Trench Edge Termination Superjunction MOSFET
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Solution Overview
Problem
Conventional edge termination structures for superjunction MOSFETs fail to maintain required breakdown voltages due to the complexity introduced by more heavily doped epitaxial layers, necessitating new termination structures and manufacturing methods that simplify the process while sustaining high breakdown voltages.
Innovation Solution
A semiconductor device with a field termination structure combined with a superjunction structure, featuring termination trenches and doped regions that compensate the epitaxial layer, reducing leakage and on-resistance, and enhancing breakdown voltage by allowing depletion region spread through trench fill materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional termination structures (floating rings and field plates) are used with heavily doped epitaxial layers in superjunction devices, then the manufacturing process remains simple, but the breakdown voltage requirement cannot be maintained
Solution Approach 1:
The termination region is segmented into multiple alternating p-type and n-type columns similar to the active region, creating a superjunction termination structure. This segmentation allows the termination region to maintain high breakdown voltage while being compatible with the heavily doped epitaxial layer, resolving the contradiction between reliability and manufacturing simplicity.
Solution Approach 2:
The patent applies different doping characteristics locally: the active region uses heavily doped epitaxial layers with alternating p-n columns for low on-resistance, while the termination region uses a superjunction structure with alternating p-n columns to maintain high breakdown voltage. This local quality differentiation resolves the contradiction by optimizing each region for its specific function.
2Reliability
If more heavily doped epitaxial layers are used in superjunction structures to reduce on-resistance, then Rdson decreases, but edge termination structures become more complicated
Solution Approach 1:
The patent merges the superjunction structure from the active region with the termination region, creating a unified superjunction device where both regions use alternating p-n columns. This merging eliminates the need for separate conventional termination structures, reducing device complexity while maintaining low on-resistance through the heavily doped epitaxial layer.
Solution Approach 2:
The superjunction structure with alternating p-n columns serves multiple functions: in the active region, it provides low on-resistance through n-type conduction paths, and in the termination region, it maintains high breakdown voltage through charge compensation. This universality resolves the contradiction by making the same structural approach effective for both low on-resistance and simplified termination.
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
The proposed solution effectively reduces electric field buildup and maintains high breakdown voltage, simplifying the manufacturing process and improving the performance of superjunction devices by integrating termination structures with active cell structures.
Implementation Method 1
doped regions that compensate the epitaxial layer, reducing leakage and on-resistance
Implementation Method 2
enhancing breakdown voltage by allowing depletion region spread through trench fill materials
Data Source
AI summary
In one embodiment, a device is formed in a region of semiconductor material. The device includes active cell trenches and termination trenches each having doped sidewall surfaces that compensate the region of semiconductor material during reverse bias conditions to form a superjunction structure. The termination trenches include a trench fill material that enhances depletion region spread during reverse bias conditions.