Superjunction MOSFET Corner Layout for Charge Balance
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Solution Overview
Problem
Superjunction MOSFET devices face challenges in maintaining charge balance at corner and termination regions, leading to reduced breakdown voltage and device robustness due to difficulties in achieving uniform electric field distribution.
Innovation Solution
A two-dimensional approach is used to optimize the layout of active cell and termination column structures by adjusting the dose and distribution of dopants, incorporating curvature considerations and forming edge rings to balance charges, ensuring that the ratio of P-type to N-type doped areas maintains charge balance in corner regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If P columns are arranged in uniform parallel rows in the central active region, then manufacturing simplicity is improved, but charge balance at corner and termination regions deteriorates
Solution Approach 1:
The patent applies different P column layout configurations to different regions: uniform parallel rows in the central active region for manufacturing simplicity, and curved/adjusted patterns at corner and termination regions for charge balance. This local differentiation resolves the contradiction by optimizing each region according to its specific requirements.
Solution Approach 2:
The device is divided into distinct regions (central active region vs. corner/termination regions) with different P column arrangements. The central region uses simple uniform rows while corner regions use specialized curved patterns, allowing each segment to be optimized independently for its function.
2Reliability
If curved termination design is used in corner region, then breakdown voltage is improved by reducing E-field, but P column layout matching for charge balance becomes more challenging
Solution Approach 1:
The patent employs curved P column patterns at corner regions instead of straight lines. The curved geometry follows the circular field plate contours and reduces electric field concentration at sharp corners, thereby improving breakdown voltage while maintaining charge balance through careful curvature radius selection.
3Reliability
If charge balance is achieved in corner regions, then breakdown voltage uniformity is improved, but device complexity increases due to optimized corner and termination region design
Solution Approach 1:
The patent designs the P column layouts in corner and termination regions to achieve equipotential distribution and uniform electric field characteristics. By carefully positioning P columns to balance charges, the design ensures uniform breakdown voltage across the entire device surface, including corners and termination regions.
Data Source
AI summary
A superjunction device and methods for layout design and fabrication of a superjunction device are disclosed. A layout of active cell column structures can be configured so that a charge due to first conductivity type dopants balances out charge due to second conductivity type dopants in a doped layer in an active cell region. A layout of end portions of the active cell column structures proximate termination column structures can be configured so that a charge due to the first conductivity type dopants in the end portions and a charge due to the first conductivity type dopants in the termination column structures balances out charge due to the second conductivity type dopants in a portion of the doped layer between the termination column structures and the end portions.