Multi-Trench Bipolar Device for Low Turn-Off Loss
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Solution Overview
Problem
Conventional bipolar semiconductor devices face challenges in achieving low on-state voltage drop (VON) while minimizing turn-off losses (EOFF) and turn-off delay time (Td,OFF), as desirable on-state characteristics often result in increased EOFF and longer Td,OFF, especially during fast switching.
Innovation Solution
The implementation of a bipolar semiconductor device with multi-trench enhancement regions, where N-type enhancement regions are localized in the N-type drift region, extending between depletion trenches and control trenches, but not between adjacent control trenches, reducing charge and Miller capacitance, thereby enhancing conductivity modulation and reducing EOFF and Td,OFF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional techniques are used to achieve low on-state voltage drop, then on-state characteristics are improved, but turn-off delay time increases
Solution Approach 1:
The enhancement region is segmented by depletion trenches, which interrupt the continuous charge storage path. This segmentation reduces the total stored charge that must be removed during turn-off, thereby reducing turn-off delay time while maintaining the low on-state voltage drop provided by the enhancement regions.
Solution Approach 2:
The patent extracts or removes portions of the enhancement region by introducing depletion trenches that deplete carriers in those areas. This extraction reduces the excess charge storage that causes delay during turn-off, while retaining enough enhancement region to maintain low on-state voltage drop.
2Reliability
If enhancement regions extend between adjacent control trenches, then conductivity modulation is improved, but charge storage increases leading to higher turn-off losses
Solution Approach 1:
The enhancement region is segmented into discrete portions separated by depletion trenches rather than forming a continuous structure. This segmentation maintains conductivity modulation benefits where enhancement regions are present while preventing excessive charge storage that would occur with continuous enhancement regions extending between all control trenches.
Solution Approach 2:
The patent applies enhancement regions selectively in specific locations to improve conductivity modulation where needed, while using depletion trenches in other locations to limit charge storage. This local quality differentiation optimizes the balance between conductivity modulation and turn-off losses.
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 effectively reduces turn-off losses and delay time while maintaining desirable on-state voltage drop, and improves conductivity modulation, especially in ultra-narrow unit cell pitches, outperforming conventional devices like IGBTs.
Implementation Method 1
enhancing conductivity modulation by a bipolar semiconductor device
Data Source
AI summary
There are disclosed herein various implementations of a bipolar semiconductor device with multi-trench enhancement regions. Such a bipolar semiconductor device includes a drift region having a first conductivity type situated over an anode layer having an opposite, second conductivity type. The device also includes a first control trench extending through an inversion region having the second conductivity type, and further extending into the drift region, the first control trench being adjacent to cathode diffusions. In addition, the device includes first and second depletion trenches, each having a depletion electrode, the first depletion trench being situated between the second depletion trench and the first control trench. An enhancement region having the first conductivity type is localized in the drift region and extends from the first control trench to the first second depletion trench and further from the first depletion trench to the second depletion trench.