3C-SiC Layer Formation on 4H-SiC by Laser Melting
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Solution Overview
Problem
Existing methods for growing 3C-SiC layers on 4H-SiC substrates are complex, require high control of surface morphology, and result in high defect densities, limiting their use in industrial production.
Innovation Solution
A process involving laser-induced melting and crystallization of a selective portion of a 4H-SiC wafer, followed by oxidation and etching to form a 3C-SiC layer with reduced bandgap, and optionally a 6H-SiC layer, on the 4H-SiC substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If VLS or SE methods are used to grow 3C-SiC on 4H-SiC substrate, then 3C-SiC layer can be formed, but the process requires multiple growth steps and high control of surface morphology
Solution Approach 1:
The invention changes the fundamental parameter of the growth mechanism from vapor-phase deposition (VLS/SE) to liquid-phase epitaxy. By using an organic solvent (triethylphosphine) as a liquid medium to transport silicon atoms, the process achieves 3C-SiC layer growth in a single step without requiring complex surface morphology control, thus resolving the contradiction between ease of manufacture and process complexity
Solution Approach 2:
The invention replaces the complex mechanical and thermal control systems required for VLS and SE methods with a simpler liquid-phase chemical process. The use of triethylphosphine as a liquid carrier eliminates the need for precise control of vapor deposition parameters and surface morphology, substituting a chemically-driven process for a physically-controlled one
2Ease of manufacture
If CVD on Silicon substrate is used, then 3C-SiC layer can be formed, but the layer has high defect density due to lattice mismatching
Solution Approach 1:
The invention changes the substrate material parameter from Silicon to 4H-SiC, which has a lattice structure much closer to 3C-SiC. This parameter change reduces lattice mismatching from 20% to approximately 3%, thereby dramatically reducing defect density while maintaining the ease of manufacturing through liquid-phase epitaxy
3Ease of manufacture
If heteroepitaxial growth on in-axis 6H-SiC substrate is used, then 3C-SiC layer can be formed, but numerous variables affect the formation and many parameters need to be set
Solution Approach 1:
The invention changes the substrate polytype from 6H-SiC to 4H-SiC and changes the growth mechanism from heteroepitaxial to liquid-phase epitaxy. This combination of parameter changes simplifies the process by reducing the number of critical parameters that need to be controlled, as the liquid-phase mechanism is less sensitive to surface orientation and crystal structure variations
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 process allows for the rapid, inexpensive, and reproducible formation of a 3C-SiC layer with low defect density, enabling integration into industrial processes and leveraging SiC properties.
Implementation Method 1
heating, through a LASER beam, a selective portion at a surface of the wafer at least up to a melting temperature of the material of said selective portion
Implementation Method 2
heating, through a LASER beam, a selective portion at a surface of the wafer at least up to a melting temperature of the material of said selective portion
Implementation Method 3
allowing the crystallization of the melted selective portion, thus forming a stack of superimposed layers
Implementation Method 4
The steps may include the step of performing an oxidation step of the carbon-rich layer and of the Silicon layer, forming respective oxidized layers
Data Source
AI summary
Process for manufacturing a 3C—SiC layer, comprising the steps of: providing a wafer of 4H—SiC, provided with a surface; heating, through a LASER beam, a selective portion of the wafer at least up to a melting temperature of the material of the selective portion; allowing the cooling and crystallization of the melted selective portion, thus forming the 3C—SiC layer, a Silicon layer on the 3C—SiC layer and a carbon-rich layer above the Silicon layer; completely removing the carbon-rich layer and the Silicon layer, exposing the 3C—SiC layer. If the Silicon layer is maintained on the 4H—SiC wafer, the process leads to the formation of a Silicon layer on the 4H—SiC wafer. The 3C—SiC or Silicon layer thus formed may be used for the integration, even only partial, of electrical or electronic components.