SiC Trench Termination Structure for High Blocking Voltage
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Solution Overview
Problem
Trench type silicon carbide (SiC) semiconductor devices face inefficiencies in edge terminations due to epitaxial silicon depletion and the complexity of guard ring optimization, limiting breakdown voltage achievement.
Innovation Solution
A trench type termination structure that extends around the periphery of the device, featuring a linking mesa region, guard ring implant, and a floating trench design with a field plate, which coordinates epitaxial silicon depletion and simplifies fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If planar type terminations (field plate, guard ring, JTE) are used in trench type SiC devices, then the blocking capability is improved, but the depletion efficiency is reduced because epitaxial silicon depletion starts at the trench bottom making these planar terminations inefficient
Solution Approach 1:
The patent transitions from planar 2D terminations to a 3D trench-based termination structure. The termination trench extends vertically into the drift region, creating a three-dimensional depletion pattern that efficiently utilizes the epitaxial silicon depletion starting at the trench bottom. This dimensional change allows the termination to work synergistically with the trench geometry rather than opposing it.
Solution Approach 2:
The termination structure is nested within the trench geometry. The termination trench is formed within the drift region, and the depletion region is contained and guided within this trench structure. The guard ring implant is positioned at the trench bottom, nesting the termination functionality within the existing trench architecture.
2Ease of manufacture
If guard ring technique is used in SiC technology, then the termination structure is simplified, but the breakdown voltage achievement is limited to about 50% of ideal due to difficulty in optimizing ring spacing
Solution Approach 1:
The patent changes the spatial parameters of the guard ring structure by positioning it at the trench bottom rather than as a planar ring. The guard ring implant is formed at a specific depth within the trench, creating an optimized electric field distribution that achieves higher breakdown voltage. This parameter change in positioning transforms the guard ring from a limiting structure to an effective termination solution.
3Reliability
If JTE technique is used to provide good termination efficiency, then the depletion efficiency is improved, but the fabrication process complexity increases significantly compared to guard ring and field termination techniques
Solution Approach 1:
The patent merges the termination function with the existing trench structure. The termination trench is formed using the same trench fabrication process as the main device, and the guard ring implant is integrated into this structure. This merging eliminates the need for separate complex JTE fabrication steps while achieving comparable or superior termination efficiency.
Data Source
AI summary
A silicon carbide device has a termination region that includes a mesa region that links the termination region to an active area of the device and that includes one or more trenches.