mems (detail presentation)
TRANSCRIPT
Micro-Electro-Mechanical Systems
-The Future Technology, but Today’s choice
Presented by… Vinayak HegdeGuide: Mrs. Priti M
April 8, 2023 2
AIM OF MY PRESENTATION
To familiarize what the MEMS TECHNOLOGY is all about
To explain about Microfabrication Process.
Applications of the MEMS in various fields.
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Outline of My PresentationIntroductionHistorical Background
(MEMS Evolution)
Preparation Process of MEMS(Fabrication Process)
Applications of MEMS(Fields where MEMS Used)
Interrelationship between MEMS and Nano(Future Scope of MEMS)
Conclusion
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Introduction
What is MEMS Technology?MEMS technology is based on a number of tools and
methodologies, which are used to form small structures with dimensions in the micrometer scale
MEMS fabrication approach that conveys the advantages of miniaturization, multiple components, and microelectronics to the design and construction of integrated Electromechanical systems
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Introduction Conti…What are MEMS?
• Micro - Small size, microfabricated structures
• Electro - Electrical signal /control ( In / Out )
• Mechanical - Mechanical functionality (Out/ In )
• Systems - Structures, Devices, Systems controlsWhat is the size of MEMS?
They range in size from the sub micron level to the millimeter level, and there can be any number, from a few to millions, in a particular system.
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MEMS Scaling
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Building Blocks In MEMS
How MEMS are prepared? There are three basic building blocks in MEMS technology.
1. Deposition: The ability to deposit thin films of material on a substrate.
2. Lithography: To apply a patterned mask on top of
the films by photolithograpic imaging.
3. Etching: To etch the films selectively to the mask.
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MEMS Deposition TechnologyMEMS deposition technology can be classified in two groups:
1. Depositions that happen because of a chemical reaction: Chemical Vapor Deposition (CVD) Electrodeposition Epitaxy Thermal oxidation
2. Depositions that happen because of a physical reaction: Physical Vapor Deposition (PVD) Casting
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MEMS Lithography Technology
MEMS lithography technology can be classified in two groups:1. Pattern Transfer2. Lithographic Module
a. Dehydration bake and HMDS primeb. Resist spin/spray and Soft bakec. Alignment, Exposured. Post exposure bake and Hard bakee. Descum
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MEMS Etching Technology
There are two classes of etching process:
1. Wet etching: The material is dissolved when immersed in a chemical solution.
2. Dry etching: The material is sputtered or dissolved using reactive ions or a vapor phase etchant.
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Microfabrication Process
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PhotolithographyClean wafer : to remove particles on the surface as well as any traces of organic, ionic,
and metallic impuritiesDehydration bake: to drive off the absorbed water on the surface Coating
Coat wafer with adhesion promoting filmCoat with photoresist
Soft bake : to drive off excess solvent and to promote adhesionExposurePost exposure bake: to suppress standing wave-effectDevelop, Clean, Dry Hard bake: to harden the PR and improve adhesion to the substrate
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Photolithography
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Additive ProcessesOxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
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Additive Processes
Doping
Dopants : N type (Phosphorous, Arsenic), P type (Boron)
Doping Methods1. Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 – 1280 0C.
It is governed by Fick’s Laws of Diffusion.
Dopant ions bombarded into targeting substrate by high energy.
Ion implantation are able to place any ion at any depth in sample.
2. Ion Implantation
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Additive ProcessesPhysical Vapor Deposition (PVD)
1. EvaporationDeposition is achieved by evaporation or sublimation of heated metal onto substrate.
2. SputteringSputtering is achieved by accelerated inert ion by DC drive in plasma through potential gradient to bombard metallic target.
Then the targeting material is sputtered away and deposited onto substrate placed on anode.
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Additive ProcessesPhysical Vapor Deposition (PVD)
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Additive ProcessesChemical Vapor Deposition (CVD)
Materials deposited: Polysilicon, silicon nitride, silicon oxide, silicon carbide etc.
How does CVD Work?Gaseous reactants are introduced into chamber at elevated temperatures.Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD), PECVD (Plasma Enhanced CVD)
Salient FeaturesCVD results depend on pressure, gas, and temperatureCan be diffusion or reaction limitedVaries from film composition, deposition rate and electrical and mechanical properties
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Subtractive ProcessesDry Etching
Dry Chemical EtchingHF Etching
HF is a powerful etchant and hence, highly dangerous.
XeF2 Etching
2XeF2+Si→2Xe+SiF4 Isotropic etching (typically 1-3µm/min) Does not attack aluminum, silicon dioxide, and silicon nitride
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Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption, and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
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Subtractive Processes
Dry Etching
Deep Reactive Ion Etching (DRIE) A very high-aspect-ratio silicon etch method
DRIE Etched Pillars
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Subtractive Processes
Wet Etching
Isotropic Wet Etching
Isotropic etchants etch in all directions at nearly the same rate.
Commonly use chemical for Silicon is HNA (HF/HNO3/Acetic Acid) This results in a finite amount of undercutting
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Subtractive Processes
Wet Etching
Anisotropic Wet Etching
Anisotropic etchants etch much faster in one direction than in another.
Etchants are generally Alkali Hydroxides (KOH, NaOH, CeOH
Reaction :Silicon (s) + Water + Hydroxide Ions → Silicates + Hydrogen
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Metal Patterning
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Surface Micromachining
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MEMS Packaging
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Example: An insulin pump fabricated by classic MEMS technology
1. Pumping membrane 2. Pumping chamber
3. Inlet 4. Outlet
5. Large mesa 6. Upper glass plate
7. Bottom glass plate 8. patterned thin layer (for improved fluidics)
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MEMS Applications Micro-engines –Micro Reactors, Vibrating Wheel
Inertial Sensors –Virtual Reality Systems
Accelerometers –Airbag Accelerometer
Pressure Sensors –Air Pressure Sensors
Optical MEMS –Pill Camera
Fluidic MEMS -Cartridges for Printers
Bio MEMS -Blood Pressure Sensors
MEMS Memory Units -Flash Memory
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iPod Touch: Techno Sensitiveness
The two key elements of a
MEMS are: MEMS sensor, the silicon
mechanical element which senses the motion;
Interface chip, the IC which converts the motion measured by the sensor into an analog or digital signal.
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An implantable blood pressure sensor developed by
CardioMEMS
Bio MEMS Application
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MEMS Memory [Nanochip]
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MEMS driven Storage DevicesTB to PB device capacitiesMassively parallel data transfer
ratesVery fast file access times Improved reliability Smaller size and weight Device costs less than today's
devicesExcellent fit for applications to
enterprise
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Future of Magnetic Storage
HAMR-Heat Assisted Magnetic Recording or TAR -Thermally Assisted Recording
SOMA-Self Organized Magnetic Assemblies; a form of directed patterned media.
Super high coercivity storage layers (such as FePt) with stable grain sizes averaging < 2nm.
Super servos for (coarse/fine) tracking and flying height control.
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Advantages and Disadvantages
Minimize energy and materials use in manufacturing
Cost/performance advantages Improved reproducibility Improved accuracy and
reliability Increased selectivity and
sensitivity
Farm establishment requires huge investments
Micro-components are Costly compare to macro-components
Design includes very much complex procedures
Prior knowledge is needed to integrate MEMS devices
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ConclusionThe medical, wireless technology, biotechnology, computer, automotive and aerospace industries are only a few that will benefit greatly from MEMS.
This enabling technology promises to create entirely new categories of products
MEMS will be the indispensable factor for advancing technology in the 21st century
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References for MEMSIEEE Explore http://ieeexplore.ieee.org/Xplore/DynWel.jspPDF Files http://www.scribd.com/mems/
Introduction to Microengineering http://www.dbanks.demon.co.uk/ueng/MEMS Clearinghouse http://www.memsnet.org/MEMS Exchange http://www.mems-exchange.org/
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