Shielded-Gate IGBT Structure for Reduced Turning-Off 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 significant minority carrier storage and a tailing turning-off current.
Innovation Solution
The IGBT device incorporates gate trenches with alternating shielded gates and p-type body regions of varying doping concentrations, along with insulated and isolated gates, to facilitate rapid turn-off of current channels by adjusting threshold voltages and gate charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the IGBT device uses a conventional structure with uniform doping, then the manufacturing process is simple, but the hole injection efficiency is low and turning-off loss is high
Solution Approach 1:
The p-type body region is divided into multiple regions with different doping concentrations (first p-type body region with lower doping and second p-type body region with higher doping). This segmentation allows different regions to have different functions: the lower-doped region facilitates hole injection and reduces turning-off loss, while the higher-doped region provides structural support and carrier supply, thereby resolving the contradiction between reducing energy loss and maintaining structural simplicity.
Solution Approach 2:
Different regions of the p-type body are given different doping concentrations to optimize local performance. The first p-type body region adjacent to the n-type drift region has lower doping concentration to enhance hole injection efficiency and reduce minority carrier storage, while the second p-type body region has higher doping concentration to maintain structural integrity and provide adequate carrier supply, thus locally optimizing the device to reduce turning-off loss without excessive complexity.
2Strength
If the IGBT device has high hole injection efficiency, then the saturation voltage drop decreases, but the device structure becomes more complex with multiple p-type regions
Solution Approach 1:
The p-type body region is segmented into first and second p-type body regions with different doping concentrations. The first p-type body region with lower doping concentration is positioned adjacent to the n-type drift region to maximize hole injection efficiency, while the second p-type body region with higher doping concentration provides structural support. This segmentation achieves high hole injection efficiency without requiring complete redesign of the entire device structure.
Solution Approach 2:
The doping concentration is locally optimized in different body regions: the first p-type body region has lower doping concentration to enhance hole injection efficiency at the critical interface with the n-type drift region, while the second p-type body region maintains higher doping concentration for structural stability. This local quality differentiation achieves high hole injection efficiency with minimal structural complexity.
Data Source
AI summary
An IGBT device includes a p-type collector region, an n-type semiconductor layer located above the p-type collector region, a plurality of gate trenches, shielded gates, gates, and a p-type body region located in the n-type semiconductor layer and between adjacent gate trenches. The gate trenches are located in the n-type semiconductor layer. A shielded gate is located in a lower part of a gate trench. A gate is 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.