Convex BAW Resonator Structure for Acoustic Energy Confinement

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Solution Overview

Problem

Conventional bulk acoustic wave (BAW) resonators have a low quality factor (Q) due to inefficient retention of acoustic energy, which limits their performance in modern wireless communication devices.

Innovation Solution

The development of BAW resonators with a convex surface for the piezoelectric layer, which enhances acoustic energy retention and increases the quality factor by confining main mode acoustic energy in a central portion, thereby improving system performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional flat surface design is used in BAW resonators, then the device structure is simple and easy to manufacture, but the acoustic energy retention is poor resulting in low quality factor

Engineering Contradiction:

Improvequality factorVSAvoidsurface geometry complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies curvature by forming a convex surface on the piezoelectric layer instead of using a conventional flat surface. This convex geometry confines the acoustic energy in the central portion of the resonator, reducing energy leakage at the edges and thereby increasing the quality factor by a factor of two or more while maintaining compatibility with standard manufacturing processes

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If a convex surface is introduced to confine acoustic energy, then the quality factor increases significantly, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvequality factorVSAvoidfabrication process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the geometric parameter of the piezoelectric layer surface from flat to convex by controlling the thickness profile during fabrication. This parameter change is achieved through techniques such as depositing varying thicknesses of piezoelectric material or selectively removing material, which are compatible with existing semiconductor manufacturing processes, thus improving quality factor without prohibitively increasing manufacturing complexity

Inventive Principle:

Principle #35Parameter changes

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 convex surface design increases the quality factor of BAW resonators by a factor of two or higher, leading to improved performance in wireless communication devices by reducing energy leakage and enhancing resonance response.

Implementation Method 1

electrodes (e.g., contacts, metal patches, etc.) on top and bottom surfaces of a piezoelectric layer provide voltage bias to excite acoustic waves through piezoelectric (and reverse piezoelectric) effect

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

the piezoelectric layer having a convex surface... enhances acoustic energy retention and increases the quality factor by confining main mode acoustic energy in a central portion

Methodology Applied

Scientific EffectAcoustic energy confinement: Resonance

Data Source

PatentUS20250023538A1Bulk acoustic wave resonators having convex surfaces, and methods of forming the same

Publication Date: 2025.01.16 TEXAS INSTRUMENTS INC

AI summary

In one example, an apparatus comprises an acoustic resonator, the acoustic resonator including: an electrode; and a piezoelectric layer on the electrode, in which the electrode covers entirely a surface of the piezoelectric layer, and the piezoelectric layer has a convex portion with a non-uniform thickness.