SiC Substrate Carbonization Residual Silicon Interface
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Solution Overview
Problem
Existing methods for manufacturing nitrogen compound semiconductor substrates and single crystal SiC substrates face issues with crystal defects and waviness at the interface, leading to degraded crystallinity and increased costs due to the need for expensive ion implantation processes.
Innovation Solution
A method involving the conversion of a surface Si layer on an SOI substrate to a single crystal SiC layer with a residual Si layer at the interface, followed by epitaxial growth of nitrogen compound semiconductor layers, which improves the flatness and crystallinity of the SiC layer and reduces waviness without relying on ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface Si layer is completely converted to SiC layer, then the crystallinity of SiC layer is improved, but the interface flatness deteriorates due to waviness formation
Solution Approach 1:
The patent applies preliminary action by forming a buffer layer of Si-SiC mixed crystal at the interface before complete SiC conversion. This buffer layer is created during the carbonization process by controlling the conversion depth, leaving a transitional region that prevents interface waviness while maintaining SiC layer crystallinity. The buffer layer acts as a pre-prepared intermediate structure that resolves the conflict between complete conversion and interface flatness.
2Shape
If ion implantation is used to improve interface flatness, then the interface waviness is reduced, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for ion implantation process by using a purely thermal carbonization method. The extraneous ion implantation step is removed from the manufacturing process, replacing it with a simplified thermal treatment that achieves the same interface flatness improvement through controlled SiC formation and buffer layer creation, thereby reducing manufacturing complexity and cost.
Solution Approach 2:
The patent substitutes the mechanical/physical ion implantation process with a thermal chemical process. Instead of using ion beams to modify the interface, the patent uses thermal carbonization in a carbon-containing atmosphere to naturally form the buffer layer and improve interface flatness, replacing a complex physical process with a simpler thermal-chemical process.
3Ease of manufacture
If the surface Si layer is thinned to approximately 10 nm, then the carbonization process is simplified, but the interface stability deteriorates due to rapid Si→SiC reaction
Solution Approach 1:
The patent applies parameter changes by optimizing the Si layer thickness to a specific range (5-20 nm) and controlling the carbonization temperature and atmosphere composition. By adjusting these parameters, the patent achieves a balance where the Si layer is thin enough for simplified processing but thick enough to maintain interface stability during the Si→SiC conversion, preventing excessive reaction rates that would cause interface degradation.
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 results in high-quality nitrogen compound semiconductor substrates with improved crystallinity and reduced manufacturing costs, as the residual Si layer enhances the flatness and stability of the SiC interface, leading to better semiconductor performance.
Implementation Method 1
heating it for a predetermined period of time in a heating furnace under a mixture gas atmosphere of hydrogen gas and hydrocarbon-series gas, the surface silicon layer is carbonized at a high temperature to convert into a single crystal SiC thin film
Implementation Method 2
by an epitaxial method using the single crystal SiC thin film as a seed layer, an SiC layer can be grown thereon
Data Source
AI summary
In order to provide a method for manufacturing a single crystal SiC substrate that can obtain an SiC layer with good crystallinity, an Si substrate 1 having a surface Si layer 3 of a predetermined thickness and an embedded insulating layer 4 is prepared, and when the Si substrate 1 is heated in a carbon-series gas atmosphere to convert the surface Si layer 3 into a single crystal SiC layer 6, the Si layer in the vicinity of an interface 8 with the embedded insulating layer 4 is left as a residual Si layer 5.