KNN Piezoelectric Multilayer Stack With Heat-Resistant Electrode Adhesion

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Solution Overview

Problem

Conventional piezoelectric stacks with a KNN film and top electrode experience partial detachment at their boundary when heated under designated conditions.

Innovation Solution

A piezoelectric stack comprising a substrate, a piezoelectric film made of alkali niobium oxide with a perovskite structure, and a top electrode, where the top electrode is deposited after applying and removing a photoresist on the piezoelectric film, thereby reducing detachment at their boundary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional stack with piezoelectric film (KNN film) and top electrode is heated under designated conditions, then the piezoelectric functionality is maintained, but partial detachment occurs at the boundary between the KNN film and the top electrode

Engineering Contradiction:

Improveboundary adhesionVSAvoidstructural integrity under heat

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent introduces an adhesion layer as an intermediary between the KNN piezoelectric film and the top electrode. This adhesion layer acts as a mediator that improves the boundary adhesion and prevents partial detachment when the stack is heated under designated conditions, while maintaining the overall structural integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite structure consisting of multiple layers including the KNN piezoelectric film, top electrode, and adhesion layer. This composite material approach enhances the boundary adhesion between dissimilar materials (piezoelectric film and electrode) by introducing a specifically designed intermediate layer that is compatible with both materials

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

Suppresses partial detachment between the piezoelectric film and top electrode, enhancing the life and reliability of piezoelectric elements and devices, and improving manufacturing yield.

Implementation Method 1

Piezoelectric substances are widely used in functional electronic components such as sensors and actuators

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

removing the photoresist from the surface of the piezoelectric film

Methodology Applied

Scientific EffectPhotoresist removal:

Data Source

PatentEP4686371A1Piezoelectric multilayer body, piezoelectric multilayer wafer, and method for producing piezoelectric multilayer body

Publication Date: 2026.01.28 SUMITOMO CHEM CO LTD

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Figure 5(a)~5(c)

AI summary

A piezoelectric stack including: a substrate; a piezoelectric film deposited on the substrate, the piezoelectric film being constituted from an alkali niobium oxide, the alkali niobium oxide containing potassium, sodium, niobium, and oxygen and having a perovskite structure; and a top electrode deposited on the piezoelectric film, wherein in a case in which the piezoelectric stack is subjected to a heat treatment at 400 °C for 15 minutes in an atmospheric environment and then observed, no detachment having a circle equivalent diameter of 30 µm or more is observed at a boundary between the piezoelectric film and the top electrode.