Floating Field Ring Termination for SiC Devices
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Solution Overview
Problem
High power semiconductor devices face challenges in achieving efficient edge termination structures that balance breakdown voltage and wafer area, particularly in silicon carbide (SiC) devices, where the number of floating field rings required for high voltage applications reduces the active area available for current handling.
Innovation Solution
A high power semiconductor device with a floating field ring termination structure featuring a low-doped surface layer and enhanced doping regions that increase electric field coupling between floating field rings, allowing for reduced separation distances and area-efficient design, thereby enhancing breakdown voltage while maintaining a compact form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of floating field rings is increased to achieve high breakdown voltage (6 to 10 kV), then the breakdown voltage capability is improved, but the occupied wafer area increases significantly, reducing the active area available for current handling
Solution Approach 1:
The patent changes the doping concentration parameter in the drift layer, creating a low-doped surface layer with reduced doping concentration compared to the bulk drift layer. This parameter change modifies the electric field distribution and coupling between floating field rings, enabling fewer rings (3 to 15) to achieve the same breakdown voltage capability that would otherwise require 30 to 50 rings, thus resolving the contradiction between breakdown voltage capability and wafer area occupation.
2Area of stationary object
If the separation distance between floating field rings is reduced to improve area efficiency, then the occupied wafer area is reduced, but the electric field coupling between rings deteriorates, affecting breakdown voltage performance
Solution Approach 1:
The patent modifies the doping concentration parameter in the drift layer to create a low-doped surface layer, which enhances the electric field coupling between floating field rings. This parameter change allows for reduced separation distances between rings while maintaining effective electric field coupling, thereby resolving the contradiction between area efficiency and electric field coupling performance.
3Area of stationary object
If the width of floating field rings in the lateral direction is reduced to increase active area, then the available active area is increased, but the ability to alleviate field crowing at edges is reduced
Solution Approach 1:
The patent changes the doping concentration parameter in the drift layer to create a low-doped surface layer that extends to the surface. This parameter change enhances the electric field distribution and coupling, enabling thinner floating field rings to effectively alleviate field crowing at edges while maximizing the active area, thus resolving the contradiction between active area and field crowing alleviation capability.
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 solution achieves a high breakdown voltage with reduced area requirements, optimizing the electric field distribution and preventing punch-through breakdown, thus improving the area efficiency and current handling capability of high power semiconductor devices.
Implementation Method 1
The low-doped surface layer with the reduced doping concentration greatly enhances the electric field coupling from floating field ring to floating field ring
Implementation Method 2
the enhanced doping regions respectively act as an electric field stop region allowing a higher electric field close to the blocking pn-junction
Data Source
AI summary
A high power semiconductor device with a floating field ring termination includes a wafer, wherein a plurality of floating field rings is formed in an edge termination region adjacent to a first main side surface of the wafer. At least in the termination region a drift layer, in which the floating field rings are formed, includes a surface layer and a bulk layer wherein the surface layer is formed adjacent to the first main side surface to separate the bulk layer from the first main side surface and has an average doping concentration which is less than 50% of the minimum doping concentration of the bulk layer. The drift layer includes a plurality of enhanced doping regions, wherein each one of the enhanced doping regions is in direct contact with a corresponding one of the floating field rings at least on a lateral side of this floating field ring, which faces towards the active region. The relatively low doped surface layer and the enhanced doping regions increase the electric field coupling from floating field ring to floating field ring, thus allowing an area efficient termination structure. Each enhanced doping region extends to at least the same depth as the one of the corresponding floating field ring.