Multilayer IDT Electrode Structure for Spurious Wave Suppression
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Solution Overview
Problem
Existing elastic wave elements with interdigital transducer (IDT) electrodes suffer from spurious signals on the low-frequency side, which are not adequately addressed by existing thickness configurations of the IDT electrode.
Innovation Solution
The elastic wave element incorporates a first layer with a specific thickness and material, along with a second layer or a metal layer interposed between the first layer and the piezoelectric layer, satisfying specific normalized thickness and acoustic velocity relationships to reduce spurious signals on the high-frequency side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the IDT electrode thickness is increased to reduce low-frequency spurious signals, then low-frequency spurious reduction is improved, but high-frequency spurious signals are not adequately addressed and device complexity increases
Solution Approach 1:
The IDT electrode is segmented into multiple layers (first layer with thickness t1, second layer with thickness t2, and optional metal layer) with different thicknesses and materials. Each layer is optimized to address specific frequency range spurious signals, allowing simultaneous reduction of both low-frequency and high-frequency spurious without excessive overall thickness
Solution Approach 2:
Different layers of the IDT electrode are assigned different local properties (thickness, material, acoustic velocity) to address different frequency ranges. The first layer with thickness t1 addresses low-frequency spurious, while the second layer with thickness t2 addresses high-frequency spurious, creating localized optimization throughout the electrode structure
2Object-generated harmful factors
If a multi-layer electrode structure is implemented to reduce high-frequency spurious, then high-frequency spurious reduction is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes specific parameter ranges for layer thicknesses (t1 > 100 Å, t2 > 150 Å) and acoustic velocities that satisfy mathematical expressions. By defining acceptable parameter ranges rather than single precise values, the design accommodates manufacturing tolerances while still achieving spurious signal reduction
Solution Approach 2:
The electrode uses composite material structure with different layers made of different materials having different acoustic velocities. This composite approach allows the system to achieve the desired acoustic filtering effect through material selection rather than requiring extremely precise thickness control alone
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 configuration improves the characteristic of the elastic wave element by reducing spurious signals on the high-frequency side, enhancing the overall performance and efficiency of the element.
Implementation Method 1
a piezoelectric layer positioned on the supporting substrate
Implementation Method 2
an acoustic wave propagating through the piezoelectric layer
Data Source
AI summary
In an elastic wave element, an interdigital transducer electrode includes a first layer including a first material having conductivity. The first layer has a thickness greater than 100 Å. The first layer is superposed on the piezoelectric layer directly or with a metal layer of smaller than or equal to 100 Å interposed between the first layer and the piezoelectric layer. When a pitch of electrode fingers of the interdigital transducer electrode is p (μm) and a value obtained by dividing a thickness of the first layer (μm) by 2×p0.101 is a normalized thickness t1, the normalized thickness t1 and an acoustic velocity V1 (m/s) of a bulk longitudinal wave propagating through the first material satisfy an expression below:2.14×106V1-1.16×10-2<t1<1.17×10-5V1-1.63×10-2.