Super-junction Power MOSFET Resurf Region Design
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Solution Overview
Problem
In semiconductor power devices with super-junction structures, achieving a high breakdown voltage with low ON-resistance is challenging due to electric field concentration at the outer peripheral corners, which makes charge unbalance sensitive, especially in the trench fill method where process and design flexibility are limited.
Innovation Solution
A semiconductor device design where a surface resurf region of a second conductivity type is integrated between the main junction and the super-junction structure in the peripheral region, shifting the electric field concentration away from the super-junction structure, and floating field plates are used to further reduce electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a super-junction structure is introduced into the drift region to achieve high breakdown voltage and low ON-resistance, then the breakdown voltage and ON-resistance performance is improved, but electric field concentration occurs at the outer peripheral corners making the device sensitive to charge unbalance
Solution Approach 1:
A surface resurf region of second conductivity type is introduced as an intermediary structure between the main junction and the super-junction structure in the peripheral region. This resurf region acts as a mediator that redistributes the electric field, preventing concentration at the outer peripheral corners of the super-junction structure while maintaining the beneficial low ON-resistance and high breakdown voltage characteristics.
Solution Approach 2:
The patent applies different structural configurations to different regions of the device. The central active region maintains the super-junction structure for optimal performance, while the peripheral region incorporates the surface resurf region to specifically address electric field concentration issues at the boundaries, creating local quality variations that solve the global problem.
2Ease of manufacture
If the trench fill method is used to form the super-junction structure with simple process steps, then manufacturing complexity is reduced, but process and design flexibility is limited
Solution Approach 1:
The patent modifies the trench fill process parameters and structural configurations to achieve both simplicity and flexibility. By adjusting trench depth, width, filling ratios, and the addition of the surface resurf region, the process can be adapted to different device requirements while maintaining relative simplicity compared to multi-epitaxial methods.
3Reliability
If floating field plates are added to reduce electric field concentration, then breakdown voltage stability is improved, but device complexity increases
Solution Approach 1:
The floating field plates are merged with the existing peripheral structure, combining the field plate function with the peripheral region architecture. This integration approach reduces the overall device complexity compared to adding completely separate structures, while still achieving the goal of reducing electric field concentration and improving breakdown voltage stability.
Data Source
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AI summary
In the present invention, in a semiconductor power device such as a power MOSFET having a super-junction structure in each of an active cell region and a chip peripheral region and having its upper main surface covered by a resin molded body, a ring region of the first conductivity type is provided at this surface and outside the main junction region of a second conductivity type. This ring region surrounds the active cell region along an inner end of a column circular super-junction region of the second conductivity type. In the power MOSFET comprising this super-junction structure the deterioration of the breakdown voltage charateristic due to interfacial charge is reduced.