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
Download Presentation The PPT/PDF document " MEMs Fabrication Alek Mintz" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
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
Slide2Outline
Materials
Bulk and Surface Micromachining
Etching and Deposition Techniques
Other Manufacturing Technologies
Wafer Bonding
Device Packaging
Slide3What are MEMS?
Small devices that use electrical and mechanical elements
Common uses include sensors and actuators
Made using modified semiconductor fabrication technology
Slide4Materials
SiliconPolymersMetalsCeramics
Slide5Manufacturing Technologies
Bulk MicromachiningSurface Micromachining
Slide6Bulk Micromachining
Oldest technologyInvolves selective removal of substrate materialCan be done through physical or chemical meansEtching requires a masking material
Slide7Bulk 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
Slide8Slide9Surface 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
Slide10Surface 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
Slide11Slide12Deposition Techniques
SputteringEvaporationChemical Vapor Deposition – LPCVD, PECVDThermal Oxidation
Slide13Isotropic 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
Slide14Anisotropic Etching
Etch rates are dependent upon crystal orientation
Used more widely for Silicon micromachining
Allows for different etching shapes and better dimensional control
Slide15Etching
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
Slide16Plasma Etching
Gas usually contains molecules rich in Cl or FCCl4, CH3FPlasma ashing
Slide17Deep 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
Slide18Lithographie 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
Slide19Slide20Hot 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
Slide21XeF2 Etching
Chemical etchantHigh Silicon selectivityStiction-free release
Slide22Laser Micromachining
Lasers generate intense energy quicklyFocusing optics used to melt or vaporize materialCan produce very small features
Slide23Wafer 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
Slide24Eutectic Bonding
Bonding of Silicon substrate to another using intermediary level of gold
Slide25Packaging
MEM die is extremely fragileMust offer protection, connections to device, heat removal capabilitiesGoal is to minimize size, cost, mass, complexity
Slide26Packaging 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
Slide27Packaging Types
Metal
Ceramic
Plastic
Thin-Film Multilayer
Slide28Conclusion
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
Slide29References
"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
>.
Slide30Key Concepts
Advantages and Disadvantages of Bulk and Surface Micromachining
Anisotropic and Isotropic etching
XeF2 etching
Wafer Bonding
Device Packaging considerations