RC IGBT Diode Mesa Structure for Reverse Current Control
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Solution Overview
Problem
Existing RC IGBTs lack high controllability, particularly in controlling the reverse conducting state, which can lead to unsafe and inefficient operation.
Innovation Solution
The RC IGBT design integrates a diode section and an IGBT section monolithically within the same chip, with specific trench and mesa configurations that enhance control over both forward and reverse load currents, ensuring the diode section operates independently of control signals and has a larger lateral extension relative to the IGBT section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate diode is connected anti-parallel to a regular IGBT to provide reverse current capability, then the reverse conducting state is achieved, but the device complexity increases and controllability is reduced
Solution Approach 1:
The patent merges the IGBT and diode functions into a single monolithic integrated structure. The semiconductor body contains both IGBT cells with gate-controlled channels and diode cells without gate control, allowing both forward and reverse current capabilities to be achieved in one device without requiring a separate anti-parallel diode connection.
Solution Approach 2:
The integrated RC IGBT structure provides multiple functions within a single device: it can conduct forward load current through the IGBT section with gate control, conduct reverse load current through the diode section automatically, and maintain controllability through the gate electrode structure. This multi-functionality eliminates the need for separate components.
2Device complexity
If the diode section and IGBT section are monolithically integrated within the same chip, then the device complexity is reduced, but the controllability of reverse conducting state may be compromised
Solution Approach 1:
The semiconductor body is segmented into distinct IGBT cells and diode cells. The IGBT cells include gate electrodes and controlled channels for controllable conduction, while the diode cells lack gate control structures and conduct automatically in reverse bias. This segmentation allows each section to perform its specific function with appropriate controllability characteristics.
Solution Approach 2:
Different regions of the semiconductor body are designed with different structural qualities: the IGBT section has gate electrodes and insulated gate structures for controllable operation, while the diode section has a simpler pn-junction structure without gate control for automatic reverse conduction. Each local region is optimized for its specific function.
3Reliability
If the diode emitter region has a lateral extension of at least 50% of the drift region thickness, then the reverse conducting capability is enhanced, but the overlap with IGBT section increases
Solution Approach 1:
The diode emitter region is designed with an asymmetric lateral extension that is at least 50% of the drift region thickness, creating an unequal distribution of conducting areas between the IGBT and diode sections. This asymmetric design optimizes the reverse conducting capability while managing the overlap effects through the specific geometric configuration.
Data Source
AI summary
A semiconductor device includes a diode section. At least some of a plurality of diode mesas in the diode section are coupled to the drift region via a second anode region electrically connected to the emitter terminal of the semiconductor device. The second anode region extends deeper along the vertical direction as compared to trenches in the diode section.