Reverse-Conducting LIGBT Collector Structure for Faster Reverse Recovery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing reverse conducting lateral insulated-gate bipolar transistors (LIGBTs) face challenges in high voltage or ultra-high voltage conditions during reverse breakdown, with limited snap-back effect suppression and slow turn-off rates during reverse recovery, due to the limitations of Zener diodes used in previous designs.
Innovation Solution
The design incorporates a reverse conducting lateral insulated-gate bipolar transistor with multiple N-well regions, a P-well region between them, and N+ and P+ contact regions electrically connected to a collector terminal, enhancing the collector structure to improve switching characteristics and eliminate the need for a parallel freewheeling diode, thereby reducing turn-off loss and increasing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zener diode is used in the reverse conducting LIGBT, then the snap-back effect is suppressed, but the turn-off rate during reverse recovery remains slow and the device is limited under high voltage conditions
Solution Approach 1:
The collector region is segmented into multiple N-well regions (first N-well region, second N-well region, etc.) arranged at intervals, with P-well regions between them. This segmentation creates multiple independent freewheeling current paths, allowing faster extraction of stored holes compared to a single Zener diode structure, thereby improving the turn-off rate during reverse recovery while maintaining snap-back suppression.
Solution Approach 2:
The invention merges the functions of the Zener diode (snap-back suppression) and the freewheeling diode into a single integrated collector structure with alternating N-well and P-well regions. This unified structure eliminates the need for separate parallel FWD devices and achieves both snap-back suppression and fast reverse recovery characteristics simultaneously.
2Ease of operation
If a parallel FWD is added to the LIGBT, then the freewheeling function is provided, but the chip area increases and the switching characteristics require high matching
Solution Approach 1:
The freewheeling function is merged into the LIGBT's own collector structure through the alternating N-well and P-well regions. The P-well regions with N+ contact regions serve as integrated freewheeling paths, eliminating the need for separate parallel FWD devices and reducing chip area while maintaining the freewheeling function.
Solution Approach 2:
The collector structure with alternating N-well and P-well regions serves multiple functions: it provides snap-back suppression during turn-on, enables freewheeling during turn-off, and accelerates reverse recovery. This multi-functional integrated structure replaces what would traditionally require separate dedicated components.
3Device complexity
If the collector structure uses a single N-well region, then the structure is simple, but the reverse recovery process is slow and turn-off loss is high
Solution Approach 1:
The single N-well collector structure is segmented into multiple N-well regions arranged at intervals with P-well regions between them. This segmentation creates multiple parallel current paths for hole extraction during reverse recovery, significantly reducing turn-off loss and accelerating the reverse recovery process while maintaining manageable structural complexity.
Data Source
AI summary
A reverse conducting lateral insulated-gate bipolar transistor includes a drift region formed on a substrate, a gate located on the drift region, an emitter region located on the drift region and close to one side of the gate, and a collector region located on the drift region and away from one side of the gate. Two or more N-well regions arranged at intervals are provided on the side of the drift region where the collector region is located. A P-well region is provided between the two or more N-well regions arranged at intervals; a P+ contact region is provided on the N-well region; an N+ contact region is provided on the P-well region; both the P+ contact region and the N+ contact region are conductively connected to a collector lead-out end.