Reverse Conducting IGBT Segmentation for Latch-up and Switching Trade-offs
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Solution Overview
Problem
Reverse conducting IGBTs with monolithically integrated free-wheeling diodes face high reverse current peaks and switching-off energy due to flooding of the base region with minority charge carriers, which increases power loss in forward mode.
Innovation Solution
The semiconductor device incorporates a reverse conducting IGBT structure with a high-doping anti-latch-up region and a separate diode-cell with a lower doping anode region, reducing minority charge carrier lifetime and optimizing latch-up robustness and switching performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a highly doped anti-latch-up region is provided in the body region to ensure latch-up robustness, then latch-up stability is improved, but the base region floods with minority charge carriers in reverse mode, increasing reverse current peak and switching-off energy
Solution Approach 1:
The device is divided into two separate cells: an IGBT-cell containing the anti-latch-up region for reliability, and a diode-cell without anti-latch-up region for efficient reverse conduction. This segmentation allows each cell to be optimized for its specific function without compromising the other.
Solution Approach 2:
The anti-latch-up region is localized only to the IGBT-cell where it is needed for latch-up prevention, while the diode-cell maintains a simple structure without anti-latch-up doping. This local differentiation enables the diode-cell to conduct reverse current efficiently without excessive minority charge carrier storage.
2Device complexity
If a monolithically integrated free-wheeling diode is provided, then external inductances and capacitances are avoided, but reverse current peak and switching-off energy become too high for hard-switching applications
Solution Approach 1:
The monolithically integrated device is segmented into two functional cells with different structures: the IGBT-cell with anti-latch-up region for stability, and the diode-cell without anti-latch-up region for efficient reverse conduction. This resolves the contradiction between integration benefits and switching performance.
Solution Approach 2:
The diode-cell is designed with local quality differences from the IGBT-cell, specifically the absence of anti-latch-up doping, enabling efficient reverse conduction with low switching-off energy while maintaining the benefits of monolithic integration.
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 design reduces the flooding of the base region with minority charge carriers, lowering reverse current peaks and switching-on energy, making it more suitable for hard-switching applications while maintaining latch-up stability in forward mode.
Implementation Method 1
an anti-latch-up region of the second conductivity type in ohmic contact with the first electrode and with a maximum doping concentration which is higher than a maximum doping concentration of the body region
Data Source
AI summary
A semiconductor device is provided which includes a semiconductor body having a base region and a main horizontal surface, and a first electrode arranged on the main horizontal surface. The semiconductor body further includes a plurality of vertical trenches having gate electrodes in a vertical cross-section. A body region forms a first pn-junction with the base region and extends between two of the vertical trenches. A source region is in ohmic contact with the first electrode and arranged between the two vertical trenches. An anti-latch-up region is arranged between the two vertical trenches and in ohmic contact with the first electrode. The anti-latch-up region has a maximum doping concentration which is higher than a maximum doping concentration of the body region. An anode region forms a rectifying pn-junction with the base region only and adjoins a third one of the vertical trenches, and has ohmic contact with the first electrode.