Guided Bulk Acoustic Wave Device With Thin Piezoelectric Layer

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Solution Overview

Problem

The manufacturing of miniaturized guided bulk acoustic wave devices for RF applications is hindered by the high cost and mechanical instability of single crystal piezoelectric substrates, particularly lithium niobate, which limits the reduction of substrate thickness below 100 μm.

Innovation Solution

A guided bulk acoustic wave device with a substrate layer and a first layer stack comprising a piezoelectric layer of thickness less than or equal to 50 μm, a first electrode layer, and a waveguide layer, utilizing thin film deposition techniques to reduce production costs and achieve a smaller volume, thereby enabling high integration density and reduced manufacturing complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If single crystal piezoelectric substrates (LiNbO3) are used to ensure mechanical stability and acoustic wave excitation, then device reliability is improved, but manufacturing cost increases and device volume cannot be reduced below 100 μm thickness

Engineering Contradiction:

Improvemechanical stabilityVSAvoidsubstrate thickness

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The device is segmented into two functional parts: a thin piezoelectric layer (≤50 μm) for acoustic wave generation and a separate substrate layer for mechanical support. This segmentation allows the piezoelectric component to be miniaturized while the substrate provides the necessary mechanical stability, resolving the contradiction between reduced volume and maintained reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from using a thick single crystal substrate (z-axis orientation) to a thin piezoelectric layer deposited on a planar substrate. This dimensional change in the piezoelectric component thickness enables volume reduction while the substrate maintains mechanical integrity, allowing devices to achieve thickness ≤50 μm without sacrificing reliability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If single crystal piezoelectric substrates are used to ensure acoustic wave excitation, then device performance is improved, but manufacturing cost increases

Engineering Contradiction:

Improveacoustic wave excitation capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention replaces expensive single crystal piezoelectric substrates with a thin piezoelectric layer deposited on a cost-effective substrate. The thin layer (≤50 μm) contains the essential piezoelectric material needed for acoustic wave excitation, while the substrate provides mechanical support at lower cost, significantly reducing manufacturing expenses.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention changes the thickness parameter of the piezoelectric component from traditional single crystal substrate thickness (≥100 μm) to a thin layer (≤50 μm). This parameter change reduces material consumption and manufacturing cost while maintaining acoustic wave excitation capability through optimized electrode structures and waveguide layers.

Inventive Principle:

Principle #35Parameter changes

3Volume of stationary object

If piezoelectric layer thickness is reduced to achieve miniaturization, then device volume is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvedevice volumeVSAvoidpiezoelectric layer thickness control

Core Design Contradiction:

Volume of stationary objectVSManufacturing precision

Solution Approach 1:

The invention employs thin film deposition techniques to create a piezoelectric layer (≤50 μm) with controlled thickness and uniform properties. The thin film approach enables precise thickness control through deposition process parameters, achieving miniaturization while maintaining manufacturing precision through established thin film fabrication methods.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The device uses a composite structure combining a thin piezoelectric layer with a substrate and waveguide layer. This composite approach distributes functional requirements across multiple layers, reducing the precision burden on any single layer while achieving overall device miniaturization. The waveguide layer and electrode structures work together to compensate for tolerances in the thin piezoelectric layer.

Inventive Principle:

Principle #40Composite materials

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 allows for the creation of miniaturized RF filters and duplexers with improved electromagnetic coupling coefficients and reduced production costs, overcoming the limitations of traditional single crystal substrates by using thinner piezoelectric layers and silicon or lithium tantalate substrates, resulting in more cost-effective and mechanically stable devices.

Implementation Method 1

a piezoelectric layer, a first electrode layer for exciting guided bulk acoustic waves

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS8283835B2Guided bulk acoustic wave device having reduced height and method for manufacturing

Publication Date: 2012.10.09 SNAPTRACK INC

AI summary

Guided bulk acoustic wave devices and method for manufacturing guided bulk acoustic wave devices are provided. A guided bulk acoustic wave device includes a resonator structure with a piezoelectric layer, an electrode layer for exciting guided bulk acoustic waves and a wave guide layer. The thickness of the piezoelectric layer is less than or equal to 50 μm.