Piezoelectric MEMS Layer Transfer for Electrode-Safe Resonators
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Solution Overview
Problem
Current methods for producing micro-electro-mechanical components with piezoelectric layers face challenges such as degradation of lower electrodes, complexity in achieving specific crystalline orientations, and difficulties in scaling up due to high-temperature processing and chemical reactivity, which limit the efficiency and compactness of filters and resonators.
Innovation Solution
A method involving epitaxial growth of piezoelectric layers, followed by thermal annealing and chemical etching to detach temporary substrates, allowing for the production of micro-electro-mechanical systems with piezoelectric materials like LiNbO3 or LiTaO3 without degrading lower electrodes, and enabling flexible crystalline orientations and scalable production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-based piezoelectric materials (PZT) are used to achieve strong piezoelectric properties, then the piezoelectric performance is improved, but environmental toxicity and manufacturing restrictions increase
Solution Approach 1:
The patent changes the material composition parameters by replacing lead-based PZT with lead-free alternatives such as lithium niobate, lithium tantalate, potassium niobate, barium titanate, and bismuth sodium titanate. This substitution maintains piezoelectric functionality while eliminating environmental toxicity associated with lead materials
Solution Approach 2:
The patent employs composite material strategies by combining piezoelectric layers with specific substrate materials and structural configurations. The use of monocrystalline or epitaxied piezoelectric layers on suitable substrates creates composite structures that achieve high electromechanical coupling coefficients without relying on toxic lead-based materials
2Reliability
If PZT material is used for low-frequency applications, then strong piezoelectric properties are achieved, but electrical and mechanical losses become unacceptable for high-frequency applications
Solution Approach 1:
The patent changes the material selection to lead-free piezoelectric materials such as lithium niobate, lithium tantalate, and their solid solutions, which exhibit lower electrical and mechanical losses at high frequencies compared to PZT, while maintaining adequate piezoelectric properties for both low and high-frequency applications
3Reliability
If PZT material is used to achieve strong piezoelectric properties, then the piezoelectric performance is improved, but the material loses its piezoelectric properties at high temperature
Solution Approach 1:
The patent selects piezoelectric materials with higher Curie temperatures and better thermal stability, such as lithium niobate, lithium tantalate, and barium titanate-based compositions. These materials maintain their piezoelectric properties at elevated temperatures where PZT would lose its functionality
4Reliability
If monocrystalline lithium niobate layers are grown to achieve high electromechanical coupling coefficients, then the piezoelectric performance is improved, but the manufacturing complexity and difficulty of integration increase
Solution Approach 1:
The patent performs preliminary actions by preparing substrates with specific crystallographic orientations and surface treatments before epitaxial growth. This pre-preparation ensures that the lithium niobate or lithium tantalate layers grow with the desired crystalline orientation and high quality, simplifying subsequent processing steps
Solution Approach 2:
The patent uses intermediary buffer layers or transition layers between the substrate and the piezoelectric layer. These intermediary layers facilitate the epitaxial growth process, improve lattice matching, and reduce defect formation, thereby simplifying the overall manufacturing process while maintaining high electromechanical coupling coefficients
5Volume of moving object
If thin piezoelectric layers are deposited to enable MEMS miniaturization, then the device size is reduced, but the available material choices are limited to a few polycrystalline materials
Solution Approach 1:
The patent changes the deposition technique from conventional polycrystalline deposition to epitaxial growth methods. This parameter change enables the formation of thin monocrystalline or highly oriented piezoelectric layers, expanding material choices to include lithium niobate, lithium tantalate, potassium niobate, and their solid solutions, while maintaining the thin-film format required for MEMS applications
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 enables the production of high-quality micro-electro-mechanical components with improved piezoelectric coupling coefficients, enhanced manufacturing efficiency, and compactness, suitable for high-frequency applications without the limitations of existing techniques.
Implementation Method 1
Piezoelectricity, discovered in 1880 by the Curie brothers (P. Curie, Notice sur les travaux scientifiques de MP Curie, Gauthier-Villars (1902)) is the capacity of a crystal to polarize under the action of a mechanical constraint, or conversely to deform under the action of an electrical voltage. Piezoelectric materials therefore make it possible to ensure electromechanical, or mechano-electrical, transduction.
Implementation Method 2
A method involving epitaxial growth of piezoelectric layers, followed by thermal annealing and chemical etching to detach temporary substrates
Implementation Method 3
A method involving epitaxial growth of piezoelectric layers, followed by thermal annealing and chemical etching to detach temporary substrates
Implementation Method 4
A method involving epitaxial growth of piezoelectric layers, followed by thermal annealing and chemical etching to detach temporary substrates
Data Source
Figure 1a~1d
Figure 1e~1g
Figure 1h~1j
AI summary
The invention relates to a method for manufacturing a micro-electromechanical system comprising the following steps: - creating a stack on the surface of a temporary substrate (100) so as to create a first assembly comprising: - at least the deposition of a piezoelectric material or a ferroelectric material to create a layer of piezoelectric material (300); - creating a first bonding layer (500b); - creating a second assembly comprising at least the creation of a second bonding layer (500c) on the surface of a host substrate (700); - creating at least one acoustic insulation structure in at least one of the two assemblies; - creating at least one electrode level(s) in at least one of the two assemblies; - bonding said two assemblies via said two bonding layers before or after creating at least one electrode level(s) in at least one of the two assemblies;- the removal of said temporary substrate.;