LDMOS Body Structure to Prevent Reverse Recovery Failure
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Solution Overview
Problem
In laterally diffused metal oxide semiconductor (LDMOS) devices, reverse recovery failure occurs due to voltage drops between the body and source regions, leading to parasitic NPN activation and current spikes, compromising device reliability and safety.
Innovation Solution
The device incorporates a second body region and a conductivity type region to isolate the source region, preventing electron implantation and avoiding parasitic NPN activation during reverse recovery, thus preventing reverse recovery failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDMOS device structure is used, then the device achieves basic conduction capability, but reverse recovery failure occurs due to parasitic NPN activation caused by voltage drops in the P-body region
Solution Approach 1:
The P-body region is segmented into multiple P-body regions (first P-body region, second P-body region, third P-body region) with different doping concentrations. This segmentation allows each region to have optimized electrical characteristics, reducing overall resistance and preventing parasitic NPN activation during reverse recovery, thereby improving reliability without excessive structural complexity
Solution Approach 2:
Different regions of the P-body are assigned different doping concentrations to achieve local optimization. The first P-body region has higher doping concentration to reduce resistance near the source, while other regions have lower concentrations to maintain breakdown voltage characteristics. This local quality differentiation resolves the contradiction by improving reverse recovery performance in critical areas without compromising overall device structure
2Reliability
If the P-body region resistance is reduced to prevent voltage drops, then reverse recovery performance improves, but the breakdown voltage capability deteriorates
Solution Approach 1:
The P-body region is divided into multiple zones with different doping concentrations. The first P-body region adjacent to the source has higher doping concentration to reduce resistance and voltage drops, improving reverse recovery performance. The second and third P-body regions have lower doping concentrations to maintain high breakdown voltage capability. This local differentiation resolves the contradiction between reverse recovery performance and breakdown voltage capability
Solution Approach 2:
The P-body is segmented into multiple regions with graded doping concentrations, creating a transition from high-doping near the source to low-doping toward the drain. This segmentation allows the device to achieve low resistance in critical current paths while maintaining high breakdown voltage in the drift region, resolving the contradiction between reverse recovery performance and voltage blocking capability
Data Source
AI summary
A laterally double-diffused metal oxide semiconductor device is provided, including: a drift region (3) having a first conductivity type; a first body region (10) disposed on the drift region (3) and having a second conductivity type, the first conductivity type and the second conductivity type being opposite conductivity types; a first conductivity type region (13) disposed in the first body region (10); a second body region (12) disposed in the first conductivity type region (13) and having the second conductivity type; a source region (11) disposed in the second body region (12) and having the first conductivity type; and a contact region (9) disposed in the first body region (10) and having the second conductivity type.