SiC Composite Structure Manufacturing via Buried Brittle Plane Separation
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Solution Overview
Problem
Existing methods for fabricating composite structures with single-crystal silicon carbide (SiC) on polycrystalline SiC substrates face challenges in achieving high electrical conductivity due to difficulties in forming a good-quality direct bond between the substrates, often resulting in the formation of an amorphous layer that impairs vertical electrical conduction, and ion implantation through thick intermediate layers is complex and costly.
Innovation Solution
A process involving a series of deposition steps at specific temperatures, including a first layer of polycrystalline SiC with high dopant concentration, ion implantation to create a buried brittle plane, and subsequent deposition of amorphous and polycrystalline SiC layers to form a carrier substrate, allowing for separation and enhancing electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct bonding is used to join single-crystal SiC and polycrystalline SiC substrates, then vertical electrical conduction can be achieved, but the bonding process is complex and costly due to the need for precise surface finish management and polytype matching
Solution Approach 1:
The patent introduces an intermediate layer of amorphous silicon carbide between the single-crystal SiC and polycrystalline SiC substrates. This intermediate layer serves as a mediator that facilitates bonding without requiring precise surface finish management or polytype matching, thereby simplifying the bonding process while maintaining vertical electrical conduction.
Solution Approach 2:
The patent changes the physical state of the intermediate layer from crystalline to amorphous, which allows for easier bonding with both single-crystal and polycrystalline substrates. The amorphous structure can accommodate different polytypes and surface conditions, reducing the complexity of the bonding process.
2Strength
If surface activation bonding with argon bombardment is used to improve bonding quality, then bonding energy increases, but an amorphous layer is generated that impairs vertical electrical conduction
Solution Approach 1:
The patent performs preliminary amorphization of the silicon carbide surface through ion implantation before bonding. This preliminary action creates a controlled amorphous layer that facilitates bonding without the need for subsequent high-energy argon bombardment, thereby avoiding the generation of harmful amorphous layers that would impair electrical conduction.
Solution Approach 2:
The patent converts the potentially harmful effect of amorphization into a beneficial one by deliberately creating a controlled amorphous intermediate layer through ion implantation. This controlled amorphous layer facilitates bonding between single-crystal and polycrystalline substrates while maintaining overall device performance, including vertical electrical conduction.
3Reliability
If ion implantation is performed through a thick intermediate layer to restore electrical properties, then electrical conductivity is improved, but the process becomes more complex and expensive
Solution Approach 1:
The patent applies local quality by creating a thin amorphous intermediate layer (a few nanometers to micrometers thick) rather than a thick layer. This thin layer allows ion implantation to effectively restore electrical properties without requiring complex high-energy implantation processes through thick materials, thereby reducing process complexity 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 achieves high electrical conductivity between the thin SiC layer and the carrier substrate with an interface resistivity lower than 5×10−5 ohm·cm2, overcoming the limitations of previous methods by simplifying the bonding process and reducing costs.
Implementation Method 1
a first step of deposition at a temperature above 1100° C. to form a first layer made of polycrystalline silicon carbide on a front side of the initial substrate
Implementation Method 2
a step of ion implantation of light species through the first layer, to form a buried brittle plane in the initial substrate
Implementation Method 3
a second step of deposition at a temperature below 900° C. to form a second layer made of amorphous and/or polycrystalline silicon carbide on the first layer
Implementation Method 4
a third step of deposition at a temperature above 1000° C. to form a third layer made of polycrystalline silicon carbide on the second layer
Data Source
AI summary
A method of fabricating a composite structure includes providing a c-SiC initial substrate, depositing a relatively thin p-SiC first layer on a front side of the initial substrate at a relatively high temperature, the first layer having a dopant concentration greater than 1019/cm3, forming a buried brittle plane in the initial substrate delineating a thin layer of single crystal SiC between the brittle plane and a front side of the initial substrate, depositing a relatively thick amorphous and/or polycrystalline SiC second layer on the first layer at a relatively low temperature, the second layer including dopants of the same type as those of the first layer, at a concentration greater than 1019/cm3, and depositing a p-SiC third layer on the second layer at a relatively high temperature. A separation along the buried brittle plane takes place during the deposition process.