Superjunction Termination Structure Uniform Epitaxial Filling
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Solution Overview
Problem
Conventional superjunction devices face challenges in forming P-type and N-type pillars and designing a proper termination structure due to varying epitaxial growth rates on different crystal orientations, leading to defects and voids in the silicon filling process, particularly in the corner portions of annular-shaped trenches.
Innovation Solution
A superjunction device with a termination structure featuring annular-shaped trenches where the Miller indices of all sidewalls and bottom faces belong to the {100} family of crystal planes, ensuring uniform epitaxial growth and filling of silicon, eliminating defects in the corner portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If annular-shaped trenches are used in the termination structure, then the breakdown voltage is improved, but the epitaxial filling quality deteriorates due to varying growth rates at different crystal orientations
Solution Approach 1:
The patent applies local quality by making the corner portions of the annular-shaped trenches have the same crystal orientation as the straight sides, specifically ensuring that both the sidewalls and bottom faces of the corner portions belong to the {100} family of crystal planes. This local optimization ensures uniform epitaxial growth rate throughout the entire trench structure, eliminating the varying growth rates that previously caused filling defects at the corners while maintaining the high breakdown voltage benefits of the annular-shaped termination structure
2Ease of manufacture
If conventional silicon epitaxial growth technology is used, then the process is simple, but the filling quality varies due to crystal orientation dependence of growth rate
Solution Approach 1:
The patent applies parameter changes by modifying the crystal orientation parameters of the trench corner portions. Specifically, it ensures that the sidewalls and bottom faces of the corner portions have Miller indices belonging to the {100} family of crystal planes, matching the orientation of the straight sides. This parameter adjustment makes the epitaxial growth rate uniform across the entire trench structure, allowing conventional silicon epitaxial growth technology to achieve high filling quality without requiring complex new processes
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 results in improved performance by ensuring uniform filling of the corner portions of the annular-shaped trenches, preventing voids and enhancing the overall performance of the superjunction device.
Implementation Method 1
a semiconductor epitaxial layer having a first conductivity type, the semiconductor epitaxial layer being formed on the semiconductor substrate
Implementation Method 2
the silicon epitaxial growth rate is related with the crystal orientation of the silicon surface, and epitaxial growth rate varies
Data Source
AI summary
A superjunction device in which corner portions of each annular-shaped second trench are composed of a plurality of alternately arranged first sides and second sides. The first sides are parallel to a plurality of parallel arranged first trenches in a current-flowing area, while the second sides are perpendicular to the first sides and the first trenches. Such design ensures that Miller indices of sidewalls and bottom face of any portion of each second trench belong to the same family of crystal planes. Moreover, with this design, the corner portions of the second trenches can be filled with a silicon epitaxial material at the same rate with the rest portions thereof, which ensures for the second trenches to be uniformly and completely filled without any defects in the corner portions and hence improve the performance of the superjunction device.