Assembly with partially embedded interdigital transducer electrode

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Solution Overview

Problem

Existing acoustic wave filters face challenges in achieving high frequency resonance and power durability, particularly in laterally excited bulk acoustic wave resonators, due to heat dissipation and mechanical ruggedness issues, especially in high-frequency applications like 5G NR bands.

Innovation Solution

A stacked acoustic wave device assembly is introduced, featuring a laterally excited bulk acoustic wave resonator with a solid acoustic mirror between the piezoelectric layer and a support substrate, and a stacked structure that includes a silicon support substrate with high thermal conductivity to enhance heat dissipation and mechanical ruggedness, while maintaining high frequency resonance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a laterally excited bulk acoustic wave resonator is used for high-frequency applications, then high frequency resonance is achieved, but heat dissipation and mechanical ruggedness deteriorate

Engineering Contradiction:

ImprovefrequencyVSAvoidpower durability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent transitions from a planar surface acoustic wave structure to a three-dimensional bulk acoustic wave structure by embedding the interdigital transducer electrode within the piezoelectric layer and adding a bottom electrode on the opposite side. This dimensional change enables bulk wave propagation modes that support higher frequencies while providing better thermal pathways through the substrate, thereby resolving the contradiction between high-frequency operation and power durability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent employs a composite structure consisting of multiple layers including piezoelectric material, metal electrodes, and substrate materials with different thermal and mechanical properties. This composite approach allows optimization of each layer for specific functions: the piezoelectric layer for high-frequency resonance, the metal electrodes for electrical conduction, and the substrate for heat dissipation and mechanical support, thus achieving both high frequency and power durability.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the interdigital transducer electrode is completely embedded in the piezoelectric layer, then acoustic energy confinement is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveacoustic energy confinementVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent divides the electrode structure into distinct segments: a top interdigital transducer electrode partially embedded in the piezoelectric layer, a bottom electrode on the opposite side, and interdigitated fingers. This segmentation allows each component to be optimized independently for acoustic confinement while simplifying the manufacturing process by enabling separate fabrication and assembly steps, thus resolving the contradiction between acoustic energy confinement and manufacturing ease.

Inventive Principle:

Principle #1Segmentation

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 confines acoustic energy and improves thermal dissipation and mechanical durability, enabling high-frequency operation with desirable power durability in 5G NR and other high-frequency applications.

Implementation Method 1

a solid acoustic mirror between the piezoelectric layer and a support substrate

Methodology Applied

Scientific EffectAcoustic reflection: Reflection

Implementation Method 2

a stacked structure that includes a silicon support substrate with high thermal conductivity to enhance heat dissipation

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

a first interdigital transducer electrode in contact with the first piezoelectric layer. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20230107820A1Assembly with partially embedded interdigital transducer electrode

Publication Date: 2023.04.06 SKYWORKS SOLUTIONS INC

AI summary

An acoustic wave device assembly is disclosed. The acoustic wave device assembly can include a first acoustic wave device that includes a first substrate, a first piezoelectric layer, a first solid acoustic mirror that is disposed between the first substrate and the first piezoelectric layer, and a first interdigital transducer electrode that has a first portion embedded in the first piezoelectric layer and a second portion disposed over a surface of the first piezoelectric layer. The acoustic wave device assembly can include a second acoustic wave device that includes a second substrate, a second piezoelectric layer, a second solid acoustic mirror that is disposed between the second substrate and the second piezoelectric layer, and a second interdigital transducer electrode that is in contact with the second piezoelectric layer. The second acoustic wave device is stacked over the first acoustic wave device. The first acoustic wave device and the second acoustic wave device are spaced by a spacer assembly such that a cavity is formed between the first acoustic wave device and the second acoustic wave device.