PMUT Piezoelectric Barrier Layer Diffusion Control

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Solution Overview

Problem

Conventional PMUT devices face limitations in signal strength, device size, and power usage due to their complex configurations, which hinder their adoption in advanced applications such as fingerprint sensing and medical imaging.

Innovation Solution

The PMUT device incorporates a structural layer, electrical component layers, and piezoelectric layers with conductive barrier layers to prevent diffusion and enhance performance, including the use of materials like YSZ and SRO as diffusion barriers to maintain the crystalline structure and electrical integrity of the piezoelectric layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional PMUT device configurations are used, then device functionality is achieved, but signal strength is limited and power consumption is high

Engineering Contradiction:

Improvesignal strengthVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

A barrier layer is introduced as an intermediary between the piezoelectric layer and electrode layers to prevent material diffusion. This intermediary layer maintains the integrity of the piezoelectric material, thereby improving signal strength and reducing power consumption by preventing degradation mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The device employs a composite structure combining multiple materials including the piezoelectric material (PZT), barrier layer materials, and electrode materials. This composite approach allows optimization of each layer's properties to enhance overall device performance, signal strength, and energy efficiency.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If piezoelectric material is used without barrier layers, then device structure is simpler, but material diffusion occurs degrading piezoelectric properties

Engineering Contradiction:

Improvedevice structureVSAvoidpiezoelectric properties

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The barrier layer serves as a protective intermediary that prevents direct contact and diffusion between the piezoelectric material and electrode materials. This maintains the chemical composition and piezoelectric properties of the active material while adding only a thin protective layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The barrier layer is deposited in advance before any diffusion can occur, preventing the harmful interaction between piezoelectric material and electrode materials. This preliminary protective action preserves material integrity throughout the device fabrication and operation process.

Inventive Principle:

Principle #9Preliminary anti-action

3Stability of the object's composition

If barrier layers are added to prevent diffusion, then piezoelectric properties are maintained, but device fabrication becomes more complex

Engineering Contradiction:

Improvepiezoelectric propertiesVSAvoidfabrication process

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The barrier layer is deposited as a preliminary step in the fabrication process, before the piezoelectric material is applied. This preliminary action prevents diffusion issues from the outset, maintaining material integrity without requiring complex post-processing steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The barrier layer thickness and material composition are optimized to provide sufficient protection against diffusion while minimizing the impact on fabrication complexity. By carefully controlling these parameters, the device maintains piezoelectric properties with manageable 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

This configuration improves the mechanical and electrical responses of the PMUT device, reducing material diffusion and maintaining the piezoelectric properties, thus enhancing signal strength and reducing power consumption while allowing for more complex and efficient applications.

Implementation Method 1

the piezoelectric layer generates a mechanical response in response to a signal applied between the first electrode and the second electrode

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

the piezoelectric layer generates an electrical signal between the first electrode and the second electrode in response to a mechanical stress applied to the piezoelectric layer

Methodology Applied

Scientific EffectConverse piezoelectric effect: Converse Piezoelectric Effect

Implementation Method 3

the one or more barrier layers prevent diffusion of the piezoelectric layer into the first electrode and the second electrode

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Data Source

PatentUS11623246B2Piezoelectric micromachined ultrasound transducer device with piezoelectric barrier layer

Publication Date: 2023.04.11 INVENSENSE INC

AI summary

A piezoelectric micromachined ultrasound transducer (PMUT) device may include a plurality of layers including a structural layer, a piezoelectric layer, and electrode layers located on opposite sides of the piezoelectric layer. Conductive barrier layers may be located between the piezoelectric layer and the electrodes to the prevent diffusion of the piezoelectric layer into the electrode layers.