ACCUFET Schottky Source Contact for Power Loss Reduction
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Solution Overview
Problem
Power MOSFETs with body diodes exhibit high resistance and power dissipation during reverse voltage conditions, which is undesirable, and existing solutions like copackaging with discrete Schottky diodes or forming a monolithic device require modifying the drift region for Schottky characteristics, potentially increasing overall resistance.
Innovation Solution
A monolithic, integrated power semiconductor device that includes an ACCUFET and a Schottky diode formed in a single die, where the source contact of the ACCUFET makes a Schottky contact with the base region, allowing the drift region to be made more conductive without altering its characteristics, and source field electrodes are used to deplete the drift region, enhancing breakdown voltage capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drift region is modified to form a Schottky diode with the source contact, then a Schottky diode function is achieved, but the overall resistance of the device increases
Solution Approach 1:
The device is segmented into two functional regions: the drift region maintains its original highly conductive characteristics for low resistance, while the base region is specifically configured to form the Schottky diode junction with the source contact. This segmentation allows each region to be optimized independently for its specific function without compromising the other.
Solution Approach 2:
Different regions of the device are given different electrical characteristics tailored to their specific functions. The drift region is designed for high conductivity to minimize resistance, while the base region is designed with specific properties to enable Schottky diode formation. This local differentiation resolves the contradiction by allowing the Schottky function to exist locally without increasing overall device resistance.
2Loss of energy
If the drift region is made more conductive, then power loss is reduced, but the breakdown voltage capability is compromised
Solution Approach 1:
The device separates the functions of conduction and voltage blocking into different regions. The drift region is optimized for high conductivity to reduce power loss during normal operation, while the base region provides the voltage blocking capability through Schottky diode formation. This segmentation allows both low resistance and high breakdown voltage to be achieved simultaneously in different parts of the device.
Solution Approach 2:
Different regions have different electrical properties optimized for their specific roles. The drift region has high conductivity for efficient current flow, while the base region has properties that enable high-voltage blocking through Schottky junction formation. This local quality differentiation resolves the contradiction between low power loss and high breakdown voltage capability.
3Loss of energy
If a discrete Schottky diode is copackaged with a power MOSFET, then power loss during reverse voltage is reduced, but device complexity increases
Solution Approach 1:
The Schottky diode function is merged with the existing power semiconductor device structure. The source contact, which already exists in the power MOSFET or ACCUFET, is configured to form a Schottky junction with the base region. This integration eliminates the need for separate discrete components and reduces device complexity while maintaining the power loss reduction benefit.
Solution Approach 2:
The source contact serves multiple functions: it acts as the source terminal for the power MOSFET/ACCUFET operation and simultaneously forms the Schottky diode anode. This multi-functionality reduces the number of required components and simplifies the overall device structure while achieving both power switching and reverse voltage protection functions.
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 allows for a more conductive drift region without compromising breakdown voltage, reducing power loss during reverse voltage conditions by eliminating the need to modify the drift region for Schottky characteristics, thus improving the efficiency of the power semiconductor device.
Implementation Method 1
the source contact of the ACCUFET makes a Schottky contact with the base region to form a Schottky diode
Implementation Method 2
source field electrodes which function to deplete the drift region
Data Source
AI summary
An accumulation mode FET (ACCUFET) which includes an insulated gate, an adjacently disposed insulated source field electrode, and a source contact that makes Schottky contact with the base region of the ACCUFET.