Crystalline SiC Microstructure Gap Formation via Sacrificial Layer
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Solution Overview
Problem
Existing methods for producing microstructures of crystalline SiC with gaps are hindered by the high resistance of SiC to etching chemicals and the need for intermediate layers, which compromises surface quality and temperature stability, making them unsuitable for harsh environments.
Innovation Solution
Growing a sacrificial layer of crystalline Si or GaN on a crystalline SiC substrate, allowing for high-temperature epitaxial growth and easy etching to create gaps, which enables the production of high-quality crystalline SiC microstructures suitable for harsh environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If etching of bulk crystalline SiC is used to form gaps, then gaps can be created, but the process is difficult due to high resistance to etch chemicals and requires complex selective doping layers
Solution Approach 1:
The patent applies preliminary action by growing a sacrificial layer of crystalline Si or GaN on the SiC substrate before forming the final microstructure. This sacrificial layer is deposited early in the process and is specifically designed to be easily removable, thus preparing the structure for subsequent gap formation without requiring complex etching of the final SiC material.
Solution Approach 2:
The patent uses an intermediary material (sacrificial layer of crystalline Si or GaN) that facilitates the formation of gaps. This intermediary layer is grown on the SiC substrate, allows for simple etching to create gaps, and can be completely removed afterward, leaving clean gaps in the final SiC microstructure without requiring direct etching of SiC itself.
2Ease of manufacture
If intermediate layers of another material are used for bonding substrates, then gaps can be formed between substrates, but surface quality deteriorates and temperature stability is compromised
Solution Approach 1:
The patent applies the taking out principle by completely removing the sacrificial layer after it has served its purpose. The sacrificial layer of crystalline Si or GaN is grown, used to facilitate gap formation through simple etching, and then entirely removed, leaving no intermediate material in the final structure. This extraction ensures that the final SiC microstructure maintains high surface quality and temperature stability without compromising reliability.
3Ease of manufacture
If CVD deposition of SiC onto oxide sacrificial layer is used, then microstructures can be formed, but the oxide layer becomes unstable above 1000°C resulting in inferior polycrystalline SiC quality
Solution Approach 1:
The patent applies parameter changes by selecting sacrificial layer materials (crystalline Si or GaN) that remain stable at the high temperatures required for high-quality SiC epitaxial growth. These materials can withstand temperatures above 1000°C without becoming unstable, allowing the SiC layer to be grown with superior crystalline quality while the sacrificial layer maintains its structural integrity throughout the deposition process.
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 method allows for the creation of high-quality crystalline SiC microstructures with defined gaps, suitable for microelectromechanical devices that can operate in harsh conditions, such as high temperatures and high vibrational frequencies, by overcoming the limitations of existing techniques.
Implementation Method 1
growing a sacrificial layer of crystalline Si or GaN on a crystalline SiC substrate, allowing for high-temperature epitaxial growth
Implementation Method 2
easy etching to create gaps
Data Source
Figure 1~7
AI summary
A method for producing a microstructure of crystalline SiC having at least one gap between structural parts thereof comprises the following steps: a first crystalline layer (2) of a material able to form a crystalline structure on crystalline SiC is epitaxially grown on a substrate (1) of crystalline SiC, a second layer (3) of crystalline SiC is epitaxially grown on top of the first layer, an opening (4) is made through said second layer to the first layer, and the first layer (2), thus forming a sacrificial layer, is etched away through said opening for forming a said gap between said second layer and substrate of crystalline SiC.