Monocrystalline SiC Thin-Layer Transfer via Amorphous Carrier Crystallization
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Solution Overview
Problem
The challenge lies in manufacturing high-quality composite structures with thin layers of monocrystalline silicon carbide (c-SiC) on silicon carbide support substrates, particularly poly-crystalline SiC, while avoiding defects and the complexity of achieving direct bonding with molecular adhesion, which affects the electrical conduction and reliability of power devices.
Innovation Solution
A method involving epitaxial growth of a donor layer with reduced crystal defects, ion implantation to form a buried fragile plane, chemical vapor deposition of a support layer at low temperatures, separation along the buried plane, and subsequent heat treatment to crystallize the support substrate, ensuring high-quality c-SiC layers with improved electrical and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct bonding is attempted between c-SiC and p-SiC substrates, then molecular adhesion is achieved, but surface roughness management becomes complex and bonding quality deteriorates
Solution Approach 1:
The patent introduces an intermediate amorphous SiC layer deposited by CVD as a mediator between the c-SiC layer and p-SiC substrate. This intermediate layer simplifies the bonding process by providing a compliant interface that tolerates surface roughness variations, eliminating the need for complex surface roughness management while achieving reliable molecular adhesion through subsequent laser annealing.
Solution Approach 2:
The patent changes the physical state of the intermediate SiC layer from crystalline to amorphous through controlled CVD deposition at lower temperatures, then transforms it back to crystalline through laser annealing. This parameter change (crystalline↔amorphous transition) enables the layer to serve dual functions: providing bonding compliance in amorphous state and ensuring electrical conductivity in crystalline state.
2Strength
If argon bombardment is used for surface activation bonding, then bonding energy increases, but an amorphous layer forms that adversely impacts vertical electrical conduction
Solution Approach 1:
The patent converts the harmful effect of amorphous layer formation into a beneficial process by intentionally creating an amorphous SiC intermediate layer through CVD deposition, then using laser annealing to crystallize it. The amorphous state facilitates compliant bonding, while the subsequent crystallization restores electrical conductivity, turning the potential defect into a functional advantage.
Solution Approach 2:
The patent replaces the mechanical argon bombardment method with a chemical vapor deposition approach followed by thermal annealing. Instead of using mechanical sputtering to activate surfaces, the process uses controlled chemical deposition to create the intermediate layer, then uses thermal energy from laser annealing to crystallize it, achieving both bonding and electrical conductivity without the harmful amorphous layer.
3Reliability
If high temperature processing is used for p-SiC manufacture, then material properties are achieved, but cavity growth in buried fragile plane causes blistering
Solution Approach 1:
The patent performs preliminary actions by depositing the amorphous SiC intermediate layer and forming the complete stack structure before applying high temperature processing. The intermediate layer acts as a buffer that accommodates cavity growth during low-temperature deposition, preventing blistering when subsequent high-temperature annealing is applied for crystallization and bonding.
Solution Approach 2:
The patent creates a composite structure consisting of c-SiC layer, amorphous SiC intermediate layer, and p-SiC substrate. This composite material structure allows each layer to serve its specific function: the c-SiC provides electrical conductivity, the amorphous SiC provides bonding compliance and cavity accommodation, and the p-SiC substrate provides mechanical support, collectively preventing blistering during high-temperature processing.
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 approach enables the production of composite structures with enhanced electrical conductivity, thermal conductivity, and reduced defect density, addressing the limitations of existing methods and ensuring the reliability and performance of power devices.
Implementation Method 1
growing by epitaxy of a donor layer of monocrystalline silicon carbide on the initial substrate
Implementation Method 2
ion implantation of light species in the donor layer, to form a buried fragile plane
Implementation Method 3
chemical vapor deposition step assisted by direct liquid injection, at a temperature below 1000°C, to form a support layer directly on the free surface of the donor layer
Implementation Method 4
heat treatment step at a temperature between 1000°C and 1800°C, applied to the intermediate composite structure, to crystallize the support layer and form the poly-crystalline support substrate
Data Source
Figure 1~2b
Figure 2c~2e
Figure 2f~3b
AI summary
The invention concerns a method for manufacturing a composite structure comprising a thin layer of monocrystalline silicon carbide arranged on a silicon carbide carrier substrate, the method comprising: a) a step of providing an initial substrate made from monocrystalline silicon carbide, b) a step of epitaxial growth of a monocrystalline silicon carbide donor layer on the initial substrate, in order to form a donor substrate, c) a step of ion implantation of light species in the donor layer, in order to form a buried fragile plane delimiting the thin layer between the buried fragile plane and a free surface of the donor layer, d) a step of direct liquid injection chemical vapour deposition, at a temperature lower than 1000°C, in order to form a carrier layer directly on the free surface of the donor layer, the carrier layer being formed by an at least partially amorphous SiC matrix, e) a step of separation along the buried fragile plane, in order to form an intermediate composite structure comprising the thin layer on the carrier layer, and the rest of the donor substrate, f) a heat treatment step at a temperature of between 1000°C and 1800°C, applied to the intermediate composite structure, in order to crystallise the carrier layer and form the polycrystalline carrier substrate, g) a step of mechanical and/or chemical treatment(s) of the composite structure.