Super Junction MOSFET Pillar Doping for Breakdown Voltage
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Solution Overview
Problem
Existing super junction MOSFETs face challenges in improving the Figure of Merit (FOM) when reducing the cell pitch, as this often leads to a decrease in breakdown voltage due to increased electric fields.
Innovation Solution
The semiconductor power device incorporates a super junction region with specific doping concentration profiles for the first and second pillars, where the doping concentration of the first pillar is constant or increases from the drift region to the body region, and the doping concentration of the second pillar decreases from the drift region to the body region, thereby enhancing breakdown voltage and FOM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cell pitch is decreased to improve productivity, then the specific resistance decreases, but the breakdown voltage decreases due to increased electric field at the top portion of the super junction region
Solution Approach 1:
The patent applies local quality by creating different doping concentration profiles in different regions of the super junction. Specifically, the top portion (adjacent to drift region) has a lower doping concentration than the bottom portion (adjacent to body region), which locally optimizes the electric field distribution to prevent premature breakdown while maintaining low specific resistance overall.
Solution Approach 2:
The patent changes the doping concentration parameter along the vertical direction within the super junction region. By implementing a graded doping profile where concentration varies from top to bottom, the patent simultaneously achieves low specific resistance (through adequate doping) and high breakdown voltage (through reduced electric field at the top interface).
2Quantity of substance
If the doping concentration in the super junction region is increased to decrease specific resistance, then the specific resistance decreases, but the breakdown voltage decreases due to increased electric field
Solution Approach 1:
The patent applies local quality by creating different doping concentration profiles in different regions of the super junction. Specifically, the top portion (adjacent to drift region) has a lower doping concentration than the bottom portion (adjacent to body region), which locally optimizes the electric field distribution to prevent premature breakdown while maintaining low specific resistance overall.
Solution Approach 2:
The patent changes the doping concentration parameter along the vertical direction within the super junction region. By implementing a graded doping profile where concentration varies from top to bottom, the patent simultaneously achieves low specific resistance (through adequate doping) and high breakdown voltage (through reduced electric field at the top interface).
Data Source
AI summary
A semiconductor power device includes an active region that has a drift region of a first conductivity type and a body region of a second, opposite conductivity type. A super junction region is arranged at least partially between the drift region and the body region. The super junction region has a first pillar of the first conductivity type and at least a portion of a second pillar of the second conductivity type. The first pillar is arranged adjacent to the portion of the second pillar. At least one of: a doping concentration of the first pillar is constant and a doping concentration of the portion of the second pillar decreases, or the doping concentration of the first pillar increases and the doping concentration of the portion of the second pillar is constant.