MEMS Micro-Mirror Support Structure for Reduced Deformation

Solution Overview

Problem

The design and fabrication of fast micro mirrors for personal projectors face challenges in achieving large tilting angles and resonance frequencies while minimizing dynamic deformations, which are exacerbated by the need to reduce mirror mass, leading to inaccuracies and performance limitations in existing support structure methods.

Innovation Solution

The use of silicon-on-insulator (SOI) or double active layer silicon-on-insulator (DSoI) technology to fabricate MEMS scanning micro-mirror devices with support structures patterned from the second silicon layer, ensuring lightweight and rigid structures through precise etching of the full thickness of the second layer, forming shapes like a cross surrounded by a ring, and using oxide layers for separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the mirror mass is reduced by thinning the mirror, then the resonance frequency and tilting angle are improved, but dynamic deformations increase

Engineering Contradiction:

Improveresonance frequencyVSAvoiddynamic deformation

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The support structure is divided into multiple discrete support beams distributed across the mirror substrate. This segmentation provides localized support at critical points without adding continuous mass, thereby reducing dynamic deformations while maintaining low overall mirror mass for high resonance frequency operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The support beams are strategically positioned at locations where they provide maximum structural reinforcement for minimal mass addition. The local quality of support is optimized by placing beams at specific regions of the mirror substrate that experience highest stress during operation, rather than uniformly distributing support mass across the entire mirror surface.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If support structures are added to the mirror, then dynamic deformations are reduced, but the mirror mass increases

Engineering Contradiction:

Improvedynamic deformationVSAvoidmirror mass

Core Design Contradiction:

Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

The support structure is divided into multiple discrete support beams distributed across the mirror substrate. This segmentation provides localized support at critical points without adding continuous mass, thereby reducing dynamic deformations while maintaining low overall mirror mass for high resonance frequency operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The support beams are strategically positioned at locations where they provide maximum structural reinforcement for minimal mass addition. The local quality of support is optimized by placing beams at specific regions of the mirror substrate that experience highest stress during operation, rather than uniformly distributing support mass across the entire mirror surface.

Inventive Principle:

Principle #3Local quality

3Speed

If the mirror is made thinner to reduce mass, then resonance frequency increases, but manufacturing precision becomes more difficult

Engineering Contradiction:

Improveresonance frequencyVSAvoidfabrication accuracy

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The support beams are integrated into the mirror substrate during the same fabrication process rather than being added as a separate post-processing step. This preliminary action ensures that the thin mirror structure and support beams are manufactured together as a single integrated component, maintaining precise geometric relationships and avoiding alignment errors that would compromise manufacturing precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The support structure and mirror substrate are merged into a single integrated component manufactured in one process. This combining of functions eliminates the need for separate assembly steps and ensures that the thin mirror structure maintains its structural integrity and precise dimensions throughout fabrication.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8922864B2MEMS device having reduced deformations

Publication Date: 2014.12.30 STMICROELECTRONICS INT NV

AI summary

A MEMS apparatus is provided for scanning an optical beam. The MEMS apparatus is formed out of a pre-fabricated multi-layer device and comprises at least one tilting micro-mirror formed in a first active layer of that pre-fabricated multi-layer device and a support structure formed in a second layer of the pre-fabricated multi-layer device, and wherein the support structure is preferably formed by etching parts of the second layer to obtain a pre-determined shape of the supporting structure.