Composite Electrode Acoustic Wave Filter for Low Insertion Loss
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Solution Overview
Problem
Existing acoustic wave elements and their formation methods are not fully satisfactory for meeting the evolving requirements of wireless communication devices, particularly in terms of bandwidth and frequency, as they fail to optimize acoustic and electrical impedance for efficient signal filtering.
Innovation Solution
The acoustic wave element features a composite electrode structure with a layer of higher acoustic impedance adjacent to the piezoelectric layer and a layer of lower electrical impedance away from it, along with a cavity design that exposes the lower surface of the electrode, enhancing acoustic wave reflection and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-layer electrode is used, then the device structure is simple, but the acoustic impedance and electrical impedance cannot be optimized simultaneously
Solution Approach 1:
The electrode is divided into multiple layers, each with different material compositions and impedance characteristics. The first layer has high acoustic impedance while the second layer has low electrical impedance, allowing independent optimization of acoustic and electrical properties without compromising the other.
Solution Approach 2:
The patent employs composite electrode structure using different materials for each layer. The first layer uses material with high acoustic impedance (such as tungsten or molybdenum) while the second layer uses material with low electrical impedance (such as aluminum or copper), creating a composite structure that achieves both acoustic wave reflection and electrical conductivity optimization.
2Loss of energy
If the acoustic impedance of the electrode is increased to improve acoustic wave reflection, then the electrical impedance also increases, reducing electrical conductivity
Solution Approach 1:
The electrode is segmented into two functional layers: the first layer (adjacent to piezoelectric layer) uses high acoustic impedance material for acoustic wave reflection, while the second layer (away from piezoelectric layer) uses low electrical impedance material for electrical conductivity, thus resolving the impedance conflict.
Solution Approach 2:
Different regions of the electrode have different material properties optimized for their specific functions. The first layer near the piezoelectric interface is optimized for acoustic impedance matching and reflection, while the second layer is optimized for electrical conductivity, allowing local optimization of properties.
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 improves the resonance efficiency and reduces insertion loss, resulting in better filter performance by effectively reflecting acoustic waves and maintaining high electrical conductivity.
Implementation Method 1
a piezoelectric layer on the first electrode
Implementation Method 2
the first layer has a first acoustic impedance and a first electrical impedance, the second layer has a second acoustic impedance and a second electrical impedance, wherein the first acoustic impedance is higher than the second acoustic impedance
Data Source
AI summary
An acoustic wave element includes: a substrate; a bonding structure on the substrate; a support layer on the bonding structure; a first electrode including a lower surface on the support layer; a cavity positioned between the support layer and the first electrode and exposing a lower surface of the first electrode; a piezoelectric layer on the first electrode; and a second electrode on the piezoelectric layer, wherein at least one of the first electrode and the second electrode includes a first layer and a second layer that the first layer has a first acoustic impedance and a first electrical impedance, the second layer has a second acoustic impedance and a second electrical impedance, wherein the first acoustic impedance is higher than the second acoustic impedance, and the second electrical impedance is lower than the first electrical impedance.