Acoustic Wave Layout With Isolated Integrated Capacitor
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Solution Overview
Problem
Conventional acoustic wave devices with integrated capacitors face issues of increased size and deterioration in characteristics due to unnecessary capacitance components affecting the IDT electrode.
Innovation Solution
The acoustic wave device incorporates a substrate with alternating high and low acoustic impedance layers, where the conductive layers in the second impedance layer form capacitors with electrodes, ensuring electrical insulation from the first impedance layer, thereby reducing size and maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a capacitor is integrally provided with the acoustic wave device, then the device size is reduced, but unnecessary capacitance components affect the IDT electrode and characteristics deteriorate
Solution Approach 1:
The acoustic wave device is divided into functionally independent regions: a first region containing the IDT electrode for acoustic wave generation, and a second region containing the capacitor for electrical function. This spatial segmentation prevents the capacitor's electric field from interfering with the IDT electrode's acoustic wave generation, thereby maintaining device characteristics while achieving size reduction through integration.
Solution Approach 2:
Different regions of the substrate are assigned different functional qualities: the first region is optimized for acoustic wave generation with IDT electrode structure, while the second region is optimized for electrical storage with capacitor structure. This local differentiation allows each component to perform its function without negative interference, resolving the contradiction between integration and performance.
2Reliability
If a discrete capacitor is used or capacitor is formed on the surface of the substrate, then capacitance function is achieved, but the device size becomes large
Solution Approach 1:
The capacitor is merged with the acoustic wave device by forming it on the same substrate in a dedicated second region. This integration eliminates the need for separate discrete capacitors, reducing overall device size while maintaining the required capacitance function. The merging is achieved through shared substrate real estate without functional interference.
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 allows for a compact acoustic wave device with improved characteristics by minimizing the impact of capacitance on the IDT electrode, achieving reduced size and enhanced functionality.
Implementation Method 1
a piezoelectric layer, an IDT electrode... The piezoelectric layer is provided on the first acoustic impedance layer and the second acoustic impedance layer. The IDT electrode is provided on the piezoelectric layer.
Implementation Method 2
an acoustic wave device using an acoustic reflection layer (acoustic impedance layer)... an acoustic reflection layer is laminated on a side of a first main surface of the piezoelectric layer
Data Source
AI summary
An acoustic wave device includes a first acoustic impedance layer and a second acoustic impedance layer, an IDT electrode, and an electrode. At least a portion of the IDT electrode overlaps the first acoustic impedance layer. At least a portion of the electrode overlaps the second acoustic impedance layer. In each of the first acoustic impedance layer and the second acoustic impedance layer, at least one of a high acoustic impedance layer and a low acoustic impedance layer is a conductive layer. A capacitor is formed by using the conductive layer of the second acoustic impedance layer and the electrode. The conductive layer in the first acoustic impedance layer is electrically insulated from the conductive layer in the second acoustic impedance layer.