RC-IGBT Trench Structure for Lower Recovery Loss and Breakdown Control
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Solution Overview
Problem
Reverse recovery loss and avalanche breakdown issues in reverse-conducting IGBTs (RC-IGBTs) due to carrier injection and electric field concentration at pn junctions during reverse recovery operations, leading to potential damage and reduced safe operating areas.
Innovation Solution
The semiconductor device incorporates a pin diode structure with specific trench and semiconductor region configurations, including channel regions and anode regions with varying impurity concentrations, along with a trench gate electrode, to manage carrier flow and disperse avalanche breakdown, thereby reducing recovery loss and expanding the safe operating area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pin diode is used in RC-IGBT to enable reverse conduction, then reverse conduction capability is achieved, but recovery loss increases due to carrier injection into the drift region
Solution Approach 1:
The pin diode structure is segmented into multiple regions with different impurity concentrations: a first semiconductor region (n-type drift region) with lower impurity concentration and a second semiconductor region (p-type base region) with higher impurity concentration. This segmentation allows the device to maintain reverse conduction capability while reducing carrier injection into the drift region, thereby lowering recovery loss.
Solution Approach 2:
Different regions of the semiconductor device are assigned different impurity concentrations to optimize local performance. The first semiconductor region has a lower impurity concentration to reduce carrier injection and recovery loss, while the second semiconductor region has a higher impurity concentration to ensure proper diode operation. This local quality differentiation resolves the contradiction between enabling reverse conduction and minimizing recovery loss.
2Adaptability or versatility
If a pin diode is used in reverse recovery operation, then reverse conduction is enabled, but electric field concentration occurs at the pn junction causing avalanche breakdown
Solution Approach 1:
The semiconductor device employs local quality differentiation by creating regions with varying impurity concentrations. The first semiconductor region has a lower impurity concentration that reduces electric field concentration at the pn junction, preventing avalanche breakdown. The second semiconductor region has a higher impurity concentration to maintain proper diode functionality. This resolves the contradiction between enabling reverse conduction and preventing avalanche breakdown.
Solution Approach 2:
The invention changes the impurity concentration parameter across different regions of the semiconductor device. By setting the impurity concentration of the first semiconductor region to be lower than that of the second semiconductor region, the electric field distribution is modified to prevent concentration and avalanche breakdown, while still enabling reverse conduction capability.
3Loss of energy
If the impurity concentration in the drift region is increased to reduce recovery loss, then recovery loss decreases, but the breakdown voltage of the pin diode decreases
Solution Approach 1:
The invention applies local quality differentiation by creating two distinct semiconductor regions with different impurity concentrations. The first semiconductor region has a lower impurity concentration to maintain high breakdown voltage, while the second semiconductor region has a higher impurity concentration to reduce carrier injection and recovery loss. This resolves the contradiction between reducing recovery loss and maintaining breakdown voltage.
Solution Approach 2:
The pin diode structure is segmented into a first semiconductor region with lower impurity concentration (maintaining breakdown voltage) and a second semiconductor region with higher impurity concentration (reducing recovery loss). This segmentation allows the device to simultaneously achieve low recovery loss and high breakdown voltage, resolving the contradiction between these two parameters.
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
The proposed structure effectively reduces recovery loss and suppresses damage from avalanche breakdown, enhancing the reverse recovery safe operating area and improving the overall performance of RC-IGBTs.
Implementation Method 1
a recovery current flows in the reverse direction to discharge the carriers injected into the drift region
Implementation Method 2
electric field concentration may occur at a specific location of the pn junction to cause avalanche breakdown
Data Source
AI summary
A semiconductor device of embodiments includes: a semiconductor layer including a first trench, a second trench, a first semiconductor region of a first conductive type, a second semiconductor region of a second conductive type provided between a first face and the first semiconductor region, between the first trench and the second trench, and in contact with the second trench, a third semiconductor region of a first conductive type provided between the first trench and the second semiconductor region, a fourth semiconductor region of a second conductive type provided between the third semiconductor region and the first face, and a fifth semiconductor region of a second conductive type provided between the second semiconductor region and the first face, spaced from the fourth semiconductor region, in contact with the second trench; a first electrode on a first face side; and a second electrode on a second face side.