Super Junction IGBT Structure for Lower Turn-Off Tail Current
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Solution Overview
Problem
Conventional super junction IGBT devices experience large turn-off energy losses due to tail currents during the turn-off stage, which hinder their application in high-frequency power electronic devices.
Innovation Solution
The IGBT device incorporates a drift region with pillar regions and transition layers of specific doping types and thicknesses, including a first and second transition layer with controlled doping concentrations, to manage excess carriers and minimize tail currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional super junction IGBT structure is used, then high blocking voltage and low leakage current are achieved, but large tail current and large turn-off energy loss occur
Solution Approach 1:
The drift region is segmented into multiple regions with different doping types arranged in a super junction structure, creating alternating n-type and p-type pillar regions. This segmentation allows for better control of carrier distribution and reduces tail current during turn-off, thereby reducing turn-off energy loss while maintaining high blocking voltage capability.
Solution Approach 2:
Different regions of the device are given different doping concentrations and types to optimize local performance. The n-type drift region has specific doping concentration (1×10^16 to 1×10^18 atoms/cm³) while p-type pillar regions have different doping (1×10^18 to 1×10^20 atoms/cm³), creating local quality variations that control carrier behavior and reduce turn-off losses.
2Speed
If super junction drift region is used, then high withstand voltage and low loss are achieved, but slow space electric field establishment speed occurs during turn-off
Solution Approach 1:
The device structure is designed with pre-configured n-type and p-type pillar regions that prepare the charge distribution in advance. During turn-off, the space electric field can be established more quickly because the doping structure is already in place, reducing the time required for field establishment and consequently reducing turn-off energy loss.
Solution Approach 2:
The doping concentration parameters are optimized to achieve the right balance between field establishment speed and voltage blocking capability. The n-type drift region doping (1×10^16 to 1×10^18 atoms/cm³) and p-type pillar doping (1×10^18 to 1×10^20 atoms/cm³) are specifically chosen to enable faster field establishment while maintaining high voltage capability.
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 optimized structure reduces turn-off losses by precisely controlling excess carriers, improving the device's performance and making it suitable for high-frequency applications.
Implementation Method 1
Constrained by the conductivity modulation effect of the bipolar device, the space electric field establishment speed of the above-mentioned super junction IGBT is slow during the turn-off process
Data Source
AI summary
An IGBT device includes a drift region of a first doping type; a plurality of pillar regions of the second doping type, disposed at intervals in the lateral direction within the drift region; and a transition layer of the first doping type, connected under the pillar region. The thickness of the transition layer is larger than 2 microns and less than or equal to 11 microns, and the doping concentration of the transition layer ranges from larger than or equal to 2.4×1014/cm3 to less than or equal to 2.4×1016/cm3, in order to solve the technical problem of a large turn-off energy loss due to the tail current of the conventional SJ-IGBT device in the turn-off stage.