Superjunction MOSFET Schottky Integration for Ringing Suppression
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Solution Overview
Problem
Conventional power MOSFET devices face a tradeoff between on-resistance (Rds-on) and breakdown voltage (BV), with superjunction structures improving high voltage applications but failing in low voltage scenarios due to potential device failure from high voltage and current during hot swap, and fast switching causing switch-node ringing with voltage spikes.
Innovation Solution
Integration of Schottky diodes with superjunction power MOSFETs, forming Schottky contacts along sidewalls of trenches or on the surface of lightly doped semiconductor layers, reducing body diode forward voltage drop and minimizing stored charge for efficient operation in low, medium, and high voltage applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If superjunction structures are used in high voltage power MOSFET devices, then breakdown voltage is improved and on-resistance is reduced, but the device fails in low voltage applications due to high voltage spikes and high electric fields causing device failure
Solution Approach 1:
A Schottky diode is introduced as an intermediary component between the drain and source of the power MOSFET. The Schottky diode's low forward voltage drop and fast reverse recovery characteristics help suppress voltage spikes and reduce electric field stress during switching transitions, protecting the superjunction structure from breakdown in low voltage applications
Solution Approach 2:
The patent modifies the electrical parameters of the power MOSFET by integrating a Schottky diode with specific forward voltage drop characteristics. This changes the overall voltage-current relationship of the device, enabling it to operate reliably in low voltage applications by limiting peak voltages and reducing electric field intensity during switching events
2Loss of energy
If Schottky diodes are integrated into power MOSFET devices, then body diode forward voltage drop is reduced and stored charge is minimized, but device complexity increases
Solution Approach 1:
The Schottky diode is merged with the power MOSFET structure by forming the Schottky contact within the same device architecture. The Schottky contact is integrated into the drift region, sharing common structural elements such as the semiconductor substrate and doping regions, thereby reducing the need for separate discrete components
Solution Approach 2:
The integrated Schottky diode serves multiple functions: it provides a low forward voltage drop path for reverse current, minimizes stored charge during switching, and suppresses voltage spikes. This multi-functionality is achieved within a single device structure, reducing the need for additional external components
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 Schottky diodes enhance the efficiency of MOSFET devices by reducing body diode forward voltage drop and quickening reverse recovery time, minimizing switch-node ringing and device failure risks.
Implementation Method 1
Schottky contact is formed along the sidewalls of trenches or on the surface between p columns
Data Source
AI summary
A trench metal-oxide-semiconductor field-effect transistor (MOSFET) device comprises an active cell area including a plurality of superjunction trench power MOSFETs formed in an epitaxial layer. Each MOSFET includes source and body regions and a contact trench formed between first and second gate trenches. A region of the epitaxial layer between the gate trenches extends to the top surface of the epitaxial layer. An insulated gate electrode is formed in each gate trench. At least a portion of the contact trench extends from a top surface of the epitaxial layer to a depth that is shallower than the bottom of the body region.