MOS-Gated Diode Structure for Reverse Mode Loss Reduction
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Solution Overview
Problem
Existing semiconductor devices, such as MOSFETs, face inefficiencies due to high losses during reverse mode operation, primarily caused by the body diode's forward bias, which is exacerbated by the use of Schottky diodes as shunting devices, leading to reliability issues and design complexities.
Innovation Solution
The integration of a MOS-gated diode (MGD) structure within the semiconductor device, featuring a second field-effect structure with a higher capacitance per unit area than the first, allows for reduced voltage drop and increased efficiency by enabling unipolar current flow during reverse mode, thereby minimizing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a Schottky diode is used as a shunting device to minimize losses during reverse mode, then the forward voltage drop is reduced, but the device complexity increases due to different metal requirements and manufacturing complications
Solution Approach 1:
The patent combines the MOSFET and diode functions into a single integrated structure where the body diode of the MOSFET serves as the shunting device. This eliminates the need for a separate Schottky diode and its associated manufacturing complexity while maintaining the low forward voltage drop characteristic.
Solution Approach 2:
The MOSFET body diode is designed to perform dual functions: as the intrinsic body diode during normal operation and as the shunting device during reverse mode. This multi-functionality eliminates the need for additional components and simplifies the manufacturing process.
2Productivity
If a Schottky diode is integrated to reduce reverse mode losses, then efficiency is improved, but reliability deteriorates due to high leakage current and reverse power dissipation
Solution Approach 1:
The patent changes the operating parameters of the body diode by controlling the gate voltage to keep it negative during reverse mode, ensuring the diode remains reverse-biased and does not conduct. This eliminates the high leakage current and reverse power dissipation issues associated with Schottky diodes while maintaining low losses through the MOSFET's low on-resistance.
3Loss of energy
If a shunting device is added in parallel to the body diode to minimize reverse mode losses, then efficiency is improved, but device complexity increases due to additional contacts and supply lines
Solution Approach 1:
The patent merges the shunting function with the existing MOSFET body diode structure. By utilizing the body diode's inherent parallel path and controlling its bias state through gate voltage, the patent eliminates the need for additional shunting devices, contacts, and supply lines while achieving the same loss reduction.
4Loss of energy
If Schottky diodes are used as shunting devices, then forward voltage drop is reduced, but manufacturing precision requirements increase due to metal-semiconductor barrier formation
Solution Approach 1:
The patent extracts the complex metal-semiconductor barrier formation process from the design by eliminating the Schottky diode entirely. Instead, it uses the MOSFET's existing pn-junction body diode with standard semiconductor manufacturing processes, thereby maintaining low forward voltage drop without the stringent manufacturing precision requirements.
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 approach reduces the voltage drop across the semiconductor device during reverse mode, enhancing efficiency and reliability by utilizing a MOS-gated diode structure that promotes unipolar current flow, thus overcoming the limitations of traditional Schottky diodes.
Implementation Method 1
the resistance of the device can be controlled by the voltage applied to the gate electrode of the field-effect controlled device
Implementation Method 2
In a 'reversed mode' of the field-effect controlled device, the pn-body diode is forward biased. This results in a loss which is mainly determined by the product of current flow and voltage drop across the body diode
Implementation Method 3
enabling unipolar current flow during reverse mode, thereby minimizing losses
Data Source
AI summary
A semiconductor device having a semiconductor body, a source metallization arranged on a first surface of the semiconductor body and a trench including a first trench portion and a second trench portion and extending from the first surface into the semiconductor body is provided. The semiconductor body further includes a pn-junction formed between a first semiconductor region and a second semiconductor region. The first trench portion includes an insulated gate electrode which is connected to the source metallization, and the second trench portion includes a conductive plug which is connected to the source metallization and to the second semiconductor region.