Alpha-Quartz Pseudosubstrate for Homogeneous Silicon Epitaxy
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Solution Overview
Problem
Current methods cannot industrialize the integration of thin films of α-quartz epitaxially grown on silicon substrates with single crystalline orientation and controlled homogeneity, limiting their use in piezoelectric micro-electromechanical systems (MEMS) and preventing scalability beyond certain surface sizes.
Innovation Solution
A method involving a silicon (100) wafer with a thin film of α-quartz epitaxially grown, using a composition with a specific catalyst molar ratio and spin coating, followed by heat treatment, to achieve homogeneous crystallization with controlled mosaicity and scalability, suitable for larger substrate sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dip-coating technique is used to integrate α-quartz thin films on silicon substrates, then the texture, density and thickness of films can be controlled, but the films cannot be used for making piezoelectric MEMS and industrialization with single crystalline orientation and controlled homogeneity is not achieved
Solution Approach 1:
The patent changes the deposition parameters by using spin-coating instead of dip-coating, controlling the rotational speed and time to achieve uniform thin film deposition. This parameter change enables both high film homogeneity and suitability for piezoelectric MEMS applications
Solution Approach 2:
The patent utilizes phase transition from amorphous to crystalline state through controlled heat treatment. The amorphous silica layer is transformed into crystalline α-quartz by heating at 900-1100°C for 1-24 hours, achieving single crystalline orientation necessary for piezoelectric MEMS
2Productivity
If conventional methods are used to integrate α-quartz thin films, then the process can be simplified, but scalability beyond certain surface sizes is prevented
Solution Approach 1:
The spin-coating method used in the patent is a universal technique applicable to substrates of various sizes and shapes. The method can be scaled from small laboratory substrates to large industrial wafers, enabling both high precision and scalability for mass production
Solution Approach 2:
The patent applies preliminary action by first depositing an amorphous silica layer through spin-coating before performing heat treatment to crystallize it into α-quartz. This preliminary deposition step ensures uniform coverage across the entire substrate surface, which is critical for maintaining film homogeneity during subsequent scaling to larger substrates
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 enables the production of completely homogeneous α-quartz thin films on silicon wafers of various sizes, suitable for MEMS, with improved mosaicity and scalability, making them suitable for industrialization and large-scale production.
Implementation Method 1
a thin film of α-quartz (100) epitaxially grown on at least one face of the wafer
Implementation Method 2
the adaptation of the structure of α-quartz films on silicon substrates was carried out by chemical deposition in solution
Implementation Method 3
spin coating, followed by heat treatment
Implementation Method 4
followed by heat treatment, to achieve homogeneous crystallization with controlled mosaicity
Data Source
AI summary
The present invention relates to a piezoelectric, epitaxially grown pseudosubstrate comprising a silicon wafer (100) having two parallel faces, and a thin layer of α-quartz (100) grown epitaxially on one of the faces of said wafer, said thin α-quartz layer (100) exhibiting a uniform crystallization with a mosaicity around the peak (100) of the quartz of between 6° and 1° and a thickness of between 100 nm and 1 μm. The present invention also relates to a process for fabricating such a pseudosubstrate, and to the use thereof for producing piezoelectric membranes.