SiC Semiconductor Contact Resistance via Oblique 3C Polytype Layer
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Solution Overview
Problem
Semiconductor devices with SiC substrates face high contact resistance at ohmic junctions between the substrate and electrodes, limiting electron mobility and device performance.
Innovation Solution
Forming a 3C polytype layer that extends obliquely from the surface of a 4H or 6H polytype SiC substrate, allowing electrons to move rapidly through a narrower passageway, leveraging the quantum wire effect to reduce contact resistance, and using a manufacturing method involving ion injection and heat treatment to create these layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 3C polytype layer is epitaxially grown uniformly on the SiC substrate surface, then the contact resistance is reduced due to lower bandgap, but the electron passageway width increases causing more scattering and lower electron mobility
Solution Approach 1:
The patent applies local quality by creating a 3C polytype layer with oblique extension from the substrate surface, forming a wedge-shaped structure where the layer thickness varies locally. This creates different properties at different locations: the thin region provides narrow passageway for high electron mobility, while the 3C polytype material throughout provides low bandgap for reduced contact resistance.
Solution Approach 2:
The patent transitions from a conventional uniform planar 3C layer to an obliquely extending structure that adds a depth dimension. The 3C polytype layer extends from the surface inward at an angle, creating a three-dimensional wedge shape that narrows the electron passageway in the vertical direction while maintaining lateral coverage, thus resolving the contradiction between contact resistance and electron mobility.
2Quantity of substance
If the 3C polytype layer thickness is increased to reduce contact resistance, then more electrons can flow to the electrode, but the passageway width increases reducing electron speed
Solution Approach 1:
The oblique extension of the 3C polytype layer into the depth direction of the substrate creates a wedge-shaped structure. This three-dimensional configuration allows the layer to provide sufficient contact area for electron flow quantity while maintaining a narrow thickness in the electron transport direction, thus preserving high electron speed through the quantum wire effect.
Solution Approach 2:
The patent creates a composite structure combining 3C polytype layer with the underlying 4H or 6H polytype SiC substrate. The 3C layer provides low bandgap regions for electron injection, while the oblique geometry ensures narrow passageways, and the substrate provides mechanical support and additional electron supply, achieving both high electron quantity and speed.
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 obliquely extending 3C polytype layer reduces contact resistance by increasing electron mobility, allowing electrons to flow at speeds close to theoretical values, thereby enhancing the performance of semiconductor devices like Schottky diodes and MOSFETs.
Implementation Method 1
the width of the passageway of the electrons (the width of a cross-section cut across the direction of flow of the electrons) is large. The larger the width of the passageway of the electrons, the more the scattering factors in the electrons increases. For that reason, the larger the width of the passageway of the electrons, the slower the speed of the electrons. The speed of the electrons may be referred to as the electron mobility. To express that conversely, the scattering factors of the electron decrease as their passageway becomes narrower, and so the narrower the passageway of the electrons, the nearer the substantial speed of electrons to the theoretical electron mobility. This effect is called the 'quantum wire effect'.
Implementation Method 2
a manufacturing method involving ion injection and heat treatment to create these layers
Implementation Method 3
a manufacturing method involving ion injection and heat treatment to create these layers
Data Source
AI summary
A semiconductor device is provided in which the contact resistance of the interface between an electrode and the semiconductor substrate is reduced. The semiconductor device includes a 4H polytype SiC substrate, and an electrode formed on a surface of the substrate. A 3C polytype layer, which extends obliquely relative to the surface of the substrate and whose end portion at the substrate surface is in contact with the electrode, is formed at the surface of the substrate. The 3C polytype layer has a lower bandgap than 4H polytype. Hence, electrons present in the 4H polytype region pass through the 3C polytype layer and reach the electrode. More precisely, the width of the passageway of the electrons is determined by the thickness of the 3C polytype layer. Consequently, with this semiconductor device, in which the passageway of the electrons is narrow, the electrons are able to reach the electrode at a speed close to the theoretical value, by the quantum wire effect. In this way, the contact resistance can be reduced in the semiconductor device.