MEMS Cavity Sealing via Atmospheric PECVD

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Solution Overview

Problem

Conventional methods for sealing openings in microelectromechanical systems (MEMS) fail to maintain a well-defined internal atmosphere and fluid composition, as sealing materials and their components can penetrate into the cavity, causing damage and influencing mechanical properties.

Innovation Solution

A method involving a substrate with a cavity where a specific fluid composition and pressure are introduced, and a sealing material is applied using a plasma-enhanced chemical vapor deposition process at atmospheric pressure, forming at the opening site to prevent penetration and allowing for controlled sealing, with optional use of a paste or liquid sealing material and anti-stiction coating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sealing material is applied directly to close openings in the substrate, then the openings are sealed and fluid is enclosed in the cavity, but sealing material and its components penetrate into the cavity causing damage to mechanical structures

Engineering Contradiction:

Improveintegrity of mechanical structuresVSAvoidpenetration of sealing material into cavity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A protective coating is applied to the inner surfaces of the cavity before the sealing material is applied to the openings. This preliminary protective layer prevents the sealing material from penetrating into and damaging the mechanical structures during the sealing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective coating acts as an intermediary barrier between the sealing material and the mechanical structures. It allows the sealing material to be applied to close the openings while preventing direct contact and damage to the sensitive mechanical components inside the cavity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If conventional sealing methods are used to close openings, then the cavity is sealed, but the fluid pressure and composition cannot be well-defined and are influenced by sealing process conditions

Engineering Contradiction:

Improvefluid compositionVSAvoiddecoupling from sealing process

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The cavity is filled with the desired fluid and the protective coating is applied before the sealing material is applied to close the openings. This preliminary filling allows the fluid to be introduced under controlled conditions, and the subsequent sealing process occurs at atmospheric pressure without affecting the fluid's pressure or composition.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The conventional sequence is inverted: instead of sealing the cavity first and then filling it with fluid under pressure, the fluid is introduced first under controlled conditions, and then the sealing is performed at atmospheric pressure. This inversion allows independent control of fluid properties separate from the sealing process conditions.

Inventive Principle:

Principle #13The other way round (Inversion)

3Object-affected harmful factors

If sealing material is applied at atmospheric pressure, then penetration into the cavity is prevented, but the mechanical properties of structures in the cavity are influenced

Engineering Contradiction:

Improvepenetration preventionVSAvoidmechanical properties

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The sealing process is performed at atmospheric pressure rather than under vacuum or elevated pressure conditions. This parameter change prevents the sealing material from penetrating into the cavity while the protective coating mitigates any adverse effects of atmospheric pressure on the mechanical structures during the sealing process.

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 method effectively seals the cavity with a well-defined fluid composition and pressure, decoupling it from ambient conditions, preventing damage and enhancing mechanical properties by controlling pressure and composition, thus improving the reliability and performance of integrated components.

Implementation Method 1

the sealing material is formed by a plasma-enhanced chemical vapor deposition process under an atmospheric pressure (PECVD)

Methodology Applied

Scientific EffectPlasma-enhanced chemical vapor deposition: Plasma Enhanced Chemical Vapour Deposition

Implementation Method 2

In a chemical vapor deposition process, the sealing material is initially brought in the form of components to the location of the deposition, in order to form the sealing material in the same place by a chemical and/or physical transformation

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Implementation Method 3

carrying out the chemical vapor deposition according to the present invention at atmospheric pressure advantageously prevents the diffusion of harmful substances through the opening into the cavity

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS8304845B2Method for sealing an opening

Publication Date: 2012.11.06 ROBERT BOSCH GMBH

AI summary

An integrated component having a substrate, the substrate having a cavity which surrounds a mechanical structure. The cavity is filled by a fluid of a specific composition under a specific pressure, and the mechanical properties of the mechanical structure are influenced by the fluid.