Bipolar Semiconductor Device Sub-Cathode Enhancement Regions
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Solution Overview
Problem
Conventional bipolar semiconductor devices, such as IGBTs, face challenges in achieving low on-state voltage drop (VON) while minimizing turn-off losses (EOFF) and turn-off delay time (Td,OFF) during fast switching, as desirable on-state characteristics often result in increased EOFF and longer Td,OFF.
Innovation Solution
The implementation of bipolar semiconductor devices with sub-cathode enhancement regions, where N-type enhancement regions are localized between control trenches and depletion trenches, reducing charge in the drift region and minimizing Miller capacitance, thereby enhancing the rapid expansion of the depletion region during turn-off 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 sub-cathode enhancement regions provide localized carrier generation capability at the cathode interface, enabling faster turn-off response in the critical region near the cathode without affecting the overall on-state voltage drop characteristics of the device.
Solution Approach 2:
The enhancement regions are pre-formed during device fabrication with appropriate doping concentrations, so that during turn-off operation, carriers are immediately available in the sub-cathode region to accelerate depletion region expansion and reduce turn-off delay time.
2Speed
If switching speed is increased, then switching performance is improved, but switching losses increase
Solution Approach 1:
The patent changes the doping concentration parameter in the drift region by introducing sub-cathode enhancement regions with doping concentrations of 1×10^15 to 1×10^16 atoms/cm³. This parameter change enables faster carrier generation and depletion region expansion during turn-off, allowing high switching speeds with reduced switching 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 a desirable on-state voltage drop, outperforming conventional devices by allowing faster switching and lower power losses.
Implementation Method 1
minimizing Miller capacitance, thereby enhancing the rapid expansion of the depletion region during turn-off
Data Source
AI summary
There are disclosed herein various implementations of a bipolar semiconductor device with sub-cathode enhancement regions. Such a bipolar semiconductor device includes a drift region having a first conductivity type situated over an anode layer having a second conductivity type opposite the first conductivity type. The bipolar semiconductor device also includes first and second depletion trenches, each having a depletion electrode. In addition, the bipolar semiconductor device includes a first control trench situated between the first and second depletion trenches, the first control trench extending into the drift region and being adjacent to cathode diffusions. An enhancement region having the first conductivity type is localized in the drift region between the first control trench and one or both of the first and second depletion trenches. In one implementation, the bipolar semiconductor device may be an insulated-gate bipolar transistor (IGBT).