Double Guard Ring Termination for SiC Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional edge termination techniques for silicon carbide (SiC) devices, such as junction termination extension (JTE) and multiple floating guard rings (MFGR), are sensitive to implant dose variations and surface charges, leading to reliability issues and increased fabrication costs, and are not suitable for high-voltage SiC devices due to high electric fields and oxide quality concerns.
Innovation Solution
The implementation of a double guard ring termination structure with highly doped and lightly doped portions, where the highly doped portion is achieved by Aluminum implants and the lightly doped portion by Boron implants, providing a doping gradient from the main junction to the termination edge to reduce electrical fields, and using a surface charge compensation layer to neutralize oxide-semiconductor interface charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional JTE or MFGR termination techniques are used, then edge termination is achieved, but sensitivity to implant dose variations and surface charges increases, leading to reliability issues
Solution Approach 1:
The patent applies parameter changes by modifying the doping concentration parameter across different regions. The guard ring structure incorporates both lightly doped regions (1e16 to 1e18 atoms/cm³) and heavily doped regions (1e19 to 1e21 atoms/cm³), creating a gradient that makes the termination less sensitive to implant dose variations while maintaining reliability
Solution Approach 2:
The termination structure is segmented into multiple functional regions: lightly doped guard rings, heavily doped guard rings, and a surface charge compensation layer. This segmentation allows each region to perform its specific function independently, reducing the overall sensitivity to manufacturing variations
2Reliability
If multiple floating guard rings are added to reduce sensitivity to implant dose variation, then reliability improves, but the area utilized for termination increases to almost three times the area of JTE alone
Solution Approach 1:
The patent merges multiple functions into a compact structure. The guard rings serve both as field management elements and as the primary termination structure, eliminating the need for separate JTE regions. The surface charge compensation layer is integrated directly at the oxide-semiconductor interface, combining charge compensation with the termination function in a space-efficient manner
Solution Approach 2:
Different regions of the termination structure have different doping qualities - lightly doped regions for field management, heavily doped regions for charge compensation, and specific regions optimized for different functions. This local differentiation allows compact sizing while maintaining reliability
3Ease of manufacture
If field plates are used for edge termination, then fabrication cost is reduced, but high oxide fields result due to oxide-semiconductor interface charges, causing long-term reliability problems
Solution Approach 1:
The patent converts the harmful effect of oxide-semiconductor interface charges into a beneficial feature. Instead of trying to eliminate these charges, the heavily doped guard ring regions are specifically designed to attract and compensate for the positive interface charges, creating a negative space charge region that neutralizes the harmful field enhancement at the interface
Solution Approach 2:
The heavily doped guard ring regions act as intermediaries between the lightly doped drift region and the oxide-semiconductor interface. These intermediate regions with high doping concentrations (1e19 to 1e21 atoms/cm³) provide a transition zone that manages the field distribution and compensates for interface charges, protecting the main device structure
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 enhances the blocking capability and reliability of SiC devices by reducing electrical fields and increasing the maximum breakdown voltage, while being more tolerant to processing variations and oxide quality issues, thus improving the overall performance and yield of high-voltage SiC devices.
Implementation Method 1
The spaced apart concentric floating guard rings have a highly doped portion and a lightly doped portion... providing a doping gradient from the main junction to the termination edge to reduce electrical fields
Implementation Method 2
using a surface charge compensation layer to neutralize oxide-semiconductor interface charges
Data Source
AI summary
Edge termination structures for semiconductor devices are provided including a plurality of spaced apart concentric floating guard rings in a semiconductor layer that at least partially surround a semiconductor junction. The spaced apart concentric floating guard rings have a highly doped portion and a lightly doped portion. Related methods of fabricating devices are also provided herein.