MOSFET with MOS-Gated Diode Reducing Reverse Voltage Drop
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Solution Overview
Problem
Existing power semiconductor devices, such as MOSFETs, face inefficiencies due to high losses during reverse mode operation, primarily caused by the body diode's forward voltage drop, which is not effectively mitigated by conventional Schottky diodes due to their manufacturing complexities and reliability issues.
Innovation Solution
The semiconductor device incorporates a second field-effect structure with a higher capacitance per unit area, specifically a MOS-gated diode (MGD), connected in parallel to the body diode, which reduces the voltage drop during reverse mode by facilitating unipolar current flow through an inversion channel, thereby minimizing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a Schottky diode is used as an integrated shunting device, then the forward voltage drop is reduced, but the manufacturing complexity increases and reliability decreases
Solution Approach 1:
The patent changes the fundamental operating principle of the shunting device from Schottky diode (metal-semiconductor junction) to MOS-gated diode (field-effect controlled). This parameter change in the device physics enables low forward voltage drop through field-effect control while avoiding the manufacturing complexities of Schottky contacts, as the MOS structure uses standard semiconductor fabrication processes
Solution Approach 2:
The patent uses a MOS-gated diode structure that replicates the functional benefits of a Schottky diode (low forward voltage drop, fast switching) but implements it through a different physical mechanism (field-effect control versus metal-semiconductor barrier) that is more compatible with standard manufacturing processes
2Loss of energy
If a Schottky diode is used as an integrated shunting device, then the turn-on voltage is reduced, but reliability problems increase due to leakage current and reverse power dissipation
Solution Approach 1:
The patent replaces the physical metal-semiconductor barrier mechanism of Schottky diodes with an electric field-controlled mechanism in MOS-gated diodes. This substitution allows precise control of the shunting path through gate voltage, eliminating the uncontrolled leakage currents and reverse power dissipation issues inherent in Schottky structures
Solution Approach 2:
The patent changes the control mechanism from passive metal-semiconductor junction to active field-effect control, enabling dynamic adjustment of the shunting device characteristics through gate voltage to optimize reliability while maintaining low turn-on voltage
3Loss of energy
If a shunting device is added in parallel to the body diode, then losses during reverse mode are reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the shunting device functionality directly into the MOSFET structure by forming the MOS-gated diode using the same semiconductor substrate and fabrication processes, eliminating the need for separate Schottky diode integration and its associated manufacturing complexities
Solution Approach 2:
The patent creates a multi-functional device where the MOS-gated diode serves both as the primary switching element and as the shunting device, eliminating the need for separate components and simplifying the manufacturing process while maintaining the ability to reduce reverse mode losses
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
This configuration significantly reduces the voltage drop across the semiconductor device during reverse mode, enhancing the efficiency of power converters and reducing electric losses, compared to standard MOSFETs.
Implementation Method 1
A first capacitance is formed between the first gate electrode and the body region. The second field-effect structure further includes a second gate electrode which is connected to the source metallization and a second insulating region which is arranged at least between the second gate electrode and the body region. A second capacitance is formed between the second gate electrode and the body region. The capacitance per unit area of the second capacitance is larger than the capacitance per unit area of the first capacitance.
Data Source
AI summary
A semiconductor device includes a source metallization, a source region of a first conductivity type in contact with the source metallization, a body region of a second conductivity type which is adjacent to the source region. The semiconductor device further includes a first field-effect structure including a first insulated gate electrode and a second field-effect structure including a second insulated gate electrode which is electrically connected to the source metallization. The capacitance per unit area between the second insulated gate electrode and the body region is larger than the capacitance per unit area between the first insulated gate electrode and the body region.