Power MOSFET Field Plate Breakdown Voltage
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Solution Overview
Problem
Conventional power MOSFETs face limitations in achieving high breakdown voltages due to low doping concentrations in drift regions and inefficient isolation techniques, leading to suboptimal device performance.
Innovation Solution
The formation of N-type drift regions with specific doping concentrations and the introduction of a field plate structure, which includes a conductive field plate over a dielectric layer, helps to increase breakdown voltage and minimize gate-to-drain capacitance by creating a reduced surface field (RESURF) structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low doping concentration is used in drift regions to increase breakdown voltage, then breakdown voltage increases, but device performance deteriorates due to inefficient isolation and suboptimal characteristics
Solution Approach 1:
The patent applies local quality by creating drift regions with specific localized doping concentrations adjacent to the channel region, while maintaining different doping characteristics in other areas. The drift region is formed with a controlled doping concentration that is higher than conventional designs in the critical area near the channel, improving device performance while maintaining high breakdown voltage through the RESURF structure.
Solution Approach 2:
The patent changes the doping concentration parameter in the drift region to optimize both breakdown voltage and device performance. By adjusting the doping concentration to specific ranges and creating a graded doping profile, the invention achieves improved electron mobility and reduced on-resistance while maintaining the high breakdown voltage characteristic of low-doped drift regions.
2Ease of manufacture
If conventional STI isolation is used, then isolation is provided, but gate-to-drain capacitance increases and breakdown voltage is limited
Solution Approach 1:
The patent extracts the STI isolation structure from beneath the gate electrode, eliminating the conventional STI region that was causing increased gate-to-drain capacitance and limiting breakdown voltage. By removing the STI isolation in this critical area and replacing it with a drift region extending to the substrate, the invention reduces parasitic capacitance and enables higher breakdown voltages while maintaining proper isolation through the drift region structure.
3Reliability
If drift region extends underlying the gate electrode, then breakdown voltage increases, but gate-to-drain capacitance increases
Solution Approach 1:
The patent addresses the capacitance issue by changing the spatial arrangement in the vertical dimension. The drift region extends underlying the gate electrode but is separated from it by a dielectric layer, creating a vertical separation that reduces electric field coupling and gate-to-drain capacitance while still allowing the drift region to provide high breakdown voltage through its extended structure into the substrate.
4Ease of manufacture
If doping concentration is increased to improve device performance, then device performance improves, but breakdown voltage decreases
Solution Approach 1:
The patent applies local quality by creating spatially varying doping concentrations - higher doping in the drift region adjacent to the channel for improved device performance, and lower doping in other drift region areas for maintaining high breakdown voltage. This localized differentiation allows simultaneous optimization of both device performance and breakdown voltage characteristics.
Solution Approach 2:
The patent segments the drift region into zones with different doping concentrations, with a first drift region having higher doping adjacent to the channel and a second drift region having lower doping extending further into the substrate. This segmentation allows each zone to fulfill its specific function - the high-doped region improves carrier transport and device performance, while the low-doped region maintains high breakdown voltage.
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 proposed solution significantly enhances the breakdown voltage of power MOSFETs, with simulated results showing a breakdown voltage increase from 15 V to 30 V, while also reducing gate-to-drain capacitance and improving device performance by controlling the thermal budget and profile of N-type drift regions.
Implementation Method 1
The concentrations of the drift regions are low, so that the breakdown voltages of the power MOSFETs are increased
Implementation Method 2
the introduction of a field plate structure, which includes a conductive field plate over a dielectric layer, helps to increase breakdown voltage and minimize gate-to-drain capacitance by creating a reduced surface field (RESURF) structure
Data Source
AI summary
A power MOSFET includes a semiconductor region extending from a top surface of a semiconductor substrate into the semiconductor substrate, wherein the semiconductor region is of a first conductivity type. A gate dielectric and a gate electrode are disposed over the semiconductor region. A drift region of a second conductivity type opposite the first conductivity type extends from the top surface of the semiconductor substrate into the semiconductor substrate. A dielectric layer has a portion over and in contact with a top surface of the drift region. A conductive field plate is over the dielectric layer. A source region and a drain region are on opposite sides of the gate electrode. The drain region is in contact with the first drift region. A bottom metal layer is over the field plate.