LDMOS Device with Integrated PN Junction Diodes for Recirculating Current
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Solution Overview
Problem
MOSFET devices with intrinsic diodes are prone to damage from high and fast recirculating currents in inductive load applications, and existing solutions using external diodes increase component count, cost, and current leakage, while alternative methods require complex control logic adaptations.
Innovation Solution
Integration of additional PN-junction diodes within the MOSFET device structure, externally to the active area, forming diodes with specific doping concentrations to handle high and fast recirculating currents without additional components or complex control logic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external diodes are added in parallel to intrinsic diodes, then robustness to high and fast recirculating currents is improved, but device complexity and component count increase
Solution Approach 1:
The patent merges the function of external protection diodes with the intrinsic diode by integrating a PN junction directly into the MOSFET structure. The P-type region is formed in the n-type drift region, creating an integrated diode that combines the rectification function of the intrinsic diode with the high-current capability of a dedicated PN junction diode, eliminating the need for separate external diodes
Solution Approach 2:
The integrated PN junction serves multiple functions: it provides the rectification function during normal operation like the intrinsic diode, and simultaneously acts as a high-current protection diode during recirculating current events. This multi-functional design eliminates the need for separate protection components
2Reliability
If external diodes are added in parallel to intrinsic diodes, then robustness to high and fast recirculating currents is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines the protection diode function with the MOSFET structure itself, eliminating the need for separate external diodes and their associated mounting, wiring, and assembly processes. This integration reduces component count and simplifies manufacturing
Solution Approach 2:
The integrated PN junction provides both normal rectification function and high-current protection function, eliminating the need for separate protection components and reducing overall device cost
3Reliability
If external diodes are added in parallel to intrinsic diodes, then robustness to high and fast recirculating currents is improved, but current leakage increases
Solution Approach 1:
The patent creates a localized high-quality PN junction with optimized doping profiles specifically designed to handle high currents. The P-type region is formed with specific doping concentration in the n-type drift region, creating a localized area with superior current handling capability while maintaining low leakage characteristics
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 integrated diodes enhance the MOSFET device's robustness to sustain high and fast recirculating currents, eliminating the need for external diodes and simplifying control logic, thereby improving reliability and reducing costs.
Implementation Method 1
a first PN-junction and a second PN-junction integrated in the structural body externally to the active area
Data Source
AI summary
A structural body made of semiconductor material includes an active area housing a drain region, a body region and a source region within the body region. An electrical-isolation trench extends in the structural body to surround the active area. A first PN-junction and a second PN-junction are integrated in the structural body between the active area and the trench, respectively located on opposite sides of the active area. The first and the second PN-junctions form a first diode and a second diode, with each diode having a respective cathode electrically coupled to the drain region of the MOSFET device and a respective anode electrically coupled to the source region of the MOSFET device.