MEMS Guided Wave Devices with Bragg Mirror Confinement
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Solution Overview
Problem
Existing MEMS resonator devices face limitations in thermal conduction, require stringent packaging, and struggle with producing high-quality piezoelectric materials and multiple frequencies on a single substrate, particularly due to challenges with Bragg mirror reproducibility and the use of AlN piezoelectric material deposition.
Innovation Solution
The development of MEMS guided wave devices utilizing single crystal piezoelectric layers, such as lithium niobate or lithium tantalate, with guided wave confinement structures like Bragg mirrors or fast wave propagation layers, which confine laterally excited waves and enable the production of multiple resonators with different frequencies on a single substrate, improving thermal management and reducing packaging requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If AlN piezoelectric material is deposited over underlying material with different lattice structure, then deposition can be performed, but single crystal material formation is precluded and lower quality material with deviation from perfect orientation is produced
Solution Approach 1:
A buffer layer is introduced between the substrate and the piezoelectric material to serve as an intermediary that facilitates the formation of high-quality single crystal material. The buffer layer has a lattice structure that matches the substrate, allowing for proper nucleation and growth of single crystal piezoelectric material while enabling deposition on substrates with different lattice structures.
Solution Approach 2:
The buffer layer is prepared in advance before depositing the piezoelectric material. This preliminary action creates a suitable foundation with matching lattice structure, enabling subsequent single crystal growth without requiring the substrate itself to have the perfect lattice match.
2Reliability
If Bragg mirrors are used for wave confinement, then acoustic radiation dissipation is reduced, but layer thickness reproducibility is difficult to achieve consistently
Solution Approach 1:
The design of the Bragg mirror layers is optimized by carefully selecting and controlling the thickness parameters of alternating high and low acoustic impedance layers. By adjusting these parameters within specific ranges and using precise deposition techniques, consistent wave confinement is achieved while improving layer thickness reproducibility across manufacturing batches.
3Temperature
If single crystal piezoelectric layers with guided wave confinement structures are used, then thermal conduction is enhanced and packaging complexity is reduced, but device fabrication becomes more complex
Solution Approach 1:
The device employs a composite structure combining single crystal piezoelectric material with guided wave confinement structures (such as Bragg mirrors or slow wave propagation layers). This composite design enables simultaneous achievement of enhanced thermal conduction through the single crystal substrate and acoustic wave confinement through the layered structures, while the integrated fabrication process manages the overall device complexity.
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 enhances thermal conduction, reduces packaging complexity, and allows for the fabrication of high-quality piezoelectric devices with multiple resonant frequencies on a single substrate, improving the efficiency and reliability of MEMS devices.
Implementation Method 1
Piezoelectric materials acquire a charge when compressed, twisted, or distorted. This property provides a transducer effect between electrical and mechanical oscillations or vibrations.
Implementation Method 2
Confinement may be provided by reflection at a solid/air interface, or by way of an acoustic mirror (e.g., a stack of layers referred to as a Bragg mirror) capable of reflecting acoustic waves.
Implementation Method 3
an acoustic wave may be excited in a piezoelectric layer in the presence of an alternating electric signal, or propagation of an elastic wave in a piezoelectric material may lead to generation of an electrical signal.
Data Source
AI summary
A micro-electrical-mechanical system (MEMS) guided wave device includes a single crystal piezoelectric layer and at least one guided wave confinement structure configured to confine a laterally excited wave in the single crystal piezoelectric layer. A bonded interface is provided between the single crystal piezoelectric layer and at least one underlying layer. A multi-frequency device includes first and second groups of electrodes arranged on or in different thickness regions of a single crystal piezoelectric layer, with at least one guided wave confinement structure. Segments of a segmented piezoelectric layer and a segmented layer of electrodes are substantially registered in a device including at least one guided wave confinement structure.