3C-SiC Epitaxial Substrate Separation via Vacancy Layer Formation
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Solution Overview
Problem
Existing methods for producing 3C-SiC single crystal epitaxial substrates face challenges in obtaining large-diameter free-standing substrates due to the difficulty in separating the SiC epitaxial layer from the underlying silicon substrate without causing residues or requiring high-temperature melting and additional etching steps.
Innovation Solution
A method involving a hydrogen baking step to remove natural oxide films, followed by epitaxial growth using SiC nuclei, and a diffusion step to form a vacancy layer through solid-state diffusion of Si, allowing separation of the SiC film from the silicon substrate by cooling, thus eliminating the need for high-temperature melting and etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature melting is used to separate SiC epitaxial layer from silicon substrate, then separation is achieved, but process complexity increases and residues remain
Solution Approach 1:
A buffer layer is formed between the SiC epitaxial layer and silicon substrate before epitaxial growth. This buffer layer is specifically designed to have a melting point lower than both SiC and silicon, enabling preliminary preparation for clean separation without requiring high-temperature melting of the substrate itself.
Solution Approach 2:
The buffer layer acts as an intermediary substance between the SiC epitaxial layer and silicon substrate. It facilitates easy separation by providing a intermediate layer that can be selectively removed, avoiding direct contact and contamination between SiC and silicon during separation.
2Manufacturing precision
If etching steps are added to remove residues, then separation is improved, but manufacturing time increases
Solution Approach 1:
The buffer layer's low melting point, which initially seemed like a disadvantage, is converted into a benefit. During separation, the buffer layer melts first and can be easily removed, leaving clean surfaces without requiring additional etching steps to remove residues.
Solution Approach 2:
The separation process utilizes phase transition of the buffer layer from solid to liquid state at its melting point. This phase transition enables easy removal of the buffer layer through melting and drainage, eliminating the need for chemical etching and reducing manufacturing time.
3Reliability
If bulk growth is used to increase substrate diameter, then material quality is maintained, but temperature requirements exceed 1500°C making it difficult to scale
Solution Approach 1:
The growth process is segmented into two distinct stages: bulk growth for substrate preparation at high temperature, and hetero-epitaxial growth for SiC layer formation at lower temperature. This segmentation allows each stage to operate under optimal conditions, enabling scale-up to larger diameters.
Solution Approach 2:
The invention changes the temperature parameter from bulk growth (>1500°C) to hetero-epitaxial growth (lower temperature). This parameter change enables the use of silicon substrates that can be manufactured at larger diameters, overcoming the scaling limitation of bulk growth.
4Productivity
If hetero-epitaxial growth on silicon substrate is used to increase diameter, then scalability is improved, but additional etching steps are required
Solution Approach 1:
The buffer layer is preliminarily formed before hetero-epitaxial growth, preparing the structure for easy separation. This preliminary action eliminates the need for additional etching steps after growth, maintaining high productivity while reducing process complexity.
Solution Approach 2:
The buffer layer serves as an intermediary that simplifies the separation process in hetero-epitaxial growth. Its presence allows for easy mechanical or thermal separation without requiring chemical etching, thus maintaining scalability while reducing process complexity.
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
Enables the production of large-diameter 3C-SiC free-standing substrates through a simple and efficient process, avoiding high-temperature melting and etching, and facilitating easy separation of the SiC film from the silicon substrate.
Implementation Method 1
a hydrogen baking step of annealing a single crystal silicon substrate under a hydrogen atmosphere to remove a natural oxide film on a surface of the single crystal silicon substrate
Implementation Method 2
an epitaxial step of performing a carbonization treatment on the surface of the single crystal silicon substrate after the hydrogen baking step to generate SiC nuclei
Implementation Method 3
epitaxially growing a 3C-SiC single crystal film using the generated nuclei as starting points
Implementation Method 4
a diffusion step of heating the 3C-SiC single crystal epitaxial substrate to a temperature lower than a melting point of Si under a gas atmosphere containing carbon to cause solid state diffusion of Si in the single crystal silicon substrate to an interface between the 3C-SiC single crystal film and the single crystal silicon substrate
Implementation Method 5
further growing the SiC by solid phase reaction between the diffused Si and incoming C at the interface
Implementation Method 6
by cooling, dividing is performed on the 3C-SiC single crystal epitaxial substrate along the vacancy layer
Data Source
Figure 1~3
AI summary
The present invention is a method for producing a 3C-SiC single crystal epitaxial substrate, the method including: a hydrogen baking step of annealing a single crystal silicon substrate under a hydrogen atmosphere to remove a natural oxide film on a surface of the single crystal silicon substrate; an epitaxial step of performing a carbonization treatment on the surface of the single crystal silicon substrate after the hydrogen baking step to generate SiC nuclei, and epitaxially growing a 3C-SiC single crystal film using the generated nuclei as starting points to obtain a 3C-SiC single crystal epitaxial substrate; and a diffusion step of heating the 3C-SiC single crystal epitaxial substrate to a temperature lower than a melting point of Si under a gas atmosphere containing carbon to cause solid state diffusion of Si in the single crystal silicon substrate to an interface between the 3C-SiC single crystal film and the single crystal silicon substrate, and further growing the SiC by solid phase reaction between the diffused Si and incoming C at the interface, to form a vacancy layer having vacancies generated at sites from which Si has diffused, at the interface with respect to the 3C-SiC single crystal film in the single crystal silicon substrate. Thus, the present invention provides a method for producing a 3C-SiC single crystal epitaxial substrate capable of obtaining a large-diameter 3C-SiC free-standing substrate by a simple production process.