Silicon Carbide Epitaxial Substrate for Particle-Controlled Breakdown Voltage
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Solution Overview
Problem
Existing silicon carbide semiconductor devices face issues with breakdown voltage deterioration due to particle contamination in epitaxial layers.
Innovation Solution
A silicon carbide epitaxial substrate is manufactured with a specific ratio of particle densities in two layers, where the first layer has a first conductivity type and the second layer has a second conductivity type, formed at different temperatures in separate reaction chambers to control particle deposition and suppress breakdown voltage degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If particles are present in the epitaxial layer, then the epitaxial layer can be formed, but breakdown voltage deteriorates
Solution Approach 1:
The patent applies preliminary action by forming a first epitaxial layer with controlled particle density before forming the second epitaxial layer. The first layer serves as a preparatory structure that establishes a specific particle distribution pattern, which then influences the particle density in the second layer. This sequential approach allows control over final particle contamination levels while maintaining breakdown voltage performance.
Solution Approach 2:
The patent changes physical parameters by controlling the density distribution of particles in different epitaxial layers. Specifically, it establishes that the ratio of particle density in the first layer to particle density in the second layer should be between 0.5 and 2.0. This parameter control transforms the harmful effect of particles into a manageable design variable that maintains reliability.
2Reliability
If particle density is reduced in the epitaxial layer, then breakdown voltage is maintained, but manufacturing complexity increases
Solution Approach 1:
The patent segments the epitaxial layer formation into two distinct stages: forming a first epitaxial layer with specific particle density, then forming a second epitaxial layer with controlled particle density. This segmentation allows independent optimization of particle distribution in each layer, achieving the desired particle density ratio (0.5-2.0) while providing clear manufacturing guidelines that reduce overall process complexity.
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 method effectively suppresses breakdown voltage deterioration by controlling particle density and distribution, enhancing the performance and reliability of silicon carbide semiconductor devices.
Implementation Method 1
forming a first silicon carbide epitaxial layer on a silicon carbide substrate in a first reaction chamber at a first temperature
Implementation Method 2
heating the silicon carbide substrate on which the first silicon carbide epitaxial layer is formed, in the second reaction chamber at a second temperature while allowing a gas to flow
Implementation Method 3
forming a second silicon carbide epitaxial layer on the first silicon carbide epitaxial layer in the second reaction chamber
Data Source
AI summary
A silicon carbide epitaxial substrate according to the present disclosure includes: a silicon carbide substrate; a first silicon carbide epitaxial layer disposed on the silicon carbide substrate; and a second silicon carbide epitaxial layer disposed on the first silicon carbide epitaxial layer. When an area density of first particles in the first silicon carbide epitaxial layer is defined as a first area density and an area density of second particles in the second silicon carbide epitaxial layer is defined as a second area density, a value determined by dividing the first area density by the second area density is more than 0.5 and less than 1. The first particles and the second particles each have a maximum diameter of 2 μm to 50 μm.