Acoustic Device Electrode Surface Control for Piezoelectric Orientation

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Solution Overview

Problem

Conventional methods face challenges in depositing a piezoelectric layer with a desired crystallographic orientation in acoustic devices, which affects device performance.

Innovation Solution

A method involving the use of a sacrificial layer on a bottom electrode, followed by polishing and cleaning processes to maintain surface roughness, enabling precise control over the growth of a piezoelectric layer with a desired crystallographic orientation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional polishing processes are used to prepare the bottom electrode surface, then the surface becomes smooth, but the piezoelectric layer cannot achieve the desired crystallographic orientation

Engineering Contradiction:

Improvecrystallographic orientation of piezoelectric layerVSAvoidsurface preparation process complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by depositing a sacrificial layer on the bottom electrode before the final polishing step. This sacrificial layer is then selectively removed in controlled regions to create the desired surface roughness pattern before piezoelectric layer deposition, enabling the achievement of desired crystallographic orientation without requiring complex post-processing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses a sacrificial layer as an intermediary element between the bottom electrode and the piezoelectric layer. This intermediate layer facilitates the creation of controlled surface roughness features that promote desired crystallographic orientation, and is subsequently removed to leave the modified electrode surface ready for piezoelectric layer deposition

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If the surface roughness of the bottom electrode is increased to improve piezoelectric layer growth, then crystallographic orientation improves, but the surface becomes too rough for uniform deposition

Engineering Contradiction:

Improvec-axis tilt controlVSAvoidsurface uniformity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies local quality by creating regions of different surface roughness on the bottom electrode through selective sacrificial layer removal. Specific local areas are modified to have enhanced roughness to promote desired crystallographic orientation and c-axis tilt, while other areas maintain uniformity for reliable deposition, achieving both objectives simultaneously

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the surface roughness parameter of the bottom electrode in a controlled manner by adjusting the polishing conditions and sacrificial layer removal patterns. This allows optimization of the roughness parameter to achieve the desired c-axis tilt and crystallographic orientation while maintaining sufficient uniformity for reliable piezoelectric layer deposition

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 method results in improved performance of acoustic devices by ensuring the piezoelectric layer achieves a desired c-axis tilt, enhancing properties such as inductance and sensitivity.

Implementation Method 1

polishing the sacrificial layer such that a portion of the sacrificial layer remains on the bottom electrode

Methodology Applied

Scientific EffectMechanical polishing: Abrasion

Implementation Method 2

removing the remaining portion of the sacrificial layer via a cleaning process such that a surface roughness of the bottom electrode is maintained

Methodology Applied

Scientific EffectChemical cleaning:

Implementation Method 3

the subsequent growth of a piezoelectric layer on the bottom electrode can be substantially improved

Methodology Applied

Scientific EffectEpitaxial growth: Epitaxy

Data Source

PatentUS12388407B2Method for manufacturing acoustic devices with improved performance

Publication Date: 2025.08.12 QORVO US INC

AI summary

A method for manufacturing an acoustic device includes providing a substrate, providing a bottom electrode over the substrate, providing a sacrificial layer on the bottom electrode, patterning the bottom electrode and the sacrificial layer, polishing the sacrificial layer such that a portion of the sacrificial layer remains on the bottom electrode, and removing the remaining portion of the sacrificial layer via a cleaning process such that a surface roughness of the bottom electrode is maintained. By performing the polishing such that a portion of the sacrificial layer remains on the bottom electrode and subsequently removing that portion of the sacrificial layer via a cleaning process that maintains the surface roughness of the bottom electrode, the subsequent growth of a piezoelectric layer on the bottom electrode can be substantially improved.