Monocrystalline SiC Thin-Layer Transfer on Polycrystalline SiC
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Solution Overview
Problem
The production of high-quality composite structures with a thin layer of monocrystalline silicon carbide (c-SiC) on a carrier substrate is hindered by challenges such as high costs, complexity, and the presence of extended defects, which affect the performance and reliability of power devices, particularly due to difficulties in achieving high-quality direct bonding and managing surface roughness and thermal expansion coefficients.
Innovation Solution
A process involving epitaxial growth of a donor layer with reduced crystal defect density, ion implantation to form a buried brittle plane, deposition of a carrier substrate at controlled temperatures, and mechanical/chemical treatments to achieve a high-quality composite structure with improved electrical conductivity and reduced defect density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct bonding is used to assemble monocrystalline SiC thin layer on polycrystalline SiC carrier substrate, then vertical electrical conduction is enabled, but high-quality bonding is difficult to achieve due to complex surface roughness and surface condition management
Solution Approach 1:
The patent applies preliminary action by performing ion implantation and annealing treatments on the donor substrate before bonding to pre-condition the surfaces. This creates a controlled interface structure that facilitates subsequent bonding and ensures vertical electrical conduction without requiring complex surface management during assembly.
Solution Approach 2:
The patent changes physical parameters by using ion implantation to modify the surface properties of the donor substrate, creating a damaged layer that facilitates bonding. The annealing process then modifies these parameters further by repairing the crystal structure while maintaining bonding capability, enabling reliable electrical conduction.
2Strength
If surface activation bonding with argon bombardment is used to promote covalent bonds, then bonding energy is increased, but an amorphous layer is generated at the surface which negatively affects vertical electrical conduction
Solution Approach 1:
The patent converts the harmful effect of ion implantation (creating a damaged layer) into a beneficial bonding interface. The ion-damaged layer serves as an ideal bonding surface that facilitates strong adhesion, while the subsequent annealing process repairs the crystal structure to restore electrical conduction properties.
Solution Approach 2:
The patent uses ion implantation to change the physical and chemical parameters of the surface, creating a damaged layer with increased reactivity. The annealing process then changes these parameters by repairing the crystal structure, transforming the surface from a damaged state to a restored state that maintains both bonding strength and electrical conduction.
3Reliability
If dopant species implantation is used to restore electrical properties of amorphous layer, then electrical conduction is improved, but process complexity and cost increase
Solution Approach 1:
The patent extracts the need for separate dopant implantation steps by using the ion implantation process itself to create the bonding interface. The ion-damaged layer serves dual purposes: facilitating bonding and providing a pathway for electrical conduction after annealing, eliminating the need for additional dopant implantation steps.
4Reliability
If monocrystalline SiC substrates are used for microelectronics, then device performance is improved, but cost and difficulty of supply in large sizes increase
Solution Approach 1:
The patent applies segmentation by separating the monocrystalline SiC thin layer from its original thick substrate using ion implantation and annealing. This creates a standalone thin layer that can be transferred to a polycrystalline carrier substrate, enabling the use of high-performance monocrystalline material in cost-effective configurations with larger dimensions.
Solution Approach 2:
The patent uses the ion-damaged layer as an intermediary that facilitates the transfer of the monocrystalline thin layer to the polycrystalline carrier substrate. This intermediary structure enables the combination of high-performance monocrystalline material with cost-effective polycrystalline substrates, resolving the contradiction between performance and cost.
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 enables the production of high-quality composite structures with reduced defect density and improved electrical conductivity, addressing the limitations of existing methods and enhancing the performance and reliability of power devices.
Implementation Method 1
a step of ion implantation of light species into the donor layer, to form a buried brittle plane delimiting the thin layer between the buried brittle plane and a free surface of the donor layer
Implementation Method 2
a step of separation along the buried brittle plane, to form the composite structure on the one hand and the remainder of the donor substrate on the other hand
Implementation Method 3
a step of formation of a carrier substrate of silicon carbide on the free surface of the donor layer, comprising a deposition at a temperature of between 400° C. and 1100° C.
Data Source
AI summary
A method of producing a composite structure comprising a thin layer of monocrystalline silicon carbide arranged on a carrier substrate of silicon carbide comprises: a) a step of provision of an initial substrate of monocrystalline silicon carbide, b) a step of epitaxial growth of a donor layer of monocrystalline silicon carbide on the initial substrate, to form a donor substrate, c) a step of ion implantation of light species into the donor layer, to form a buried brittle plane delimiting the thin layer, d) a step of formation of a carrier substrate of silicon carbide on the free surface of the donor layer, comprising a deposition at a temperature of between 400° C. and 1100° C., e) a step of separation along the buried brittle plane, to form the composite structure and the remainder of the donor substrate, and f) a step of chemical-mechanical treatment(s) of the composite structure.