MEMS Piezoelectric Micro Speaker Fabrication

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing micro speaker technologies, particularly piezoelectric types, face challenges in miniaturization and cost reduction while maintaining performance, and require additional packaging processes that increase complexity and cost.

Innovation Solution

A micro speaker structure and fabrication method using batch processing to form a package wafer and device wafer, bonded with a eutectic bond or polymer adhesion, and employing xenon difluoride (XeF2) for isotropic etching to create a diaphragm, simplifying the process and reducing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional packaging processes are used to protect the active surface and back surface, then reliability is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improveprotection of active surface and back surfaceVSAvoidpackaging process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the package substrate and device substrate into a single integrated structure. The package substrate serves dual functions as both the device substrate and the protective package, eliminating the need for separate packaging processes while maintaining protection of the active surface and back surface.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The package substrate is designed to perform multiple functions simultaneously: it serves as the device substrate for mounting piezoelectric elements, provides structural support, and acts as the protective package. This multi-functionality reduces the number of separate components and processes needed.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If traditional vapor-deposition bonding is used for substrate assembly, then manufacturing precision is maintained, but productivity decreases due to sequential processing

Engineering Contradiction:

Improvesubstrate bonding precisionVSAvoidbatch processing efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent prepares multiple substrates in advance with pre-formed cavities, electrodes, and other structures before bonding. This preliminary preparation allows for batch processing of multiple devices simultaneously while maintaining precision through controlled deposition and etching processes performed on entire wafer batches rather than individual devices.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If batch processing is used to form package wafer and device wafer, then productivity is improved, but manufacturing precision may be compromised

Engineering Contradiction:

Improvebatch processing efficiencyVSAvoidbonding and etching precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies different processing conditions to different regions of the batch substrates. For example, selective etching is performed on specific areas to form cavities and vent holes, while other regions receive different treatments. This allows batch processing to maintain precision by tailoring the process to local requirements rather than applying uniform treatment to all substrates.

Inventive Principle:

Principle #3Local quality

4Ease of manufacture

If isotropic etching with XeF2 is used to form diaphragm, then ease of manufacture is improved, but control over diaphragm shape becomes more difficult

Engineering Contradiction:

Improvediaphragm formation simplicityVSAvoiddiaphragm shape control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent forms a protective layer with a pre-defined pattern before performing the isotropic etching. This protective layer acts as a mask that guides the etching process, allowing the simple isotropic etching to produce precisely controlled diaphragm shapes by limiting the etching to specific regions defined by the mask pattern.

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 method enables cost-effective, compact, and lightweight micro speakers with reduced thermal deformation issues, while maintaining performance and simplifying the fabrication process.

Implementation Method 1

forming a diaphragm by isotropic-etching a back surface of the device wafer using a xenon difluoride (XeF2)

Methodology Applied

Scientific EffectIsotropic etching:

Implementation Method 2

forming a first metal along a surface of the back cavity by vapor-deposition; forming an electrode by vapor depositing with a second metal

Methodology Applied

Scientific EffectVapor deposition: Physical Vapour Deposition

Data Source

PatentUS8275155B2Method for fabricating micro speaker and micro speaker fabricated by the same

Publication Date: 2012.09.25 SAMSUNG ELECTRONICS CO LTD

AI summary

A method for fabricating a micro speaker is provided, including forming a package wafer and a device wafer by batch processing, bonding the package wafer and the device wafer to each other, and forming a diaphragm by isotropic-etching a back surface of the device wafer using a xenon difluoride (XeF2). As a result, a micro-electronic-mechanic system (MEMS) technology-based piezoelectric micro speaker having a wide frequency response range is realized, by batch processing, thereby providing simplified structure and processing and reducing fabricating cost.