Shielded-Gate IGBT Structure for Faster Turn-Off
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Solution Overview
Problem
The IGBT device suffers from high turning-off loss due to low hole injection efficiency at the p-type body region and n-type drift region interface, leading to significant minority carrier storage and a tailing turning-off current.
Innovation Solution
The IGBT device incorporates a p-type collector region, n-type semiconductor layer, p-type body regions with varying doping concentrations, gate trenches with shielded gates, and a gate structure that connects to different voltages, allowing for differential 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
An IGBT device includes an p-type collector region, 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.