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 MEMs Fabrication Alek Mintz  MEMs Fabrication Alek Mintz

MEMs Fabrication Alek Mintz - PowerPoint Presentation

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MEMs Fabrication Alek Mintz - PPT Presentation

22 April 2015 Abstract Microelectromechanical Systems MEMS are devices that integrate mechanical systems with electronic circuits Fabrication of MEMS involves the use of specialized micromachining technologies Device packaging aims to protect from outside damage and varies drastically depe ID: 776345

etching micromachining mems packaging etching micromachining mems packaging bulk fabrication surface silicon bonding high technologies wafer mechanical systems etch

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Presentation Transcript

Slide1

MEMs Fabrication

Alek Mintz22 April 2015

Abstract

Microelectromechanical Systems (MEMS) are devices that integrate mechanical systems with electronic circuits. Fabrication of MEMS involves the use of specialized micromachining technologies. Device packaging aims to protect from outside damage and varies drastically depending upon application. Different materials used, fabrication techniques, and packaging types will be examined.

Key Words: Surface Micromachining, Bulk Micromachining, LIGA Lithography, Isotropic Etching, Anisotropic Etching, XeF2 Etching, MEMS Packaging

Slide2

Outline

Materials

Bulk and Surface Micromachining

Etching and Deposition Techniques

Other Manufacturing Technologies

Wafer Bonding

Device Packaging

Slide3

What are MEMS?

Small devices that use electrical and mechanical elements

Common uses include sensors and actuators

Made using modified semiconductor fabrication technology

Slide4

Materials

SiliconPolymersMetalsCeramics

Slide5

Manufacturing Technologies

Bulk MicromachiningSurface Micromachining

Slide6

Bulk Micromachining

Oldest technologyInvolves selective removal of substrate materialCan be done through physical or chemical meansEtching requires a masking material

Slide7

Bulk MicromachiningAdvantages/Disadvantages

Can be done much fasterCan make high aspect ratio partsCheaper

Not easily integrated with microelectronics

Part complexity must be relatively simple

Part size is limited to being larger

Slide8

Slide9

Surface Micromachining

Newer than Bulk MicromachiningUses single sided wafer processingInvolves use of sacrificial and structural layersProvides more precise dimensional controlInvolves use of sacrificial and structural layers

Slide10

Surface Micromachining Advantages/Disadvantages

Possible to integrate mechanical and electrical components on same substrateCan create structures that Bulk Micromachining cannotCheaper glass or plastic substrates can be used

Mechanical properties of most thin-films are usually unknown and must be measured

Reproducibility of mechanical properties can be difficult

More expensive

Slide11

Slide12

Deposition Techniques

SputteringEvaporationChemical Vapor Deposition – LPCVD, PECVDThermal Oxidation

Slide13

Isotropic Etching

Etching does not depend on crystal orientationEtch rate of some etching solutions are dependent on dopant concentrationsSolution is stirred to keep homogeneity and allow for optimal etching

Slide14

Anisotropic Etching

Etch rates are dependent upon crystal orientation

Used more widely for Silicon micromachining

Allows for different etching shapes and better dimensional control

Slide15

Etching

Wet and dry etching

Uniformity of etching can vary across substrate

Timed etches difficult to control

Dopant and Electrochemical etch stops are used to control etch depth

Slide16

Plasma Etching

Gas usually contains molecules rich in Cl or FCCl4, CH3FPlasma ashing

Slide17

Deep Reactive Ion Etching (DRIE)

Relatively new technologyEnables very high aspect ratio etchesUses high density plasma to alternately etch and deposit etch resistant polymer on sidewalls

Slide18

Lithographie Galvanoformung Adformung (LIGA)

Popular high aspect ratio micromachining technologyPrimarily non-Silicon basted and requires use of x-ray radiationSpecial mask and x-ray radiation makes process expensive

Slide19

Slide20

Hot Embossing

Mold insert is made with inverse patternSubstrate and polymer are heated and force is applied to create structureProcess can replicate complicated, deep featuresPart costs very low compared to other technologies

Slide21

XeF2 Etching

Chemical etchantHigh Silicon selectivityStiction-free release

Slide22

Laser Micromachining

Lasers generate intense energy quicklyFocusing optics used to melt or vaporize materialCan produce very small features

Slide23

Wafer Bonding

Silicon and Glass wafers can be bonded together to create systems using several parts

Bond using high temperatures

Bond using much lower temperature and large voltage

Slide24

Eutectic Bonding

Bonding of Silicon substrate to another using intermediary level of gold

Slide25

Packaging

MEM die is extremely fragileMust offer protection, connections to device, heat removal capabilitiesGoal is to minimize size, cost, mass, complexity

Slide26

Packaging Design

Thermal shock, vibration, acceleration, particles, radiation, electric + magnetic fields

Thermal expansion of packaging must be equal or slightly greater than that of Silicon

to prevent cracking

Slide27

Packaging Types

Metal

Ceramic

Plastic

Thin-Film Multilayer

Slide28

Conclusion

MEMS fabrication uses highly specialized technology

Devices are made using Bulk or Surface micromachining or a combination

Isotropic and Anisotropic etching

Popular etching and microstructure fabrication technologies

Wafer Bonding

Packaging types and considerations

Slide29

References

"Fabricating MEMS and Nanotechnology." 

MEMS and Nanotechnology Exchange

. Web. 18 Apr. 2015. <https://www.mems-exchange.org/MEMS/fabrication.html

>.

Gerke

, R. "MEMS Packaging." 

University of Pennsylvania

. Web. 18 Apr. 2015. <http://www.seas.upenn.edu/~meam550/PackagingJPL.pdf

>.

"Introduction to Microelectromechanical Systems (MEMS)." 

Brigham Young University

. Web. 18 Apr. 2015. <https://compliantmechanisms.byu.edu/content/introduction-microelectromechanical-systems-mems

>.

Slide30

Key Concepts

Advantages and Disadvantages of Bulk and Surface Micromachining

Anisotropic and Isotropic etching

XeF2 etching

Wafer Bonding

Device Packaging considerations