SiC Edge Termination Structure Impurity Gradients
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Solution Overview
Problem
Silicon carbide semiconductor devices face challenges in achieving high breakdown voltage due to electric field concentration at the boundary between JTE regions, leading to reduced manufacturing process margins and increased costs from complex processing requirements.
Innovation Solution
A semiconductor device with a concentric edge termination structure featuring alternating subregions of varying impurity concentrations, where the farther outward regions have lower impurity concentrations, and intermediate regions with specific subregion arrangements to reduce impurity concentration gradients and enhance electric field relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a JTE structure with p-type low-concentration regions is formed to relax electric field, then breakdown voltage is improved, but electric field concentrates on outer peripheral portion of p-type low-concentration region limiting breakdown voltage
Solution Approach 1:
The p-type low-concentration region is divided into multiple regions with different impurity concentrations (first, second, and third regions). This segmentation distributes the electric field relaxation function across multiple zones, preventing electric field concentration at any single location while maintaining overall breakdown voltage improvement.
Solution Approach 2:
Different regions within the p-type low-concentration structure have different impurity concentrations tailored to their specific locations. The first region has higher concentration near the pn junction, the second region has intermediate concentration in the middle, and the third region has lower concentration at the periphery. This local quality variation optimizes electric field distribution throughout the structure.
2Reliability
If multiple p-type low-concentration regions with different impurity concentrations are formed adjacently, then electric field relaxation is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent varies the impurity concentration parameter across different regions (first, second, and third regions) to achieve electric field relaxation. By controlling only the impurity concentration parameter in adjacent regions, the structure achieves complex electric field management without introducing additional geometric complexity or multiple processing steps.
3Productivity
If ion implantation with high acceleration voltage is used to introduce impurities, then impurity introduction efficiency is improved, but thermal diffusion of impurities is extremely small making VLD structure difficult to apply
Solution Approach 1:
Instead of relying on thermal diffusion to create a continuous gradient, the patent segments the impurity distribution into discrete regions (first, second, and third regions) with different concentrations. This segmentation approach is compatible with ion implantation methods, as each region can be formed by controlled implantation doses, achieving the desired concentration profile without requiring extensive thermal diffusion.
4Strength
If the number of p-type low-concentration regions is increased to reduce impurity concentration difference, then breakdown voltage performance is improved, but manufacturing cost increases due to increased number of processes
Solution Approach 1:
The patent achieves improved breakdown voltage performance by creating only three distinct regions (first, second, and third regions) with progressively varying impurity concentrations, rather than requiring many more regions with small concentration differences. This three-region approach with clear parameter variations is much more manufacturable while still achieving the desired electric field relaxation and high breakdown voltage 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 configuration effectively increases the breakdown voltage of the edge termination structure without increasing the edge termination structure's width, thereby reducing manufacturing costs and improving reliability.
Implementation Method 1
An intermediate region of the second conductivity type, disposed so as to mutually contact one combination of the semiconductor regions that are adjacent, the intermediate region having an impurity concentration that is lower than that of the semiconductor region adjacent on an inner side and an impurity concentration that is higher than that of the semiconductor region adjacent on an outer side
Data Source
AI summary
In an edge termination structure portion, first and second JTE regions are disposed concentrically surrounding an active region. Between the first and second JTE regions, a p-type electric field relaxation region is disposed that includes a first subregion and a second subregion alternately and repeatedly arranged concentrically surround a periphery of the first JTE region. An average impurity concentration of the electric field relaxation region is higher that the impurity concentration of the first JTE region adjacent on the inner side and lower than the impurity concentration of the second JTE region adjacent on the outer side. First subregions have widths that decrease the farther outward they are arranged. Second subregions have widths that are substantially the same independent of position. The first subregions and the first JTE region have equal impurity concentrations. The second subregions and the second JTE region have equal impurity concentrations.