Monolithic MOSFET Rectifier With Tunable Forward Voltage Drop
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Solution Overview
Problem
Existing power MOSFET devices have a high forward voltage drop of the body diode, which limits switching speed and efficiency in switching circuit applications.
Innovation Solution
A monolithic integrated circuit power MOSFET device with an embedded rectifying diode, where the forward voltage drop of the rectifying diode is process tunable to improve switching speed and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a body diode is used in power MOSFET, then rectification function is provided, but forward voltage drop is too high which limits switching speed and efficiency
Solution Approach 1:
The patent merges the rectifier diode and MOSFET into a single monolithic integrated structure on the same semiconductor substrate. The rectifier diode is formed by implanting first and second dopants to create a p-n junction, while the MOSFET is formed in the same substrate with shared regions. This integration allows the rectifier diode to provide low forward voltage drop (improving energy loss) while the MOSFET provides fast switching capability, resolving the contradiction between low voltage drop and high switching speed.
2Reliability
If body diode is used for rectification, then diode function is achieved, but switching speed and efficiency are limited due to high forward voltage drop
Solution Approach 1:
The patent combines the rectifier diode and MOSFET functions in a single integrated device. The rectifier diode ensures reliable rectification through its p-n junction structure, while the integrated MOSFET provides efficient switching control. The shared semiconductor substrate and interconnected regions enable both functions to operate optimally together, achieving both reliability in rectification and high switching efficiency simultaneously.
3Device complexity
If standard body diode structure is used, then simple structure is maintained, but forward voltage drop cannot be reduced for faster switching
Solution Approach 1:
The patent integrates the rectifier diode and MOSFET structures on the same substrate with shared regions, creating a compact design that does not significantly increase device complexity. The rectifier diode is formed using dopant implantation in the same substrate where the MOSFET is fabricated, allowing both structures to share common regions and minimally increasing manufacturing steps. This integration achieves low forward voltage drop without substantial increase in structural complexity.
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 integration of a process-tunable rectifying diode within the power MOSFET device reduces the forward voltage drop, enhancing switching speed and efficiency while supporting a wide range of applications.
Implementation Method 1
An additional rectifying diode D2 is electrically coupled in parallel with body diode D1 between the body B (source S) and drain D
Data Source
Figure 1~3B
Figure 3C~4B
Figure 4C~5
AI summary
An integrated circuit includes a MOSFET device and a monolithic diode device, wherein the monolithic diode device is electrically connected in parallel with a body diode of the MOSFET device. The monolithic diode device is configured so that a forward voltage drop VfD2 of the monolithic diode device is less than a forward voltage drop VfD1 of the body diode of the MOSFET device. The forward voltage drop VfD2 is process tunable by controlling a gate oxide thickness, a channel length and body doping concentration level. The tunability of the forward voltage drop VfD2 advantageously permits design of the integrated circuit to suit a wide range of applications according to requirements of switching speed and efficiency.