Acoustic Wave Layer Stack for Low IMD and High Q
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Solution Overview
Problem
Existing acoustic wave devices face challenges in sufficiently suppressing inter-modulation distortion (IMD) while maintaining a high Q value, despite the use of silicon oxide films containing hydrogen atoms as dielectric films.
Innovation Solution
The acoustic wave device incorporates a multilayer configuration with a high-acoustic-velocity material layer, a low-acoustic-velocity film made of silicon oxide with a high hydrogen atom concentration, and a piezoelectric layer, where the low-acoustic-velocity film is formed by doping dielectrics with water, effectively confining acoustic wave energy and reducing IMD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a silicon oxide film containing hydrogen atoms is used as the dielectric film, then inter-modulation distortion (IMD) is suppressed, but the Q value cannot be sufficiently maintained
Solution Approach 1:
The piezoelectric substrate is segmented into multiple functional layers: a high-acoustic-velocity supporting substrate, a low-acoustic-velocity film, and a piezoelectric film. This segmentation allows each layer to perform its specific function - the low-acoustic-velocity film suppresses IMD while the piezoelectric film concentrates acoustic wave energy to maintain high Q value.
Solution Approach 2:
The invention uses a composite multilayer structure combining materials with different acoustic velocities. The low-acoustic-velocity film (made of material including hydrogen atoms) is combined with the piezoelectric film and supporting substrate to create a composite structure that simultaneously achieves IMD suppression and high Q value.
2Reliability
If a multilayer body with high-acoustic-velocity supporting substrate and piezoelectric film is used, then Q value is high, but inter-modulation distortion (IMD) is not sufficiently suppressed
Solution Approach 1:
A low-acoustic-velocity film is introduced as an intermediary layer between the high-acoustic-velocity supporting substrate and the piezoelectric film. This intermediary layer specifically addresses IMD suppression while allowing the acoustic wave energy to remain concentrated on the piezoelectric film side for maintaining high Q value.
Solution Approach 2:
The low-acoustic-velocity film is specifically positioned between the supporting substrate and piezoelectric film where it is most needed for IMD suppression. The film's material composition (including hydrogen atoms) and acoustic velocity properties are locally optimized for this specific function without compromising the overall Q value of the device.
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 significantly reduces or prevents IMD, enhances the Q value, and minimizes frequency variations due to temperature changes, improving the overall performance of acoustic wave devices in RF front-end circuits and communication apparatuses.
Implementation Method 1
The acoustic wave device with the above-described multilayer body has a high Q value because the energy of acoustic waves is concentrated on the piezoelectric film side
Implementation Method 2
a piezoelectric layer provided on the low-acoustic-velocity film, and an interdigital transducer (IDT) electrode provided on the piezoelectric layer
Data Source
AI summary
An acoustic wave device includes a high-acoustic-velocity film, a low-acoustic-velocity film provided on the high-acoustic-velocity film, a piezoelectric layer provided on the low-acoustic-velocity film, and an IDT electrode provided on the piezoelectric layer. An acoustic velocity of bulk waves propagating through the high-acoustic-velocity film is higher than an acoustic velocity of acoustic waves propagating through the piezoelectric layer. An acoustic velocity of bulk waves propagating through the low-acoustic-velocity film is lower than an acoustic velocity of bulk waves propagating through the piezoelectric layer. The low-acoustic-velocity film includes a material including hydrogen atoms.