RC-IGBT N-type Cathode Layer Snapback Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Snapback occurs in Reverse-Conducting IGBTs (RC-IGBTs) due to suppressed hole injection from the p-type collector layer into the n-type cathode layer, leading to increased saturation voltage and degraded IGBT characteristics.
Innovation Solution
The semiconductor device incorporates a structure with an N-type cathode layer formed along the collector electrode, extending along the cell arrangement direction, and trench electrodes connected to the emitter electrode, which reduces electron diffusion from the IGBT region to the cathode layer, thereby suppressing snapback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an n-type cathode layer is formed on the rear surface of the FWD and bonded to the collector layer of the IGBT, then the RC-IGBT can be formed as a single chip, but snapback occurs due to suppressed hole injection leading to increased saturation voltage
Solution Approach 1:
The patent applies local quality by creating a dedicated suppression region with different doping characteristics (higher impurity concentration) in specific areas where electron diffusion needs to be controlled, while maintaining the original cathode layer structure in other regions. This localized modification suppresses snapback without compromising the single-chip integration benefit
Solution Approach 2:
The patent introduces a suppression region as an intermediary structure between the cathode layer and the IGBT region. This intermediate layer with higher impurity concentration acts as a barrier to electron diffusion, preventing electrons from reaching the IGBT region and causing snapback, while allowing the device to maintain its integrated single-chip structure
2Device complexity
If electrons flow into the n-type cathode layer adjacent to the IGBT, then the RC-IGBT structure is maintained, but hole injection from the p-type collector layer is suppressed leading to degraded IGBT characteristics
Solution Approach 1:
The patent modifies local properties by creating a suppression region with higher impurity concentration in specific zones adjacent to the IGBT region. This localized change in material properties (higher doping concentration) creates an electron barrier that prevents electron diffusion into the IGBT region, thereby preserving hole injection characteristics and maintaining reliable IGBT operation while keeping the integrated structure
Solution Approach 2:
The patent introduces asymmetry by creating non-uniform doping distribution across the cathode layer structure. The suppression region has higher impurity concentration compared to other cathode layer regions, creating an asymmetric electron barrier that selectively blocks electron diffusion paths toward the IGBT region while maintaining the integrated device structure
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 reverse recovery current and loss by minimizing electron flow into the cathode layer, maintaining breakdown voltage and improving switching characteristics.
Implementation Method 1
reduces electron diffusion from the IGBT region to the cathode layer
Implementation Method 2
trench electrodes connected to the emitter electrode, which reduces electron diffusion from the IGBT region to the cathode layer
Data Source
Figure 1
Figure 2
Figure 3
AI summary
According to one embodiment, a semiconductor device 100 includes a semiconductor substrate 1 including a first principal surface and a second principal surface, an emitter electrode 46, a gate wiring 49, a collector electrode 43, a first unit cell region 10 that is extended along one direction in a plane parallel to the first principal surface, and a second unit cell region 20 that is extended along one direction, in which the semiconductor substrate 1 of the first unit cell region 10 and the second unit cell region 20 includes an N- type drift layer 39, an N type hole barrier layer 38, a trench electrode 13, a P type body layer 36, an insulating film 35, an N type field stop layer 41, and a P+ type collector layer 42, and the second unit cell region 20 includes an N type cathode layer 47 that is fitted into the collector layer 42 and is extended along one direction.