SAW Resonator Passivation Layout for SH Spur Suppression

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Solution Overview

Problem

Existing surface acoustic wave (SAW) devices with multiple resonators of different types face challenges in optimizing the piezoelectric cut angle and temperature compensation layer thickness to effectively suppress shear horizontal (SH) spurs, which interfere with desired signals and degrade performance.

Innovation Solution

The SAW device incorporates a piezoelectric layer with varying cut angles and a passivation layer with distinct thicknesses over different resonators, along with a temperature compensation layer, to selectively suppress SH spurs by adjusting the thickness and material properties to enhance signal filtering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a single piezoelectric cut angle is used for all resonators, then the device structure is simple, but SH spurs cannot be effectively suppressed

Engineering Contradiction:

ImproveSH spur suppressionVSAvoiddevice structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies local quality by assigning different piezoelectric cut angles to different resonators based on their specific functions. The first resonator uses a first cut angle optimized for its operation, while the second resonator uses a second cut angle optimized for its operation, allowing each resonator to independently suppress SH spurs without compromising the other's performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the piezoelectric substrate into multiple regions with different cut angles. This segmentation allows each resonator to be positioned on an optimally oriented substrate region, enabling independent optimization of SH spur suppression for each resonator type while maintaining overall device functionality.

Inventive Principle:

Principle #1Segmentation

2Reliability

If uniform passivation layer thickness is used, then manufacturing is simpler, but resonator performance optimization is limited

Engineering Contradiction:

Improveresonator performanceVSAvoidpassivation layer thickness control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent implements local quality through a passivation layer with spatially varying thickness. The passivation layer is thicker over the first resonator and thinner over the second resonator, allowing each resonator to operate under its optimal mechanical and electrical conditions, thereby improving overall device reliability and performance.

Inventive Principle:

Principle #3Local quality

3Temperature

If temperature compensation layer thickness is increased, then temperature stability improves, but SH spur suppression may be compromised

Engineering Contradiction:

Improvetemperature stabilityVSAvoidSH spur interference

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by positioning the temperature compensation layer selectively over specific resonators based on their temperature sensitivity requirements. This allows temperature-stable resonators to have thinner or absent compensation layers (reducing SH spurs), while temperature-sensitive resonators receive thicker compensation layers for stability, optimizing both temperature performance and spur suppression.

Inventive Principle:

Principle #3Local quality

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 effectively suppresses SH spurs, improving the performance of SAW devices by reducing interference and enhancing signal quality.

Implementation Method 1

A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. 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

Implementation Method 2

a temperature compensation layer between the piezoelectric layer and the passivation layer

Methodology Applied

Scientific EffectTemperature compensation: Thermal Expansion

Data Source

PatentUS20250330140A1Shear horizontal mode spur suppression for temperature compensated surface acoustic wave devices

Publication Date: 2025.10.23 SKYWORKS SOLUTIONS INC

AI summary

A surface acoustic wave device and a method of forming the surface acoustic wave device are disclosed. A Rayleigh mode is a main mode in the surface acoustic wave device. The surface acoustic wave device can include a piezoelectric layer, a first resonator and a second resonator in electrical communication with the piezoelectric layer, and a passivation layer. The first resonator has a different resonator type from the second resonator. The passivation layer has a first thickness over the first resonator and a second thickness over the second resonator. The first thickness is different from the second thickness.