MEMS Fabrication via Substrate Border Removal and Hydrophobic Etching

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Solution Overview

Problem

Existing methods for fabricating micro electro-mechanical systems (MEMS) structures are overly complex and time-consuming, particularly due to the complexity of removing sacrificial layers and substrates.

Innovation Solution

A method involving the use of an etchant to remove a sacrificial layer, where the substrate border portion is partially or fully removed before etching, allowing for self-limited lateral etching and creating structural layer overhangs, which limits etchant propagation and facilitates the release of target substrate portions without damaging active microstructures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If traditional methods are used to remove sacrificial layers and substrates, then complete removal is achieved, but the process becomes overly complex and time-consuming

Engineering Contradiction:

Improvefabrication speedVSAvoidprocess complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The substrate border portion is removed before the sacrificial layer etching process. This preliminary action creates a configuration where the sacrificial layer is only connected to the substrate at specific target portions, enabling selective release and simplifying the overall fabrication process by reducing the need for complex subsequent removal steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The substrate is divided into a border portion and target portions. The border portion is removed while retaining the target portions connected to the sacrificial layer. This segmentation allows differential treatment of substrate regions, enabling simplified etching processes and selective release of structural layers at specific locations

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the etchant propagates freely, then complete sacrificial layer removal is achieved, but structural layer overhangs cannot be formed and short-circuits occur

Engineering Contradiction:

Improveetching controlVSAvoiddevice reliability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The substrate is designed with different properties in different regions: the border portion is removed while target portions retain connections to the sacrificial layer. This local differentiation allows the etchant to be controlled to specific areas, enabling precise formation of structural layer overhangs at target portions while preventing short-circuits through hydrophobicity-based etchant propagation limits

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the sacrificial layer is completely removed, then no structural support remains, but structural layer overhangs cannot be formed

Engineering Contradiction:

Improvestructural layer configurationVSAvoidstructural support

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The substrate border is removed before sacrificial layer etching, creating a configuration where the sacrificial layer remains connected only at target portions. This preliminary configuration enables subsequent formation of structural layer overhangs that are supported by the remaining sacrificial layer connections, achieving both manufacturing ease and structural integrity

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

This approach simplifies the MEMS fabrication process by reducing processing time and enabling the creation of functional MEMS devices with structural layer overhangs that prevent short-circuits, resulting in efficient and reliable micro electro-mechanical systems.

Implementation Method 1

causing an etchant to remove a portion of a sacrificial layer of the MEMS structure

Methodology Applied

Scientific EffectChemical etching:

Implementation Method 2

removing the border portion of the substrate comprises causing a laser to remove the border portion of the substrate

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 3

the sacrificial layer and the substrate are hydrophobic

Methodology Applied

Scientific EffectHydrophobicity: Hydrophobe

Implementation Method 4

removal of the portion of the sacrificial layer creates a structural layer overhang resulting from etching between the structural layer and the substrate that is limited by hydrophobicity of the sacrificial layer and the substrate

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS11845654B2Methods of fabricating micro electro-mechanical systems structures

Publication Date: 2023.12.19 THE UNIV OF BRITISH COLUMBIA

AI summary

According to at least one embodiment, a method of fabricating a micro electro-mechanical systems (MEMS) structure is disclosed. The method involves causing an etchant to remove a portion of a sacrificial layer of the MEMS structure, the sacrificial layer between a structural layer of the MEMS structure and a substrate of the MEMS structure. In this embodiment, causing the etchant to remove the portion of the sacrificial layer involves causing a target portion of the substrate to be released from the MEMS structure. According to another embodiment, another method of fabricating a MEMS structure is disclosed. The method involves causing an etchant including water to remove a portion of a sacrificial layer of the MEMS structure, the sacrificial layer between a structural layer of the MEMS structure and a substrate of the MEMS structure. In this embodiment, the sacrificial layer and the substrate are hydrophobic.