SiC Edge Termination Structure for Power Devices
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Solution Overview
Problem
Existing edge termination structures for power integrated devices, particularly those made in silicon carbide substrates, face challenges in achieving optimal breakdown voltage due to electric field peaks and manufacturing complexity, with direct transfer of silicon-based techniques being problematic due to material differences.
Innovation Solution
A novel edge termination structure featuring a plurality of ring portions with varying widths and junction depths, along with a metal field-plate region and field-oxide region, is implemented, allowing for a self-aligned doping process that creates a continuous and uninterrupted ring region with a variable doping profile to control the electric field effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single ring region is provided in contact with the main junction region, then the manufacturing process is simple (one mask and one dopant implantation), but the control of electric field distribution is not optimal (peaks of electric field occur at the ends of the metal region and ring region)
Solution Approach 1:
The single ring region is divided into multiple ring portions (first, second, third ring portions) with different depths and doping concentrations. This segmentation allows independent optimization of each portion's electric field contribution, enabling better overall electric field distribution control while maintaining manufacturing simplicity through a single implantation process.
Solution Approach 2:
Different ring portions are assigned different doping concentrations and depths to create locally optimized electric field profiles. The first ring portion has higher doping concentration and greater depth, while subsequent portions have progressively lower concentrations and depths, matching the local electric field requirements at different radial positions.
2Manufacturing precision
If multiple ring regions are provided with variable width and separation distance, then better control of electric field is achieved, but manufacturing complexity increases
Solution Approach 1:
The termination structure is segmented into multiple ring portions that are concentric and have different depths. This segmentation provides the flexibility to control electric field distribution through depth variation and doping concentration gradients, achieving precise field control without requiring complex lateral geometries or multiple implantation steps.
Solution Approach 2:
Instead of controlling electric field through lateral variations in ring width and separation (2D plane), the invention transitions to the depth dimension (3D), using vertically stacked ring portions at different depths. This dimensional transition simplifies the manufacturing process while maintaining precise electric field control capability.
3Ease of manufacture
If silicon-based edge termination techniques are directly transferred to silicon carbide, then manufacturing process is established, but optimal breakdown voltage is not achieved due to material differences
Solution Approach 1:
The invention adapts the termination structure parameters specifically for silicon carbide material properties. Multiple ring portions with progressively varying doping concentrations and depths are designed to match SiC's high critical electric field and wide bandgap characteristics, achieving breakdown voltages closer to theoretical limits while using manufacturing processes compatible with SiC technology.
Solution Approach 2:
The termination structure uses a composite doping profile across multiple ring portions with different materials properties (doping concentrations, depths). This composite approach optimizes the electric field distribution for silicon carbide's unique material properties, bridging the gap between manufacturability and optimal electrical performance.
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 solution enhances electrical performance by reducing electric field peaks, achieving breakdown voltages closer to theoretical values, improving reliability, and simplifying manufacturing while leveraging the unique properties of silicon carbide to maintain dopant localization.
Implementation Method 1
a first dopant implantation process is performed to dope a first ring portion, a second dopant implantation process is performed to dope a second ring portion
Implementation Method 2
a first thermal activation process is performed to diffuse the dopant in the first doped region, a second thermal activation process is performed to diffuse the dopant in the second doped region
Data Source
AI summary
An integrated device has: a structural layer of semiconductor material doped with a first conductivity type and having a top surface defining a plane; a functional region, doped with a second conductivity type, arranged in an active area of the structural layer at the top surface, in the proximity of an edge area of the integrated device, which externally surrounds the active area; and an edge termination region, doped with the second conductivity type, joined to the functional region and arranged in the edge area. The edge termination region has a doping profile and a junction depth that vary in a first direction parallel to the plane.