Wider Termination Mesa in Semiconductor Device for Avalanche Control
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Solution Overview
Problem
Power semiconductor devices face challenges in minimizing ohmic losses and maintaining non-problematic avalanche characteristics, particularly in achieving balanced dopant concentrations across the semiconductor mesas and termination structures without adverse effects on blocking capabilities.
Innovation Solution
The semiconductor device incorporates a termination mesa wider than the cell mesas, surrounded by a termination structure with the same thickness dielectric as the field dielectric, allowing for controlled dopant distribution and avalanche breakdown primarily in the cell field, reducing the risk of localized damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the termination mesa is made wider than the cell mesas, then the dopant concentration distribution is improved and avalanche characteristics are enhanced, but the device area increases
Solution Approach 1:
The patent applies local quality by creating a termination mesa with a different width than the cell mesas. The termination mesa is specifically designed to be wider to accommodate different dopant concentration requirements. This local structural differentiation allows the termination region to have optimized dopant distribution for reliable avalanche breakdown while the cell region maintains its functional characteristics, thus improving overall device reliability without unnecessarily increasing the entire device area.
Solution Approach 2:
The patent segments the semiconductor device into distinct regions with different mesa widths - the termination mesa is separated and made wider than the cell mesas. This segmentation allows independent optimization of each region: the wider termination mesa provides better dopant concentration distribution and avalanche characteristics, while the cell mesas maintain their compact size for functional efficiency, thereby resolving the contradiction between reliability improvement and area minimization.
2Loss of energy
If higher dopant concentrations are used in the semiconductor mesas, then the on state resistance is reduced, but the blocking capabilities are adversely impacted
Solution Approach 1:
The patent applies local quality by implementing different dopant concentrations in different regions. The termination mesa, being wider, can accommodate higher dopant concentrations without compromising blocking capabilities because the increased width provides sufficient depletion region volume. Meanwhile, the cell mesas maintain lower dopant concentrations optimized for their switching function. This spatial differentiation of dopant concentrations allows each region to be optimized for its specific function, reducing overall on-state resistance while maintaining blocking capability.
Solution Approach 2:
The patent changes the dopant concentration parameter differently across various regions of the device. By adjusting the dopant concentration in the termination mesa to be higher than in the cell mesas, the patent optimizes the electrical characteristics of each region. The higher dopant concentration in the termination region reduces on-state resistance in that area, while the overall device blocking capability is maintained through the combined effect of all regions with their respective optimized parameters.
3Reliability
If the termination structure is designed to deplete the same dopant concentration as the central portion, then the blocking capability is maintained, but the avalanche breakdown may occur in the termination region causing localized damage
Solution Approach 1:
The patent applies local quality by creating a wider termination mesa that can accommodate different dopant concentration profiles compared to the central cell region. This wider structure allows the termination mesa to distribute the avalanche breakdown energy over a larger volume, preventing localized damage. The termination mesa maintains sufficient blocking capability through its increased width rather than relying solely on dopant concentration matching, thus resolving the contradiction between maintaining blocking capability and preventing localized damage.
Solution Approach 2:
The patent segments the device into distinct functional regions with different structural characteristics. The termination mesa is segmented as a separate, wider structure from the cell mesas, allowing it to handle avalanche breakdown events differently. This segmentation enables the termination region to serve as a dedicated protection zone that can absorb and distribute avalanche energy, preventing it from concentrating in the cell region where it could cause localized damage, while still maintaining the required blocking capability.
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
This design effectively reduces ohmic losses and ensures reliable recovery from avalanche breakdown by distributing the breakdown voltage across a larger semiconductor volume, minimizing the risk of device damage.
Implementation Method 1
By thermal oxidation a field oxide layer is formed that equably lines the field electrode and termination trenches
Implementation Method 2
stripe-shaped compensation structures extending from the front side into the semiconductor die deplete semiconductor mesas formed between the stripe-shaped compensation structures
Implementation Method 3
ensures reliable recovery from avalanche breakdown by distributing the breakdown voltage across a larger semiconductor volume
Data Source
AI summary
A semiconductor device includes a cell field with a plurality of field electrode structures and cell mesas. The field electrode structures are arranged in lines. The cell mesas separate neighboring ones of the field electrode structures from each other. Each field electrode structure includes a field electrode and a field dielectric separating the field electrode from a semiconductor body. A termination structure surrounds the cell field, extends from a first surface into the semiconductor body, and includes a termination electrode and a termination dielectric separating the termination electrode from the semiconductor body. The termination and field dielectrics have the same thickness. A termination mesa, which is wider than the cell mesas, separates the termination structure from the cell field.