Piezoelectric Element With ZrO2 Diffusion Layer

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Solution Overview

Problem

KNN-based piezoelectric elements often experience cracks at boundary surfaces, leading to potential leakage currents and damage due to foreign matter ingress, particularly when using ZrO2 as a diffusion inhibition layer, which results in reduced resistance to external pressures and vibrations.

Innovation Solution

A piezoelectric element design incorporating a silicon substrate with a first diffusion inhibition layer made of zirconium oxide between the substrate and the piezoelectric layer, ensuring continuous formation of the piezoelectric layer across the electrode and substrate surfaces to reduce thermal expansion coefficient differences and prevent crack formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a diffusion inhibition layer made of ZrO2 is used between the substrate and piezoelectric layer, then element diffusion is inhibited, but cracks occur at boundary surfaces and resistance to external pressures and vibrations is reduced

Engineering Contradiction:

Improvecrack resistanceVSAvoidresistance to external pressures and vibrations

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent uses a composite structure consisting of a silicon substrate, a ZrO2 diffusion inhibition layer, and a KNN-based piezoelectric layer. This composite material approach allows each layer to perform its specific function: the silicon substrate provides mechanical strength and thermal stability, the ZrO2 layer prevents element diffusion, and the KNN layer provides piezoelectric functionality, thereby resolving the contradiction between crack resistance and resistance to external pressures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the thickness parameters of each layer to resolve the contradiction. Specifically, the ZrO2 diffusion inhibition layer is controlled within a thickness range of 1 nm to 100 nm, which is sufficient to prevent element diffusion while maintaining flexibility and resistance to external pressures and vibrations, thereby preventing crack formation at boundary surfaces.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the piezoelectric layer is continuously formed across electrode and substrate surfaces, then thermal expansion coefficient differences are reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvethermal expansion compatibilityVSAvoidcontinuous layer formation precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent employs a continuous piezoelectric layer formation process that ensures homogeneous coverage across the electrode and substrate surfaces. This continuous layer structure eliminates voids and discontinuities, thereby reducing the impact of thermal expansion coefficient differences between materials and improving reliability without requiring excessive manufacturing precision.

Inventive Principle:

Principle #33Homogeneity

Solution Approach 2:

The patent performs preliminary surface preparation and diffusion inhibition layer formation before depositing the piezoelectric layer. This preliminary action ensures that the substrate surface is properly prepared and protected, facilitating subsequent continuous piezoelectric layer formation with reduced manufacturing precision requirements.

Inventive Principle:

Principle #10Preliminary action

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 use of a silicon substrate with a zirconium oxide diffusion inhibition layer effectively reduces crack occurrence and element diffusion, enhancing the piezoelectric element's durability and reliability by minimizing thermal expansion coefficient differences and preventing foreign matter ingress.

Implementation Method 1

a first diffusion inhibition layer containing an insulating material is disposed between the substrate and the piezoelectric layer

Methodology Applied

Scientific EffectDiffusion inhibition: Diffusion Barrier

Implementation Method 2

a piezoelectric layer formed on the first electrode and containing potassium, sodium, and niobium

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20230320218A1Piezoelectric element and piezoelectric element application device

Publication Date: 2023.10.05 SEIKO EPSON CORP

AI summary

A piezoelectric element according to the present disclosure includes: a substrate containing silicon; a first electrode formed on the substrate; a piezoelectric layer formed on the first electrode and containing potassium, sodium, and niobium; and a second electrode formed on the piezoelectric layer, in which a first diffusion inhibition layer containing an insulating material is disposed between the substrate and the piezoelectric layer, the piezoelectric layer is continuously formed on a first region which is a surface of the first electrode, a second region which is a surface of the first diffusion inhibition layer, and a third region which is a surface of the substrate, and the third region is between the first region and the second region.