lead to device destruction, despite effective surge voltage reduction during turn-off.
Innovation Solution
The semiconductor device incorporates a structure where the emitter layer is in contact with only the gate insulation layers of the normal gate electrodes, preventing electron supply when the control gate electrodes exceed the threshold voltage, thereby controlling turn-on with a slower rate of gate voltage increase, and utilizing resistors to manage gate voltage changes to reduce surge voltage during both turn-on and turn-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gate voltage of the remainder of the gate electrodes increases rapidly to turn on the IGBT element, then the turn-on speed is improved, but the surge voltage becomes large enough to destroy the IGBT element
Solution Approach 1:
The gate electrodes are divided into two groups: normal gate electrodes connected through first resistors and control gate electrodes connected through second resistors with smaller resistance. This segmentation allows differential control of gate voltage rise rates, enabling the control gate electrodes to pre-establish conductive channels while the normal gate electrodes maintain slower voltage increase to limit surge voltage during turn-on
Solution Approach 2:
The control gate electrodes are activated in advance before the normal gate electrodes during turn-on. By applying turn-on voltage to the control gate electrodes first through the lower-resistance second resistors, conductive channels are preliminarily established in the drift layer, allowing subsequent current flow to occur at lower surge voltage when the normal gate electrodes are activated
2Speed
If the gate voltage of the gate electrodes decreases rapidly to turn off the IGBT element, then the turn-off speed is improved, but the surge voltage at turn-off increases
Solution Approach 1:
The gate electrodes are segmented into normal and control groups with different resistor connections, allowing the control gate electrodes to maintain higher gate voltage longer during turn-off. This creates a time delay where control gate electrodes continue supplying carriers to the drift layer even as normal gate electrodes voltage drops, thereby suppressing turn-off surge voltage while maintaining acceptable turn-off speed
Solution Approach 2:
The resistors act as intermediary elements that control the rate of voltage change on different gate electrode groups. The first resistors connected to normal gate electrodes have higher resistance to slow down voltage decrease, while second resistors connected to control gate electrodes have lower resistance, creating a controlled differential decay that prevents surge voltage during turn-off
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 approach reduces surge voltage during turn-on while maintaining reduced surge voltage during turn-off, preventing current concentration that could destroy the IGBT element by controlling electron and hole supply evenly across the drift layer.
Implementation Method 1
a predetermined voltage is applied to a part of the gate electrodes through a first resistor and applied to a remainder of the gate electrodes through a second resistor having a resistance smaller than that of the first resistor
Data Source
AI summary
A semiconductor device includes a first conductivity-type drift layer, a second conductivity-type base layer formed in a front surface portion of the drift layer, a second conductivity-type collector layer formed in the drift layer and separated from the base layer, gate insulation layers formed on a surface of the base layer, gate electrodes individually formed on the gate insulation layers, an emitter layer formed in a front surface portion of the base layer, an emitter electrode electrically connected to the emitter layer and the base layer, and a collector electrode electrically connected to the collector layer. A rate of change in a gate voltage of a part of the gate electrodes is smaller than a rate of change in a gate voltage of a remainder of the gate electrodes. The emitter layer is in contact with only the gate insulation layers provided with the part of the gate electrodes.