Power MOSFET Superjunction Column Width Optimization
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Solution Overview
Problem
Conventional techniques for developing high-breakdown voltage power MOSFETs with low on-resistance, such as multi-epitaxy and epitaxy trench filling methods, face challenges due to electric field concentration at the intermediate region between the active cell and chip peripheral areas, leading to reduced source-drain breakdown voltage.
Innovation Solution
A power semiconductor device with a superjunction structure in the drift regions of the active cell, chip peripheral region, and intermediate region, where the width of column regions of a second conductivity type is made larger in the intermediate region to shift the peak electric field depth from the surface to the inner part of the drift region, thereby addressing local charge unbalance and electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional multi-epitaxy or epitaxy trench filling methods are used to create superjunction structure, then breakdown voltage can be enhanced, but electric field concentration occurs at the intermediate region between active cell and chip peripheral areas, reducing source-drain breakdown voltage
Solution Approach 1:
The patent applies local quality by making the width of column regions of the second conductivity type larger specifically in the intermediate region between the active cell region and chip peripheral region, while maintaining standard dimensions in other areas. This localized dimensional change addresses the electric field concentration problem specifically where it occurs without affecting the overall device performance
Solution Approach 2:
The patent changes the width parameter of column regions in the intermediate region to be larger than in other regions. This parameter modification shifts the peak electric field depth from the surface to the inner part of the drift region, thereby reducing electric field concentration and enhancing source-drain breakdown voltage
2Reliability
If the width of column regions is increased in the intermediate region, then electric field peak depth shifts to inner part of drift region, but device structure becomes more complex
Solution Approach 1:
The patent implements local quality by applying the width modification only to column regions in the intermediate region, leaving other regions with standard dimensions. This localized approach reduces the overall structural complexity compared to modifying the entire device, while still achieving the desired electric field distribution improvement
Data Source
AI summary
A problem associated with n-channel power MOSFETs and the like that the following is caused even by relatively slight fluctuation in various process parameters is solved: source-drain breakdown voltage is reduced by breakdown at an end of a p-type body region in proximity to a portion in the vicinity of an annular intermediate region between an active cell region and a chip peripheral portion, arising from electric field concentration in that area. To solve this problem, the following measure is taken in a power semiconductor device having a superjunction structure in the respective drift regions of a first conductivity type of an active cell region, a chip peripheral region, and an intermediate region located therebetween: the width of at least one of column regions of a second conductivity type comprising the superjunction structure in the intermediate region is made larger than the width of the other regions.