Trench Gate MOS Semiconductor Device Reverse Breakdown Control
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Solution Overview
Problem
Existing reverse blocking IGBTs face issues with lower reverse breakdown voltage compared to forward breakdown voltage, leading to oscillation of voltage and current waveforms during turn-off and reverse recovery, which can cause noise and potential device damage.
Innovation Solution
The semiconductor device incorporates a shell region with a higher impurity concentration than the drift region, positioned between the base and drift regions, and a trench gate MOS structure to control the depletion layer and electric field distribution, ensuring the depletion layer does not reach the shell region during reverse voltage application, thereby improving both forward and reverse breakdown voltages and reducing oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the depletion layer reaches the shell region during reverse voltage application, then reverse breakdown voltage increases, but oscillation of voltage and current waveforms occurs
Solution Approach 1:
The shell region is pre-configured with higher impurity concentration before reverse voltage application. This preliminary structural arrangement ensures that when reverse voltage is applied, the depletion layer has a controlled termination point at the shell region boundary, preventing uncontrolled breakdown while avoiding waveform oscillation through proper impurity concentration design.
Solution Approach 2:
The patent carefully controls the impurity concentration parameter of the shell region (higher than drift region but within specific ranges) to achieve optimal balance between reverse breakdown voltage and waveform stability. The trench gate structure also modifies the electric field distribution parameter to prevent depletion layer penetration into the shell region under normal operating conditions.
2Stability of the object's composition
If the depletion layer is controlled not to reach the shell region, then waveform oscillation is suppressed, but reverse breakdown voltage may be limited
Solution Approach 1:
The shell region acts as an intermediary structure between the base region and drift region. It provides a controlled interface that allows the depletion layer to terminate at a specific location (at the shell region boundary) rather than penetrating deeper, thereby mediating between the requirements for waveform stability and reverse breakdown voltage enhancement.
Solution Approach 2:
The patent segments the drift region by introducing the shell region with different impurity characteristics. This segmentation creates distinct functional zones: the drift region handles forward conduction and initial reverse depletion, while the shell region provides a controlled termination boundary that enhances reverse breakdown voltage without causing instability.
3Reliability
If a shell region with higher impurity concentration is introduced, then reverse breakdown voltage is enhanced, but device structure becomes more complex
Solution Approach 1:
The patent combines the shell region formation with the existing trench gate MOS structure fabrication process. The shell region is created as part of the same diffusion or implantation steps that form the base and drift regions, merging multiple functions into a single integrated structure rather than adding separate components.
Solution Approach 2:
The shell region serves multiple functions simultaneously: it enhances reverse breakdown voltage, controls depletion layer termination, and works in conjunction with the trench gate structure to suppress waveform oscillation. This multi-functionality reduces the need for additional separate structures or components.
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 configuration enhances the reverse and forward breakdown voltages, suppresses oscillation of voltage and current waveforms during turn-off and reverse recovery, and facilitates faster recovery of blocking voltage, preventing noise and device damage.
Implementation Method 1
The drift region has sufficient resistivity to prevent a depletion layer, which is spread from the collector region when a reverse rated voltage is applied using the emitter electrode as a positive electrode, from reaching one of the shell region and the bottom of the trench which is closer to the collector region than the other
Implementation Method 2
The shell region has a higher impurity concentration than the drift region... ensuring the depletion layer does not reach the shell region during reverse voltage application, thereby improving both forward and reverse breakdown voltages
Implementation Method 3
A trench that extends from the one main surface of the semiconductor substrate to the drift region through the emitter region and the base region is provided. An insulating film is provided along an inner wall of the trench. A gate electrode is provided in the trench through the insulating film.
Data Source
AI summary
A trench gate MOS structure is provided on one main surface of a semiconductor substrate which will be an n− drift region. An n shell region is provided in the n− drift region so that it contacts a surface of a p base region close to the n− drift region forming the trench gate MOS structure. The n shell region has a higher impurity concentration than the n− drift region. The effective dose of n-type impurities in the n shell region is equal to or less than 5.0×1012 cm−2. The n− drift region has a resistivity to prevent a depletion layer, which is spread from a p collector region on the other main surface when reverse rated voltage is applied with an emitter as positive electrode, from reaching either n shell region or the bottom of a first trench, whichever is closer to the p collector region.