Acoustic Wave Stack Structure for Delamination-Resistant High Q
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Solution Overview
Problem
Existing acoustic wave devices face issues with insufficient adhesion between the support substrate and high-acoustic-velocity film, leading to a risk of delamination.
Innovation Solution
The acoustic wave device is structured with a low-acoustic-velocity film on a support substrate, a piezoelectric layer, and a high-acoustic-velocity film between the support substrate and low-acoustic-velocity film, where the adhesion between the low-acoustic-velocity film and the support substrate is higher than that between the high-acoustic-velocity film and the support substrate, and the high-acoustic-velocity film is positioned to contact the low-acoustic-velocity film and support substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a high-acoustic-velocity film is used between the support substrate and low-acoustic-velocity film, then the Q value is improved, but adhesion between the support substrate and high-acoustic-velocity film is insufficient leading to delamination risk
Solution Approach 1:
A low-acoustic-velocity film is introduced as an intermediary layer between the high-acoustic-velocity film and the support substrate. This intermediate layer serves as a mediator that improves adhesion between the support substrate and the acoustic wave stack, preventing delamination while maintaining the high Q value achieved by the high-acoustic-velocity film.
Solution Approach 2:
The invention uses a composite structure combining materials with different acoustic velocities (high-acoustic-velocity film and low-acoustic-velocity film) in a specific arrangement. The low-acoustic-velocity film acts as an adhesion-promoting layer that interfaces well with both the support substrate and the high-acoustic-velocity film, creating a composite structure that achieves both high Q value and reliable adhesion.
2Reliability
If additional adhesive layers are added to improve adhesion, then delamination is prevented, but device complexity and manufacturing steps increase
Solution Approach 1:
The low-acoustic-velocity film performs multiple functions simultaneously: it acts as an acoustic waveguide layer, provides mechanical adhesion between the support substrate and the high-acoustic-velocity film, and contributes to the overall acoustic impedance matching. This multi-functionality eliminates the need for separate adhesive layers, reducing device complexity while maintaining reliable adhesion.
Solution Approach 2:
The low-acoustic-velocity film inherently provides adhesion functionality through its material properties and positioning in the stack, without requiring additional adhesive materials or complex bonding processes. The structure is self-sufficient, using the acoustic waveguide layer itself to provide the necessary mechanical bonding between layers.
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 enhances adhesion between layers, reducing the likelihood of delamination and maintaining the integrity of the device without requiring additional adhesive layers, while also improving electrical characteristics by reducing carrier migration and enhancing frequency-temperature characteristics.
Implementation Method 1
An acoustic velocity of a bulk wave propagating through the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric layer. An acoustic velocity of a bulk wave propagating though the high-acoustic-velocity film is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer.
Implementation Method 2
a piezoelectric layer on the low-acoustic-velocity film, an IDT electrode on the piezoelectric layer
Data Source
AI summary
An acoustic wave device includes a support substrate, a low-acoustic-velocity film on the support substrate, a piezoelectric layer on the low-acoustic-velocity film, an IDT electrode on the piezoelectric layer, and a high-acoustic-velocity film between the support substrate and the low-acoustic-velocity film. An acoustic velocity of a bulk wave propagating through the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric layer. An acoustic velocity of a bulk wave propagating though the high-acoustic-velocity film is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer. Adhesion between the low-acoustic-velocity film and the support substrate is higher than adhesion between the high-acoustic-velocity film and the support substrate. The high-acoustic-velocity film is between portions of the support substrate and the low-acoustic-velocity film, and a portion of the low-acoustic-velocity film and a portion of the support substrate contact each other.