GaN Edge Termination Guard Ring for Breakdown Voltage
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Solution Overview
Problem
Conventional power semiconductor devices face limitations in achieving high breakdown voltage due to electric field crowding at the edges, leading to reduced operational efficiency and increased manufacturing costs, especially when using silicon or silicon carbide substrates for gallium-nitride layers.
Innovation Solution
The method involves forming edge termination structures using trench and refill techniques or ion implantation in gallium-nitride (GaN) based epitaxial layers to create insulating regions that electrically isolate device regions from edge termination regions, allowing for the use of GaN substrates with pseudo-bulk characteristics, thereby reducing electric field crowding and enhancing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silicon or silicon carbide substrates are used for gallium-nitride layers, then manufacturing experience and existing infrastructure are leveraged, but electric field crowding at edges occurs leading to reduced breakdown voltage
Solution Approach 1:
The patent applies local quality by creating a guard ring structure with different doping characteristics at the edge termination region compared to the active device region. The guard ring is formed with a specific doping concentration and depth that differs from the bulk drift region, allowing the edge area to have optimized electrical properties that prevent field crowding while maintaining high breakdown voltage.
Solution Approach 2:
The guard ring acts as an intermediary structure between the active device region and the edge termination region. It mediates the electric field distribution by providing a transition zone with controlled doping that prevents direct field crowding at the edges, thereby protecting the overall device breakdown voltage.
2Reliability
If edge termination structures are implemented to reduce electric field crowding, then breakdown voltage improves, but device complexity and manufacturing steps increase
Solution Approach 1:
The device is segmented into distinct regions: an active device region, a guard ring region, and an edge termination region. The guard ring is formed as a separate segmented structure with specific doping parameters that differ from adjacent regions, allowing independent optimization of each zone's electrical characteristics to achieve high breakdown voltage.
Solution Approach 2:
The guard ring is formed preliminarily during the epitaxial growth process before final device completion. By establishing the guard ring structure early in manufacturing with controlled doping during epitaxy, subsequent processing steps are simplified, and the overall device fabrication complexity is reduced despite the added functional complexity.
3Object-generated harmful factors
If insulating regions are formed to electrically isolate device regions from edge termination regions, then off-state leakage current reduces, but manufacturing precision requirements increase
Solution Approach 1:
The insulating effect is achieved through self-service by utilizing the natural properties of the guard ring structure and edge termination design. The specific doping concentration and depth of the guard ring, combined with the edge termination geometry, inherently create the necessary electrical isolation without requiring additional insulating materials or complex isolation structures, thereby reducing manufacturing precision demands.
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 results in semiconductor devices that achieve a significant percentage of ideal parallel-plane breakdown voltage, are fully or substantially planar, and consume less area, while being less expensive to manufacture, with reduced off-state leakage current and improved operational efficiency.
Implementation Method 1
forming an insulating region in a first portion of the first GaN epitaxial layer. The insulating region extends vertically through at least 90% of the first GaN epitaxial layer to separate an active device region of the first GaN epitaxial layer from an outer region of the first GaN epitaxial layer
Implementation Method 2
ion implantation into gallium-nitride (GaN) based epitaxial layers to electrically isolate device regions from edge termination regions
Data Source
AI summary
A method for fabricating an edge termination, which can be used in conjunction with GaN-based materials, includes providing a substrate of a first conductivity type. The substrate has a first surface and a second surface. The method also includes forming a first GaN epitaxial layer of the first conductivity type coupled to the first surface of the substrate and forming a second GaN epitaxial layer of a second conductivity type opposite to the first conductivity type. The second GaN epitaxial layer is coupled to the first GaN epitaxial layer. The substrate, the first GaN epitaxial layer and the second GaN epitaxial layer can be referred to as an epitaxial structure.