SiC Avalanche Control via Localized Doping
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Solution Overview
Problem
Wide bandgap semiconductor devices face challenges in controlling avalanche breakdown, as dopant diffusion in these materials is slow, leading to preferential breakdown at the edges due to high electric fields, rather than a uniform distribution across the active region.
Innovation Solution
A wide bandgap semiconductor device with a lightly doped layer and specific conductivity type regions, including a Schottky barrier region, is designed to control avalanche breakdown by varying dopant concentrations, ensuring it occurs in the active region rather than the termination region, using ion implantation to form regions with higher dopant concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopant diffusion is used to create regions with different breakdown voltages, then breakdown can be controlled to occur in the active region, but the process is very slow and difficult to fabricate deep structures in wide bandgap semiconductors
Solution Approach 1:
The dopant regions are pre-formed during the epitaxial growth process before device operation, rather than attempting to diffuse dopants after fabrication. This preliminary action allows deep doped regions to be created efficiently in wide bandgap materials where diffusion is extremely slow, enabling breakdown voltage control without lengthy thermal diffusion processes
Solution Approach 2:
The invention changes the approach from post-fabrication dopant diffusion to in-situ dopant incorporation during epitaxial growth. By changing the fabrication parameter from thermal diffusion to controlled doping during crystal growth, deep doped regions can be created rapidly while maintaining precise control over breakdown characteristics
2Object-affected harmful factors
If edge termination structures are used to smooth discontinuities, then large electric fields at edges are reduced, but breakdown still occurs preferentially at edges rather than uniformly distributed over the active area
Solution Approach 1:
The invention creates locally doped regions (first and second doped regions) with different dopant concentrations positioned at specific locations within the active region. These localized doped areas modify the electric field distribution locally, ensuring that breakdown occurs uniformly across the active region rather than concentrating at edges, even after edge termination structures smooth the edge discontinuities
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 design effectively disperses avalanche current across the active region, reducing edge-related breakdown and increasing the device's ruggedness by distributing the breakdown voltage more uniformly, thus enhancing the device's operational reliability and thermal characteristics.
Implementation Method 1
a first metal layer on the first surface of the lightly doped layer, the first metal layer and the first surface forms a Schottky barrier region where the first metal layer contacts areas of the first conductivity type
Implementation Method 2
Dopant diffusion in wide bandgap semiconductors such as silicon carbide (SiC) is very slow, making it difficult to fabricate deep structures
Implementation Method 3
using ion implantation to form regions with higher dopant concentrations
Implementation Method 4
Avalanche breakdown is the phenomenon of current multiplication when a semiconductor device is subject to high electric fields
Data Source
AI summary
A wide bandgap silicon carbide device has an avalanche control structure formed in an epitaxial layer of a first conductivity type above a substrate that is connected to a first electrode of the device. A first region of a second conductivity type is in the upper surface of the epitaxial layer with a connection to a second electrode of the device. A second region of the first conductivity type lies below the first region and has a dopant concentration greater than the dopant concentration in the epitaxial layer.