IGBT Buffer Region Doping Profile for Stable Switching Voltage
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Solution Overview
Problem
Existing semiconductor devices with insulated gate bipolar transistors (IGBTs) face issues with voltage oscillation and switching loss due to rapid expansion of the depletion layer and carrier recombination, which are not effectively managed by current buffer region designs.
Innovation Solution
A semiconductor device with a buffer region having specific impurity concentration peaks and controlled carrier lifetime distributions is introduced, where the impurity concentration is varied stepwise to slow down the depletion layer expansion and manage carrier recombination, thereby stabilizing the voltage waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer region with higher impurity concentration than the drift layer is provided between the drift layer and collector electrode, then the device can manage carrier recombination, but voltage oscillation occurs due to rapid depletion layer expansion
Solution Approach 1:
The buffer region is segmented into multiple zones with different impurity concentrations (first buffer region with concentration N1, second buffer region with concentration N2 where N1 < N2). This segmentation creates a gradient that controls the depletion layer expansion rate, preventing rapid expansion and voltage oscillation while maintaining effective carrier recombination management.
Solution Approach 2:
Different regions of the buffer are given different local properties through varying impurity concentrations. The first buffer region has lower impurity concentration to slow depletion layer expansion, while the second buffer region has higher impurity concentration to enhance carrier recombination. This local differentiation resolves the contradiction between voltage stability and carrier management.
2Stability of the object's composition
If impurity concentration is increased in the buffer region to reduce voltage oscillation, then voltage waveform stability improves, but switching loss increases due to enhanced carrier recombination
Solution Approach 1:
The buffer region is divided into two segments with different impurity concentrations. The first buffer region (lower concentration) minimizes carrier recombination to reduce switching loss, while the second buffer region (higher concentration) provides voltage waveform stability. This segmentation allows both requirements to be satisfied simultaneously in different zones.
Solution Approach 2:
The impurity concentration parameter is changed spatially across the buffer region, creating a gradient from lower concentration (first buffer region) to higher concentration (second buffer region). This parameter variation enables the system to achieve both low switching loss and voltage stability by optimizing the concentration at different locations.
3Device complexity
If a simple buffer region structure is used, then device complexity is reduced, but voltage oscillation and switching loss cannot be effectively managed
Solution Approach 1:
The buffer region is segmented into two functional zones with different impurity concentrations, providing both voltage waveform control and switching loss management capabilities while maintaining a relatively simple overall structure. This segmentation achieves enhanced functionality without excessive complexity.
Solution Approach 2:
Different local regions of the buffer are assigned different impurity concentrations to perform different functions: the first buffer region focuses on voltage stability while the second buffer region focuses on carrier recombination management. This local quality differentiation enables effective management of voltage and switching loss with a straightforward structural approach.
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 design reduces voltage oscillation amplitude and switching loss by controlling the depletion layer expansion and carrier recombination, enhancing the device's operational stability and efficiency.
Implementation Method 1
rapid expansion of the depletion layer
Implementation Method 2
carrier recombination
Data Source
AI summary
A semiconductor device of an embodiment includes a semiconductor substrate that includes a first principal surface and a second principal surface, the first principal surface and the second principal surface facing each other in a first direction, a drift region, a buffer region that includes a plurality of concentration peaks, a first electrode provided on the first principal surface, a second electrode provided on the second principal surface, and a transistor region, in which the plurality of concentration peaks includes a first concentration peak that is disposed closest to the second principal surface, a second concentration peak that is disposed farther from the second principal surface than the first concentration peak and has a higher impurity concentration than that of the first concentration peak, and a third concentration peak that is selectively providedbetween the first principal surface and the second concentration peak.