Single-Crystal SiC Layer Transfer on Polycrystalline SiC Carriers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The high cost and limited availability of high-quality single-crystal silicon carbide (SiC) substrates for microelectronics hinder the development of vertically integrated power devices with high power density, necessitating alternative layer transfer solutions for fabricating composite structures with thin layers of single-crystal SiC on polycrystalline SiC carrier substrates.
Innovation Solution
A process involving porosification of the initial single-crystal SiC substrate, deposition of an amorphous silicon carbide layer, direct bonding with a polycrystalline SiC carrier substrate, heat treatment for crystallization, and separation in the porous layer to form a composite structure with a thin layer of single-crystal SiC, accompanied by mechanical and chemical treatments to refine the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-quality single-crystal SiC substrates are used, then the quality of the thin layer is improved, but the cost increases and availability decreases
Solution Approach 1:
The process segments the single-crystal SiC substrate into a thin layer that is separated from the bulk substrate. The thin layer is then transferred to a polycrystalline SiC carrier substrate, allowing the high-quality crystalline structure to be preserved in the thin layer while using a lower-cost polycrystalline carrier.
Solution Approach 2:
A porous layer is introduced as an intermediary structure between the single-crystal SiC substrate and the polycrystalline SiC carrier substrate. This porous layer facilitates the transfer process by allowing the thin layer to be grown epitaxially and then separated, enabling the transfer of high-quality material to a lower-cost carrier.
2Power
If vertical components are fabricated, then power density is improved, but the requirement for high-quality single-crystal substrates increases
Solution Approach 1:
The process applies local quality by creating a thin layer with single-crystal structure (high quality) only where needed for the active regions, while the carrier substrate can be polycrystalline (lower quality). This allows vertical component fabrication with high power density while reducing the overall substrate quality requirements.
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 process enables the cost-effective production of composite structures with high-quality thin single-crystal SiC layers on polycrystalline SiC substrates, facilitating vertical electrical conduction and reducing material costs while maintaining mechanical strength and crystalline integrity.
Implementation Method 1
a step of porosification applied to the initial substrate, in order to form a porous layer at least on the front face side of the initial substrate
Implementation Method 2
a step of forming a superficial layer made of amorphous silicon carbide, on the front face of the carrier substrate and/or on the porous layer
Implementation Method 3
a step of joining the initial substrate and the carrier substrate at their respective front faces
Implementation Method 4
a heat treatment step applied to the first intermediate structure, at a temperature above 900° C., in order to crystallize the surface layer, at least partly in the form of single-crystal silicon carbide, starting from a contact interface with the porous layer
Implementation Method 5
a step of separation in the porous layer of the second intermediate structure, in order to obtain the composite structure on the one hand and the remainder of the initial substrate on the other hand
Data Source
AI summary
A method of fabricating a composite structure including a thin layer of single-crystal silicon carbide on a polycrystalline silicon carbide carrier substrate includes providing an initial substrate of single-crystal silicon carbide and a carrier substrate of polycrystalline silicon carbide. A porous layer is formed on the initial substrate, and a superficial layer of amorphous silicon carbide is formed on the carrier substrate and/or on the porous layer. The initial substrate and the carrier substrate are joined to form a first intermediate structure, which is heat treated at an elevated temperature to crystallize the superficial layer, at least partly in the form of single-crystal silicon carbide, to form the thin layer and to form a second intermediate structure, which is separated in the porous layer to form the composite structure and a remainder of the initial substrate.