Super-Junction Edge Termination Using Floating Regions
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Solution Overview
Problem
Wide band gap power devices, such as silicon carbide (SiC) power devices, face challenges in maximizing the active area to overhead area ratio due to large termination areas, which limits efficiency and performance.
Innovation Solution
The design involves a super-junction (SJ) device with minimized epitaxial doping concentrations in termination areas and the use of floating regions to form a junction termination, allowing for a reduction in termination width and die area usage while maintaining high breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wide termination is used to prevent electric field crowding and improve device reliability, then breakdown voltage is maintained, but the termination area increases and the active area to overhead area ratio decreases
Solution Approach 1:
The patent applies different doping concentrations locally within the termination region. Specifically, it uses a first doping concentration in a first portion of the termination region and a second doping concentration in a second portion, where the ratio between them is optimized. This local differentiation allows the termination to maintain breakdown voltage while reducing the overall termination area, thereby improving the active area to overhead area ratio.
Solution Approach 2:
The patent changes the doping concentration parameter across different regions of the termination. By establishing a specific ratio between the first doping concentration and the second doping concentration, the patent optimizes the electric field distribution to maintain breakdown voltage while minimizing the termination area required.
2Reliability
If a wide termination is used to shape and control the electric field, then breakdown voltage is maintained, but the overhead area increases and die area available for active area decreases
Solution Approach 1:
The patent implements local quality by dividing the termination region into portions with different doping concentrations. This allows precise control over the electric field in different areas, enabling the termination to maintain breakdown voltage while occupying less area, thus increasing the active area to overhead area ratio.
Solution Approach 2:
By varying the doping concentration parameter across the termination region and optimizing the ratio between different doping concentrations, the patent achieves efficient electric field control with reduced termination area, thereby improving productivity in terms of active area utilization.
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 approach increases the active area to overhead area ratio, enhancing device efficiency and performance without compromising breakdown voltage, and is cost-effective to fabricate using common semiconductor fabrication equipment.
Implementation Method 1
a junction termination can be used to generally prevent electric field crowding near the edges of an active area of the device during reverse bias operation
Implementation Method 2
the termination area of the first and second epi layers has a minimized epi doping concentration of the first conductivity type
Data Source
AI summary
A disclosed super-junction (SJ) device includes a first epitaxial (epi) layer that forms a first SJ layer of the SJ device, and includes a second epi layer disposed on the first SJ layer that forms a device layer of the SJ device. An active area of the first and second epi layers includes a first set of SJ pillars comprising a particular doping concentration of a first conductivity type and a second set of SJ pillars comprising the particular doping concentration of a second conductivity type. A termination area of the first and second epi layers has a minimized epi doping concentration of the first conductivity type that is less than the particular doping concentration, and the termination area of the second epi layer includes a plurality of floating regions of the second conductivity type that form a junction termination of the SJ device.