CIGBT Trench Structure for Low Forward Voltage
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving optimal trade-offs between on-state and turn-off losses in high-power applications, particularly in trench IGBTs, where forward voltage drops are high and switching losses are significant.
Innovation Solution
The development of a Clustered Insulated Gate Bipolar Transistor (CIGBT) with a trench structure that includes 'dummy cells' and 'dummy trenches' to improve the trade-off between on-state and turn-off losses, where the trenches intersect specific semiconductor regions and are configured with insulating films and gate electrodes to control current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If trench IGBT structure is used, then switching performance is improved, but forward voltage drop increases
Solution Approach 1:
The device is divided into multiple cathode cells arranged in a cluster configuration, with each cell containing a trench structure. This segmentation allows the device to achieve low forward voltage drop through the clustered arrangement while maintaining the switching performance benefits of the trench structure in each individual cell.
Solution Approach 2:
Different regions of the device have optimized structures: the cathode cells contain trench structures for improved switching, while the clustered arrangement and dummy cells provide low forward voltage drop paths. The insulating films and gate electrodes are locally positioned to control current flow in specific regions, creating optimal local conditions for both switching performance and conduction loss reduction.
2Loss of energy
If dummy cells and dummy trenches are added, then trade-off between on-state and turn-off losses is improved, but device complexity increases
Solution Approach 1:
The device includes operational cathode cells and dummy cells arranged in a clustered configuration. The dummy cells and dummy trenches are segmented into specific positions within the cluster to optimize the balance between on-state and turn-off losses without requiring complete restructuring of the entire device.
Solution Approach 2:
The dummy cells and dummy trenches serve multiple functions: they improve the trade-off between on-state and turn-off losses, provide structural symmetry to the device, and maintain electrical field distribution. This multi-functionality justifies the additional complexity by delivering multiple performance benefits simultaneously.
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 CIGBT structure demonstrates significantly low forward voltage drops and improved trade-offs between on-state and turn-off losses, enhancing performance in high-power applications such as HVDC inverter systems and traction drive controls.
Implementation Method 1
a gate electrode provided in a trench through an insulating film... A flow of a current between the first and second main electrodes when a voltage of a predetermined direction is applied between these electrodes is controllable in accordance with a voltage applied to the gate electrode
Implementation Method 2
A depleted region extends from a junction between the first and the second semiconductor regions reaching the trench
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
A clustered Insulated Gate Bipolar Transistor (CIGBT) comprising a drift region (24), a P well region (20) formed within the n-type drift region, an N well region (22) formed within the P well region (20), a P base region (32) formed within the N well region (22) and a cathode region (36). One or more trenches (40) are formed in the device and configured to longitudinally intersect the drift region (24) and, optionally, the P well region (20) as well as laterally intersecting the base region (32), the N well region (22) and the P well region (20). An insulating film is formed on the inner surface of the trenches (40) and gate oxide is formed on the insulating film so as to substantially fill the trenches and form a gate.