Composite Acoustic Substrate Orientation for 2f-Band Spurious Reduction

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Solution Overview

Problem

Portable terminal devices require acoustic wave elements with improved electrical characteristics and reduced signal leakage to adjacent channels, necessitating enhanced attenuation in specific frequency bands.

Innovation Solution

A composite substrate is created by bonding a piezoelectric single crystal substrate with a silicon single crystal substrate, where the silicon substrate has specific Euler angles and orientations such as (111), (110), or (100) to reduce bulk wave spurious signals in the 2f-band, thereby improving the acoustic wave element's electrical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional composite substrate is used, then the acoustic wave element can be manufactured, but bulk wave spurious signals occur in the 2f-band degrading electrical characteristics

Engineering Contradiction:

Improveelectrical characteristicsVSAvoidbulk wave spurious signals

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the crystal orientation parameters of the silicon substrate from conventional orientations to specific Euler angles (φ, θ, ψ) where ψ is offset from 0°. This parameter change in crystal orientation suppresses bulk wave spurious signals in the 2f-band while maintaining the acoustic wave element's electrical characteristics.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite substrate structure combining a piezoelectric single crystal substrate with a silicon single crystal substrate having specific Euler angles. This composite structure leverages the complementary properties of both materials to reduce spurious signals while maintaining device performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If signal attenuation in specific frequency bands is improved, then speech quality increases, but device complexity increases

Engineering Contradiction:

Improvespeech qualityVSAvoidsubstrate structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention achieves signal attenuation in specific frequency bands by changing the crystal orientation parameters (Euler angles) of the silicon substrate. This parameter change provides frequency-selective attenuation without requiring additional filtering components, thereby improving speech quality while avoiding increased device 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 approach results in acoustic wave elements with superior electrical characteristics and reduced bulk wave spurious signals, enhancing frequency stability and attenuating unwanted signals, thus improving speech quality in portable communication devices.

Implementation Method 1

a first substrate comprised of a piezoelectric single crystal

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11336254B2Composite substrate and acoustic wave element using same

Publication Date: 2022.05.17 KYOCERA CORP

AI summary

A composite substrate 10 includes a first substrate 10 comprised of a piezoelectric single crystal and a second substrate 20 comprised of a silicon single crystal bonded to the first substrate 10. In the second substrate, a planar orientation is (111), and ψ of Euler angles (φ, θ, ψ) is offset from 0°. Due to this, a bulk wave spurious is reduced in a specific frequency band.