Floating Field Ring Termination Design for Power Semiconductors
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Solution Overview
Problem
Current power semiconductor devices with floating field ring (FFR) terminations face challenges in achieving optimal safe operating area without increasing the wafer area, especially for high-voltage components, due to complex design requirements and limitations in silicon carbide process technology.
Innovation Solution
A power semiconductor device design featuring a two-zone linear ring-to-ring separation formula for floating field rings, where the separation increment changes significantly between zones, optimizing the safe operating area without increasing the wafer area occupied by the FFR termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a FFR termination is designed with constant ring-to-ring separation, then the manufacturing process is simple, but the safe operating area is not optimized
Solution Approach 1:
The termination region is segmented into two distinct zones with different ring-to-ring separation characteristics. The first zone has a smaller separation distance to concentrate field control near the active area, while the second zone has a larger separation to extend protection outward. This segmentation allows optimization of both safe operating area and manufacturing simplicity by addressing different functional requirements in different regions.
Solution Approach 2:
Different ring-to-ring separation distances are applied locally to different zones within the termination region. The first zone employs a smaller separation distance to effectively control electric field distribution near the active area, while the second zone uses a larger separation. This local differentiation optimizes the safe operating area without requiring complex manufacturing processes throughout the entire structure.
2Reliability
If the number of floating field rings is increased to achieve higher breakdown voltage, then the breakdown voltage increases, but the wafer area occupied by the FFR termination increases
Solution Approach 1:
The ring-to-ring separation distance is made dynamic rather than constant, with the first zone having a smaller separation and the second zone having a larger separation. This dynamic configuration allows the FFR termination to achieve higher breakdown voltages with fewer rings by concentrating the field control effect where it is most needed (near the active area), thereby reducing the total wafer area required compared to uniform separation designs.
3Reliability
If complex analytical methods are used to optimize FFR termination design, then the breakdown voltage is optimized, but the computational effort and design complexity increase
Solution Approach 1:
The design parameters are simplified by establishing a two-zone structure with defined separation characteristics rather than requiring complex continuous optimization. The first zone uses a smaller ring-to-ring separation and the second zone uses a larger separation, providing a practical parameter configuration that achieves good breakdown voltage performance without requiring complex analytical methods or high computational effort for design optimization.
Data Source
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AI summary
In a power semiconductor device (1) of the invention a total number n of floating field rings (10_1 to 10_n) formed in a termination area (TR) is at least 10. For any integer i in a range from i = 2 to i = n, a ring-to-ring separation di,i-1 between an i-th floating field ring and a directly adjacent (i-1)-th floating field ring, when counting the floating field rings (10_1 to 10_n) along a straight line starting from a main pn-junction (11) and extending in a lateral direction away from the main pn-junction (11), is given by the following formula: formula (I) for i = 2 to n, wherein d1,0 is a distance between the innermost floating field ring (10_1) closest to the main pn-junction (11) and the main pn-junction (11), and wherein: Δ zone1 − 0.05 ⋅ Δ zone2 < Δj < Δ zone1 + 0.05 ⋅ Δ zone2 for j = 1 to l-2, 2 ⋅ Δ zone2 <|Δj| < 10 ⋅ Δ zone2 ⋅ for j = l-1 0,95 ⋅ Δ zone2 < Δj < 1,05 ⋅ Δ zone2 for j = l to n-1, Δ zone2 > 0.1 μm, and −ΔΔ zone2 /2 < Δ zone1 <Δ zone2 /2, wherein I is an integer, for which 3 ≤ l ≤ n/2.