RC-IGBT Anode Ratio Optimization for Reverse Recovery Current
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Solution Overview
Problem
Existing reverse conducting semiconductor devices with integrated insulated gate bipolar transistors and diodes face issues such as decreased breakdown voltage, increased on-state resistance, and higher reverse recovery current due to concentrated electrical field intensity and inefficient hole injection, particularly in trench gate structures.
Innovation Solution
A semiconductor device design featuring trenches in a stripe form with gate insulating film and gate electrode, a second conductivity type base region and anode region selectively provided in mesa portions, and a first conductivity type emitter region, with a specific anode ratio and depletion layer linkage to reduce reverse recovery current and improve diode characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a trench gate structure is used to reduce on-state resistance, then current capability is improved, but electrical field concentration increases causing breakdown voltage to decrease
Solution Approach 1:
The patent applies local quality by creating different structural characteristics in different regions: the trench gate structure provides high current capability in active regions, while field stop regions without trenches provide electrical field distribution to maintain breakdown voltage. This regional differentiation allows simultaneous optimization of both current capability and breakdown voltage.
Solution Approach 2:
The patent segments the semiconductor device into distinct functional regions: trench gate regions for current conduction and field stop regions for electrical field management. This segmentation allows each region to be optimized for its specific function, resolving the contradiction between current capability and breakdown voltage.
2Device complexity
If the diode portion is provided over the whole IGBT portion to reduce device size, then integration is improved, but reverse recovery current increases due to concentrated electrical field
Solution Approach 1:
The patent segments the diode structure by providing it only in field stop regions rather than across the entire IGBT portion. This segmentation reduces the total diode area, thereby reducing reverse recovery current, while maintaining functional integration through the shared substrate and selective region placement.
Solution Approach 2:
The patent applies local quality by selectively placing the diode portion only in field stop regions where electrical field concentration occurs. This localized placement addresses the harmful effect of reverse recovery current in specific areas without compromising overall device integration.
3Productivity
If trenches are disposed at short pitch to improve current distribution, then productivity is improved, but electrical field intensity increases causing breakdown resistance to decrease
Solution Approach 1:
The patent segments the trench distribution by concentrating trenches in IGBT active regions for improved current distribution, while leaving field stop regions without trenches to maintain electrical field distribution and breakdown resistance. This selective segmentation resolves the contradiction between productivity and reliability.
Solution Approach 2:
The patent applies local quality by providing trenches at short pitch only in regions where current distribution is needed (IGBT portions), while maintaining larger spacing or no trenches in regions where electrical field management is critical (field stop portions). This localized structural differentiation simultaneously achieves both current distribution improvement and breakdown resistance maintenance.
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 design effectively reduces reverse recovery current and loss, enhancing diode characteristics by optimizing the anode ratio and depletion layer linkage, thereby improving the performance of reverse conducting semiconductor devices.
Implementation Method 1
decreased breakdown voltage, increased on-state resistance, and higher reverse recovery current due to concentrated electrical field intensity
Implementation Method 2
A second conductivity type anode region is selectively provided in a mesa portion between neighboring trenches of the second element region. A first conductivity type emitter region is selectively provided inside the base region.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An IGBT is disposed in an IGBT portion (21), and an FWD is disposed in an FWD portion (22). A p-type base region (5-1) and an n--type drift region (1) are alternately exposed in a trench (2) longitudinal direction in a substrate front surface in a mesa portion between neighboring trenches (2) in the IGBT portion (21). A p-type anode region (5-2) and the n--type drift region (1) are alternately exposed in the trench (2) longitudinal direction in the substrate front surface in a mesa portion in the FWD portion (22), and a repetitive structure is formed with a portion of the n--type drift region (1) sandwiched between p-type anode regions (5-2) and one p-type anode region (5-2) in contact with the portion as one unit region. The proportion occupied by the p-type anode region (5-2) in one unit region (an anode ratio) (α) is 50% to 100%. Therefore, the diode characteristics of an RC-IGBT wherein an IGBT and FWD are incorporated in the same semiconductor substrate can be improved.