Stacked Acoustic Wave Die Structure for Boundary Wave Confinement
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Solution Overview
Problem
Boundary acoustic wave devices face challenges in confining acoustic waves within the device and achieving thin, efficient designs, which affects their performance and packaging size.
Innovation Solution
A multi-layer piezoelectric device with high velocity layers on opposing sides of a piezoelectric layer and a low velocity layer between them, generating a boundary acoustic wave that is concentrated at the interface, improving wave confinement and allowing for a thinner, more compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a boundary acoustic wave device is designed without a cavity, then the package size is reduced, but the acoustic wave confinement becomes difficult
Solution Approach 1:
The patent employs a composite layered structure consisting of a piezoelectric layer, a low acoustic velocity layer, and high acoustic velocity layers. This composite material approach creates acoustic impedance mismatches that confine the boundary acoustic wave at the interface between the piezoelectric layer and low velocity layer, eliminating the need for a physical cavity while maintaining wave confinement.
Solution Approach 2:
The patent changes the acoustic velocity parameter by introducing layers with different acoustic velocities (low velocity layer between piezoelectric and high velocity layers). This parameter variation creates the conditions necessary for boundary acoustic wave confinement without requiring additional structural elements like cavities.
2Length of moving object
If the piezoelectric layer thickness is reduced, then the device becomes thinner and more compact, but the acoustic wave confinement efficiency decreases
Solution Approach 1:
The composite layered structure compensates for reduced piezoelectric layer thickness by introducing additional layers with specific acoustic velocity characteristics. The low velocity layer and high velocity layers work together to confine the acoustic wave effectively even when the piezoelectric layer is thin, maintaining confinement efficiency while enabling device thinning.
Solution Approach 2:
The patent applies local quality by creating a specific acoustic velocity profile at the interface region (low velocity layer between piezoelectric and high velocity layers). This localized structural modification enhances wave confinement at the critical interface while allowing the overall device thickness to be reduced.
3Reliability
If high velocity layers are added on opposing sides of the piezoelectric layer, then the acoustic wave confinement is improved, but the device complexity increases
Solution Approach 1:
The high velocity layers serve multiple functions: they provide acoustic wave confinement through impedance mismatch, act as protective layers, and can be integrated with existing device structures. This multi-functionality justifies the added structural elements while maintaining design efficiency.
Solution Approach 2:
The introduction of high velocity layers changes the acoustic velocity parameter distribution across the device structure. This parameter modification creates the necessary conditions for boundary acoustic wave confinement while the layers can be fabricated using existing semiconductor processing techniques, minimizing the increase in manufacturing 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
The solution effectively confines acoustic energy within the device, enabling the creation of thinner acoustic wave filters that reduce package size while maintaining performance, with improved temperature compensation and electromechanical coupling coefficients.
Implementation Method 1
A multi-layer piezoelectric device with high velocity layers on opposing sides of a piezoelectric layer and a low velocity layer between them, generating a boundary acoustic wave that is concentrated at the interface
Implementation Method 2
The acoustic wave device is configured to generate a boundary acoustic wave such that acoustic energy is concentrated at a boundary of the piezoelectric layer and the low velocity layer
Data Source
AI summary
Aspects of this disclosure relate to acoustic wave devices on stacked die. A first die can include first acoustic wave device configured to generate a boundary acoustic wave. A second die can include a second acoustic wave device configured to generate a second boundary acoustic wave, in which the second die is stacked with the first die. The first acoustic wave resonator can include a piezoelectric layer, an interdigital transducer electrode on the piezoelectric layer, and high acoustic velocity layers on opposing sides of the piezoelectric layer. The high acoustic velocity layers can each have an acoustic velocity that is greater than a velocity of the boundary acoustic wave.