SiC Semiconductor Device Asymmetrical Periphery Design
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Solution Overview
Problem
In silicon carbide semiconductor devices, the asymmetrical crystal plane orientation leads to varying breakdown electric field strengths, resulting in premature breakdown and reduced yield due to defects, especially on inclined substrate regions.
Innovation Solution
A silicon carbide semiconductor device with a silicon carbide inclined substrate and conductivity type regions is designed, where the periphery is formed to minimize electric field components that cause avalanche breakdown, reducing defect probability and extending device life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a symmetrical element structure is formed on an inclined SiC substrate, then the element layout appears symmetrical when viewed from above, but the breakdown electric field strength becomes asymmetrical due to crystal plane orientation, causing premature breakdown on one side
Solution Approach 1:
The patent applies asymmetry by intentionally designing the element structure to be asymmetrical in three-dimensional space, specifically by adjusting the shape of the semiconductor region so that the sidewalls form different angles with the crystal plane. This compensates for the substrate inclination and ensures uniform breakdown characteristics across all sidewalls, resolving the contradiction between apparent symmetrical layout and actual breakdown voltage uniformity.
2Ease of manufacture
If an inclined substrate is used for SiC epitaxial growth, then the crystal growth conditions are satisfied, but the asymmetrical crystal plane orientation causes varying breakdown electric field strengths and increases defect impact
Solution Approach 1:
The patent applies local quality by making the element structure non-uniform in specific regions. The semiconductor region is designed with different dimensional characteristics on different sides, specifically with sidewalls forming different angles with the crystal plane depending on their orientation relative to the substrate inclination. This localized structural adjustment compensates for the substrate inclination effects and ensures uniform breakdown characteristics.
3Productivity
If defects are present in the SiC substrate, then the manufacturing process is affected, but defects located on regions with lower breakdown voltage cause premature breakdown and reduce device yield
Solution Approach 1:
The patent applies beforehand cushioning by designing the element structure to have uniform breakdown characteristics across all regions before defects can cause problems. By ensuring that the breakdown voltage is consistent throughout the device through asymmetrical structural design, the patent prevents defects from causing premature breakdown, thereby protecting device yield without affecting manufacturing throughput.
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 effectively suppresses avalanche breakdown, reduces defects, and improves the yield of silicon carbide semiconductor devices by optimizing the crystal plane orientation and structure of the conductivity type regions.
Implementation Method 1
an electric field component of the same direction as the plane orientation of a prescribed crystal plane based on avalanche breakdown is smaller than an electric field component of a direction different from the plane orientation of the crystal plane
Data Source
AI summary
On a major surface of an n-type silicon carbide inclined substrate (2) is formed an n-type voltage-blocking layer (3) made of silicon carbide by means of epitaxial growth. On the n-type voltage-blocking layer (3) is formed a p-type silicon carbide region (4) rectangular when viewed from above. On the surface of the p-type silicon carbide region (4) is formed a p-type contact electrode (5). In the p-type silicon carbide region (4), the periphery of the p-type silicon carbide region (4) that is parallel with a (11-20) plane (14a) of the silicon carbide crystal, which is liable to cause avalanche breakdown, is located on the short side. In this manner, the dielectric strength of a silicon carbide semiconductor device can be improved.