RC-IGBT Trench Capacitance Differentiation for Voltage Undershoot
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a tradeoff between anode efficiency and switching ruggedness in reverse-conducting insulated-gate bipolar transistors (RC-IGBTs), where high switching ruggedness is needed for hard-switching applications but results in increased switching losses, and low switching ruggedness reduces forward-recovery voltage undershoot, which can interfere with neighboring IGBTs and damage gate driver circuitry.
Innovation Solution
The RC-IGBT design incorporates a semiconductor substrate with IGBT and diode regions featuring trenches that provide different capacitance densities, with the diode region having a lower capacitance density than the IGBT region, achieved by varying trench depth, spacing, and insulating layer thickness, to reduce forward-recovery voltage undershoot while maintaining switching ruggedness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trench electrodes are added to the diode region to improve switching ruggedness, then switching ruggedness is improved, but forward-recovery voltage increases
Solution Approach 1:
The patent applies different trench electrode configurations to different regions of the device. The IGBT region has densely spaced trenches for high switching ruggedness, while the diode region has sparsely spaced trenches that provide minimal switching ruggedness improvement but significantly reduce forward-recovery voltage. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The device is segmented into two distinct regions with different trench electrode densities: an IGBT region with high-density trenches and a diode region with low-density trenches. This segmentation allows each region to have optimized characteristics for its specific operational requirements, enabling the diode to have low forward-recovery voltage while the IGBT maintains high switching ruggedness.
2Reliability
If the anode region is highly doped to provide switching ruggedness, then switching ruggedness is improved, but switching losses increase
Solution Approach 1:
The patent implements local quality differentiation in the anode region by combining moderate doping with selective trench electrode placement. The sparsely spaced trenches in the diode region provide sufficient switching ruggedness for hard-switching applications while the moderate doping level keeps switching losses low, resolving the contradiction between ruggedness and energy loss.
3Loss of energy
If the anode region is lightly doped to reduce switching losses, then switching losses are reduced, but switching ruggedness decreases
Solution Approach 1:
The trench electrodes serve as an intermediary structure that compensates for the reduced doping level. The sparsely spaced trenches in the diode region provide the necessary switching ruggedness for hard-switching applications even with moderate doping, allowing the device to achieve low switching losses while maintaining adequate switching ruggedness through the intermediary trench structure.
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 achieves low anode efficiency and high switching ruggedness, reducing switching losses and forward-recovery voltage undershoot, thus addressing the tradeoff between efficiency and ruggedness in RC-IGBTs.
Implementation Method 1
the plurality of first trenches provides a first capacitance between the first trench electrodes and the semiconductor substrate in the IGBT region and the plurality of second trenches provides a second capacitance between the second trench electrodes and the semiconductor substrate in the diode region
Data Source
AI summary
According to an embodiment of a power semiconductor device, the device includes: a semiconductor substrate including an IGBT region having an IGBT and a diode region having a diode. The IGBT region includes a plurality of first trenches extending perpendicular to a first main surface of the semiconductor substrate. The diode region includes a plurality of second trenches extending perpendicular to the first main surface of the semiconductor substrate. An average lateral spacing between adjacent ones of the second trenches is greater than an average lateral spacing between adjacent ones of the first trenches. Additional power semiconductor device embodiments are described herein, as are corresponding methods of production.