3D Super Junction Power MOSFET Depletion Region Design
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Solution Overview
Problem
Power MOSFET devices with three-dimensional super junctions face limitations in breakdown voltage due to the horizontal diffusion of the depletion region, which restricts the width of the depletion region and subsequently the breakdown voltage, necessitating an enhancement to increase the breakdown voltage and reduce conduction resistance.
Innovation Solution
The implementation of a power MOSFET device with a three-dimensional super junction structure, featuring first and second trench wells with varying ion doping concentrations and widths, allowing for both horizontal and vertical depletion region formation between trench wells and the epitaxy layer, thereby increasing the depletion region and enhancing breakdown voltage, while reducing conduction resistance by increasing the width of the epitaxy layer between trench wells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the depletion region width is increased to increase breakdown voltage, then the breakdown voltage is improved, but the horizontal diffusion limits the depletion region width, causing the breakdown voltage to be limited
Solution Approach 1:
The patent transitions from a two-dimensional horizontal depletion region to a three-dimensional depletion region by introducing vertical trench structures. The depletion region extends both horizontally between trenches and vertically within the trench depth, effectively increasing the total depletion region volume and width without being constrained by horizontal diffusion alone. This dimensional transition allows the depletion region to achieve greater extent in both horizontal and vertical directions, thereby increasing breakdown voltage.
2Strength
If the depletion region width is increased to increase breakdown voltage, then the breakdown voltage is improved, but the device structure becomes more complex with multiple trench wells
Solution Approach 1:
The patent divides the depletion region formation into multiple segments: first trench wells that extend partially into the epitaxy layer, second trench wells that extend deeper, and the epitaxy layer itself. Each segment contributes differently to the overall depletion region, with first trench wells providing horizontal depletion and second trench wells providing vertical depletion. This segmentation allows the complex three-dimensional depletion region to be constructed from simpler, manageable components with different doping concentrations and depths.
3Strength
If the ion doping concentration of first trench well is decreased to increase depletion region, then the breakdown voltage is improved, but the conduction resistor increases when device is turned on
Solution Approach 1:
The patent applies different ion doping concentrations to different regions: the first trench wells have lower ion doping concentration to facilitate wider depletion region formation and higher breakdown voltage, while the second trench wells have higher ion doping concentration to maintain low conduction resistance when the device is turned on. This local quality differentiation allows each region to optimize for its specific function - the first trench wells for breakdown voltage and the second trench wells for conduction performance.
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 enhanced depletion region structure increases the breakdown voltage of the power MOSFET device and reduces conduction resistance when the device is turned on, improving its operational efficiency.
Implementation Method 1
the power MOSFET device utilizes a PN junction between a P-well and an N type epitaxy layer of the power MOSFET device to form a depletion region
Implementation Method 2
ion doping concentration of each first trench well of the plurality of first trench wells is less than ion doping concentration of a corresponding second trench well
Data Source
AI summary
A power metal-oxide-semiconductor field-effect transistor (MOSFET) device includes a first metal layer, a substrate, an epitaxy layer, a plurality of first trench wells, a plurality of second trench wells, a plurality of body structure layers, a plurality of polysilicon layers, and a second metal layer. A part of a depletion region is formed between each first trench well and the epitaxy layer and between a body structure layer corresponding to the each first trench well and the epitaxy layer, and a rest part of the depletion region is formed between a second trench well corresponding to the each first trench well and the epitaxy layer. The plurality of second trench wells increase a breakdown voltage of the power MOSFET device and reduce a conduction resistor of the power MOSFET device.