AlCu Electrode Composition for Elastic Wave Device Bandwidth
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Solution Overview
Problem
Elastic wave devices with piezoelectric substrates made of lithium niobate face a trade-off between improving band width ratio and frequency-temperature characteristics, where enhancing one parameter often deteriorates the other.
Innovation Solution
Incorporating an AlCu layer with a Cu concentration of 13% or more and a higher-density metal layer, such as Mo, Cu, Ag, or Au, in the interdigital transducer electrode to reduce electrical resistance and improve both band width ratio and frequency-temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the band width ratio is improved, then the frequency-temperature characteristics deteriorate
Solution Approach 1:
The patent changes the material composition parameters of the interdigital transducer electrode by incorporating AlCu alloy with specific Cu concentration (13-37% by weight) and combining it with high-density metal layers (Mo, Cu, Ag, or Au). This parameter change in electrode composition enables simultaneous improvement of band width ratio and frequency-temperature characteristics, resolving the trade-off relationship.
Solution Approach 2:
The patent uses composite electrode structures combining AlCu alloy layers with high-density metal layers (Mo, Cu, Ag, or Au). This composite material approach allows the electrode to simultaneously achieve low electrical resistance (from AlCu), high acoustic impedance (from dense metal), and improved temperature stability, thereby resolving the contradiction between band width ratio and frequency-temperature characteristics.
2Stability of the object's composition
If the frequency-temperature characteristics are improved, then the band width ratio decreases
Solution Approach 1:
The patent modifies the electrode material parameters by using AlCu alloy with controlled Cu content (13-37% by weight) combined with high-density metals. This parameter optimization enables the electrode to provide both temperature stability and wide bandwidth, reversing the traditional trade-off where improving one parameter caused deterioration of the other.
Solution Approach 2:
The composite structure of AlCu alloy layers combined with high-density metal layers creates an electrode that simultaneously achieves improved frequency-temperature characteristics and enhanced band width ratio. The composite materials provide complementary properties that resolve the inverse relationship between these two performance parameters.
3Reliability
If a Mo layer and Al layer are stacked to enhance reflectance and reduce electrical resistance, then the frequency-temperature characteristics deteriorate when band width ratio is improved
Solution Approach 1:
The patent refines the electrode composition by specifying AlCu alloy with Cu concentration of 13-37% by weight, which optimizes the balance between electrical resistance and acoustic impedance. Combined with high-density metal layers, this compositional parameter change enables simultaneous improvement of band width ratio and frequency-temperature characteristics.
Solution Approach 2:
The patent evolves the stacked layer structure into a composite electrode system where AlCu alloy layers (providing low electrical resistance and controlled acoustic impedance) are combined with high-density metal layers (providing high acoustic impedance for reflectance). This composite structure resolves the trade-off by achieving all three requirements: low resistance, high reflectance, and temperature stability.
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 enhances the band width ratio and frequency-temperature characteristics of elastic wave devices, reducing electrical resistance and minimizing frequency variations while maintaining high corrosion resistance and ease of production.
Implementation Method 1
an elastic wave device includes a piezoelectric substrate made of lithium niobate
Implementation Method 2
an interdigital transducer electrode on the piezoelectric substrate
Implementation Method 3
a compensation layer that covers the interdigital transducer electrode, the compensation layer being made of silicon oxide and configured to compensate for frequency-temperature characteristics
Implementation Method 4
the Mo layer having a higher acoustic impedance than silicon oxide and being configured to enhance reflectance for an elastic wave
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate made of lithium niobate, an interdigital transducer electrode on the piezoelectric substrate, and a silicon oxide layer that covers the interdigital transducer electrode. The interdigital transducer electrode includes an AlCu layer and a metal layer disposed closer to the piezoelectric substrate than the AlCu layer, the metal layer having a higher density than the silicon oxide layer. The AlCu layer has a Cu concentration of about 13% or more by weight.