Asymmetric Super Junction MOSFET for Surge Voltage Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional MOSFETs used in power conversion circuits experience oscillation and increased surge voltage due to reverse recovery current when turned on, which affects their performance and reliability.
Innovation Solution
A MOSFET with a semiconductor base substrate featuring a super junction structure where the p-type column region has a higher dopant amount than the n-type column region, creating a low electric field region at the center of the n-type column region, minimizing electron movement and reducing oscillation and surge voltage when turned on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional MOSFET with balanced dopant amounts in n-type and p-type column regions is used, then the MOSFET achieves low ON resistance and high withstand voltage, but oscillation occurs and surge voltage increases when the MOSFET is turned on due to reverse recovery current
Solution Approach 1:
The patent applies local quality by creating a low electric field region specifically at the center of the n-type column region through asymmetric dopant distribution. The p-type column region has a higher dopant amount than the n-type column region, which locally modifies the electric field characteristics at the center portion to reduce reverse recovery current effects, thereby minimizing oscillation and surge voltage without compromising overall device performance
Solution Approach 2:
The patent changes the dopant amount parameter by setting the total dopant amount in the p-type column region to be higher than that in the n-type column region. This parameter change creates the desired low electric field region at the center of the n-type column region, fundamentally altering the electric field distribution to reduce reverse recovery current and its harmful effects
2Reliability
If the p-type column region has higher dopant amount than the n-type column region, then a low electric field region appears at the center of the n-type column region reducing oscillation and surge voltage, but the dopant balance is disrupted
Solution Approach 1:
The asymmetric dopant distribution creates local quality differences where the p-type column region has higher dopant concentration specifically tailored to generate a low electric field region at the center of the n-type column region. This localized modification achieves surge voltage reduction while the overall super junction structure maintains functional stability
Solution Approach 2:
The patent deliberately introduces asymmetry by setting different dopant amounts in the p-type and n-type column regions, with the p-type having higher dopant amount. This asymmetric design breaks the conventional balanced structure to create the low electric field region, accepting controlled compositional imbalance to achieve superior electrical 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 solution effectively minimizes oscillation in the MOSFET and decreases surge voltage, while also shortening turn-off time and reducing avalanche breakdown, maintaining low ON resistance and high withstand voltage.
Implementation Method 1
a low electric field region having lower field intensity than an area of the n-type column region other than the center of the n-type column region appears
Data Source
AI summary
A MOSFET used in a power conversion circuit including a reactor, a power source, the MOSFET, and a rectifier element, includes a semiconductor base substrate having an n-type column region and a p-type column region, the n-type column region and the p-type column region forming a super junction structure, the n-type column region and the p-type column region are formed such that a total amount of a dopant in the p-type column region is set higher than a total amount of a dopant in the n-type column region, and the MOSFET is configured to be operated in response to turning on of the MOSFET such that at a center of the n-type column region as viewed in a plan view, a low electric field region having lower field intensity than areas of the n-type column region other than the center of the n-type column region appears.