Silicon Carbide Substrate Deposition via Dual-Temperature Buffer Layer
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Solution Overview
Problem
Conventional methods for forming silicon carbide (SiC) substrates, such as the Lely method, are costly and result in high resistivity, while using graphite substrates leads to stress/strain issues and warpage due to material mismatch and porosity, making it difficult to produce flat and crack-free SiC substrates.
Innovation Solution
A method involving a multilayer stack with a graphite substrate, a first amorphous silicon carbide buffer layer formed at specific temperatures, and a second polycrystalline silicon carbide layer, reducing stress/strain mismatch and facilitating easier removal of SiC from the substrate by preventing 'tendril' formation and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Lely method is used to form single crystalline SiC, then high purity SiC is achieved, but the production cost becomes prohibitively high and the process time becomes extremely long
Solution Approach 1:
The patent changes the deposition temperature parameter from the conventional Lely method range to a lower range (800-1000°C for the first layer, 1000-1400°C for the second layer), which enables faster deposition rates while maintaining acceptable SiC quality. This parameter change resolves the contradiction by achieving both reasonable purity and much higher productivity.
Solution Approach 2:
The patent segments the SiC deposition process into two distinct layers with different deposition conditions: a first layer at lower temperature (800-1000°C) and a second layer at higher temperature (1000-1400°C). This segmentation allows optimization of each layer for different purposes, achieving both quality and speed requirements that cannot be met by a single-step process.
2Strength
If graphite substrate is used as base substrate for SiC deposition, then mechanical strength is improved, but SiC intercolation into graphite pores causes surface roughness and makes SiC difficult to remove
Solution Approach 1:
The patent introduces an intermediary layer (first SiC layer deposited at lower temperature) between the graphite substrate and the final SiC layer. This intermediary layer prevents direct contact and intercolation between SiC and graphite pores, eliminating surface roughness issues while maintaining the mechanical strength benefits of the graphite substrate.
Solution Approach 2:
The patent performs preliminary deposition of a first SiC layer at lower temperature (800-1000°C) before depositing the final SiC layer. This preliminary action creates a barrier that prevents SiC intercolation into graphite pores, solving the surface roughness problem before the final high-quality SiC layer is formed.
3Strength
If SiC is deposited onto graphite substrate, then mechanical support is provided, but large stress/strain mismatch upon cooling causes warpage and cracks in the SiC substrate
Solution Approach 1:
The patent changes the deposition temperature parameters for the first SiC layer (800-1000°C) to be closer to the graphite substrate's thermal properties, reducing the thermal expansion mismatch. This parameter change minimizes stress/strain during cooling while maintaining structural support, resolving the contradiction between strength and stability.
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 method produces SiC substrates with reduced warpage, lower electrical resistivity, and improved surface quality, enabling the formation of flat and crack-free polycrystalline silicon carbide substrates with lower costs compared to traditional methods.
Implementation Method 1
introducing a first silicon-containing precursor to a process chamber at a first temperature of about 800° C. to less than 1,000° C. to form a first silicon carbide layer on a base substrate
Implementation Method 2
introducing a second silicon-containing precursor, that is the same or different than the first silicon-containing precursor, to the process chamber at a second temperature of about 1,000° C. to about 1,400° C. to form a second silicon carbide layer on the first silicon carbide layer
Data Source
AI summary
Embodiments of the present disclosure generally relate to silicon carbide coated base substrates, silicon carbide substrates thereof, and methods for forming silicon carbide coated base substrates. In some embodiments, a method includes introducing a first silicon-containing precursor to a process chamber at a first temperature of about 800° C. to less than 1,000° C. to form a first silicon carbide layer on a base substrate. The method includes introducing a second silicon-containing precursor, that is the same or different than the first silicon-containing precursor, to the process chamber at a second temperature of about 1,000° C. to about 1,400° C. to form a second silicon carbide layer on the first silicon carbide layer.