Acoustic Wave Resonator Amorphous Layer Bulk Wave Inhibition
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Solution Overview
Problem
Existing surface acoustic wave resonators face challenges in reducing loss and spurious signals due to bulk wave excitation, despite improvements in temperature characteristics and substrate thickness configurations.
Innovation Solution
The use of a pair of comb-shaped electrodes on a piezoelectric substrate with thinner amorphous layers, where one layer is in contact with the support substrate and the other is in contact with the piezoelectric substrate, helps to reduce loss by affecting the surface acoustic wave and inhibiting bulk wave propagation, with specific thickness ratios and materials optimizing the bond strength and acoustic wave confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a piezoelectric substrate is bonded to a support substrate with an amorphous layer, then temperature characteristics are improved, but loss and spurious signals increase due to bulk wave excitation
Solution Approach 1:
The invention changes the physical state of the bonding interface by forming amorphous layers on both the support substrate and piezoelectric substrate surfaces. This parameter change in the bonding structure creates an acoustic impedance mismatch that prevents bulk wave excitation while maintaining temperature stability through the bonded configuration.
Solution Approach 2:
The invention uses composite material structure with amorphous layers composed of different materials (first amorphous layer from support substrate elements, second amorphous layer from piezoelectric substrate elements) to achieve both thermal stability and acoustic wave confinement, resolving the contradiction between temperature characteristics and loss reduction.
2Object-generated harmful factors
If the piezoelectric substrate thickness is reduced to equal or less than the acoustic wave wavelength, then spurious signals are reduced, but bond strength decreases
Solution Approach 1:
The amorphous layers act as intermediary bonding layers between the support substrate and piezoelectric substrate. These intermediary layers provide sufficient bonding strength even when the piezoelectric substrate is thin, while simultaneously preventing bulk wave excitation that causes spurious signals.
Solution Approach 2:
The invention changes the bonding mechanism from direct substrate-to-substrate bonding to bonding through amorphous intermediate layers. This parameter change in the bonding structure allows thin piezoelectric substrates to maintain adequate bond strength while achieving spurious signal reduction.
3Object-generated harmful factors
If amorphous layers are formed on both substrates, then bulk wave propagation is inhibited, but device complexity increases
Solution Approach 1:
The invention merges the bonding function and the bulk wave prevention function into a single integrated structure - the amorphous layers formed during the bonding process itself. This combining of functions achieves spurious signal reduction without proportionally increasing 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 configuration effectively reduces loss and spurious signals by optimizing the thickness and composition of the amorphous layers, improving the overall performance of the acoustic wave resonator.
Implementation Method 1
a first amorphous layer that is in contact with the support substrate and is mainly composed of one or more constituent elements of the support substrate; a second amorphous layer that is in contact with the piezoelectric substrate and the first amorphous layer
Implementation Method 2
reduce loss by affecting the surface acoustic wave and inhibiting bulk wave propagation
Implementation Method 3
a piezoelectric substrate located on the support substrate; a pair of comb-shaped electrodes that is located on an opposite surface of the piezoelectric substrate from the support substrate
Data Source
AI summary
An acoustic wave resonator includes: a support substrate; a piezoelectric substrate located on the support substrate; a first amorphous layer that is in contact with the support substrate and is mainly composed of one or more constituent elements of the support substrate; a second amorphous layer that is in contact with the piezoelectric substrate and the first amorphous layer, is mainly composed of one or more constituent elements of the piezoelectric substrate, and is thinner than the first amorphous layer; and a pair of comb-shaped electrodes that is located on an opposite surface of the piezoelectric substrate from the support substrate, each of the pair of comb-shaped electrodes including electrode fingers.