Shielded-Gate IGBT Structure for Faster Turn-Off and Lower Loss
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Solution Overview
Problem
The IGBT device experiences high turning-off loss due to low hole injection efficiency at the p-type body region and n-type drift region interface, leading to a significant tailing turning-off current and increased saturation voltage drop.
Innovation Solution
The IGBT device incorporates a p-type collector region, n-type semiconductor layer, p-type body regions with varying doping concentrations, a gate trench with a shielded gate structure, and an n-type emitter electrode region, where the shielded gate is connected to either the gate voltage or emitter electrode voltage, optimizing the threshold voltages and gate charges to facilitate rapid turn-off of current channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional IGBT device structure is used, then the device can achieve basic switching functionality, but the hole injection efficiency at the p-type body region and n-type drift region interface is low, causing high saturation voltage drop
Solution Approach 1:
The patent introduces a first p-type body region with a first doping concentration and a second p-type body region with a second doping concentration (different from the first) in the n-type semiconductor layer. This local quality differentiation optimizes the hole injection efficiency at the interface between the p-type body region and n-type drift region, thereby reducing the saturation voltage drop while maintaining reliable switching functionality.
2Reliability
If a conventional IGBT device structure is used, then the device can operate with standard gate control, but a large number of minority carriers are stored in the n-type drift region, causing serious tailing turning-off current and large turning-off loss
Solution Approach 1:
The patent divides the gate control into two independent parts: a gate electrode and a shielded gate electrode. The gate electrode controls the main current channel, while the shielded gate electrode, when activated, rapidly removes minority carriers from the n-type drift region. This segmentation allows independent optimization of turn-off speed and energy loss by controlling the shielded gate timing.
Solution Approach 2:
The shielded gate electrode is designed to be activated before the main gate electrode during the turn-off process. By applying a negative voltage to the shielded gate electrode first, minority carriers are rapidly removed from the n-type drift region in advance, preventing the tailing turning-off current and reducing turning-off loss when the main gate electrode is subsequently deactivated.
Data Source
AI summary
Provided is an IGBT device belonging to the technical field of semiconductor power devices. The IGBT device includes an n-type semiconductor layer, several p-type body regions located in the n-type semiconductor layer, a gate trench located in the n-type semiconductor layer and between adjacent p-type body regions, a gate trench located in the n-type semiconductor layer and between adjacent p-type body regions, a shielded gate located in a lower part of the gate trench, and a gate located in an upper part of the gate trench. The gate, the shielded gate, and the n-type semiconductor layer are insulated and isolated from each other. Among the several p-type body regions, at least one p-type body region has a first doping concentration and is defined as a first p-type body region, and at least one p-type body region has a second doping concentration and is defined as a second p-type body region. The first doping concentration of the first p-type body region is smaller than the second doping concentration of the second p-type body region. At least one shielded gate in at least one gate trench adjacent to the first p-type body region is externally connected to a gate voltage. A shielded gate in a gate trench other than the at least one gate trench where the at least one shielded gate externally connected to the gate voltage is located is externally connected to an emitter electrode voltage.