MEMS

Micro-Electro-Mechanical Systems

MEMS: –

What is MEMS?

MEMS known as Micro-Electro-Mechanical Systems is a process technology used to create tiny integrated devices or systems that combine mechanical and electrical components.

Introduction: –

It is generally a collaboration of two or more than two different streams like Mechanical + Electrical + Information Technology.

It is a technique of collaboration of Electrical and Mechanical components together on probably a chip, to produce a system of possibly smallest dimensions of the product. By possibly smallest or miniature, we mean dimensions less than the thickness of human hair or skins!!!!

Some Examples like Micro Cluster, DENSO Micro-Car,

The Ultra Miniature can be used in medical instruments like pressure sensors i.e. Ultra-high resolutions pressure sensor.

So, MEMS are fabricated using integrated circuit (IC) batch processing techniques and can range in size from a few micrometers to millimeters.

These devices (or systems) can use for sense, control, and actuate on the micro-scale, and generate effects on the macro scale.

Definition: –

Micro-Electro-Mechanical Systems (MEMS) is the integration of mechanical elements, sensors, actuators, and electronics on a common substrate through the utilization of microfabrication technology or “microtechnology”.

@inproceedings{Rijal2018DesignAS, title={Design and Simulation of Micro-cantilever}, author={Suresh R. Rijal and C. K. Thadani and Chetana Kurve and Shrikant S. Chamlate}, year={2018} }

The interdisciplinary nature of MEMS utilizes design, engineering, and manufacturing expertise from a wide and diverse range of technical areas including integrated circuit fabrication technology, mechanical engineering, materials science, electrical engineering, chemistry, chemical engineering, fluid engineering, optics, instrumentation, and packaging.

International Journal Of Modern Engineering Research (IJMER),
Micro-Electromechanical Systems (Mems)
R. U. Sonje, S. V. Borde
 Mechanical Department, Govt. Polytechnic, Nashik, Nashik, Maharashtra (India)

Applications: –

  • MEMS can be found in manufacturing and production systems such as, automotive, medical, electronic, communication, and defense applications.
  • accelerometers for airbag sensors,
  • inkjet printer heads,
  • computer disk drive read/write heads,
  • projection display chips,
  • blood pressure sensors,
  • optical switches,
  • microvalves,
  • biosensors.
AutomotiveElectronicsMedicalCommunicationsDefence
Internal navigation sensorsDisk drive headsBlood pressure sensorFibre-optic network componentsMunitions guidance
Air conditioning compressor sensorInkjet printer headsMuscle stimulators & drug delivery systemsRF Relays, switches and filtersSurveillance
Brake force sensors & suspension control accelerometersProjection screen televisionsImplanted pressure sensorsProjection displays in portable communications devices and instrumentationArming systems
Fuel level and vapour pressure SensorsEarthquake sensorsProstheticsVoltage controlled oscillators (VCOs)Embedded sensors
Airbag sensorsAvionics pressure sensorsMiniature analytical instrumentsSplitters and couplersData storage
“Intelligent” tyresMass data storage systemsPacemakersTuneable lasersAircraft control

Few examples on 3-D Micro machined Structures: –

  • Linear Rack Gear Reduction Drive
  • Triple-Piston Micro steam Engine
  • 2 dust mites on an optical shutter
  • Deflection of laser light using a mirror arrangements
  1. Basic micro-fabrication technologies: –
  2. Deposition
    1. Chemical vapor deposition (CVD/PECVD/LPCVD)
    2. Epitaxy
    3. Oxidation
    4. Evaporation
    5. Sputtering
    6. Spin-on methods
  3. Etching                                      
    1. Wet chemical etching                          
      1. Isotropic                                            
      2. Anisotropic
    2. Dry etching
      1. Plasma etch
      2. Reactive Ion etch (RIE, DRIE)
  4. Patterning
    1. Photolithography
    2. X-ray lithography
  5. Micromachining Processes
    1. Bulk micromachining
    2. Surface micromachining
    3. Isotropic etching
    4. Anisotropic etching
    5. Dissolved wafer process
    6. Deep Reactive Ion Etching
    7. Anodic and fusion bonding

Here we are going to discuss the main process of MEMS.

  1. Photo-lithography
Photolithography (image source: – Google)
  • Photolithography is the photographic technique to transfer prototypes of a standard or approved pattern, usually a circuit layout in IC applications, onto the surface of a substrate of some material (usually a silicon wafer).
  • The substrate is coated with a thin layer of material, usually silicon dioxide (SiO2), wherein the silicon wafers, on which a required pattern of holes will be generated.
  •  A thin film of an organic polymer, which is almost the attraction on ultraviolet radiation, will be deposited on the layer of oxide; this process is known as photoresist.
  • The radiation causes a chemical reaction in the affected areas of the photoresist, there are two types: positive and negative. A positive photoresist is strengthened by UV radiation whereas negative photoresists are weakened.
  • The resulting photoresist pattern is either the positive or negative image of the original pattern of the photomask.

    2. Bulk Micro-machining
  • Bulk micromachining involves the part removal of the bulk substrate.
  •  It is a subtractive process that uses wet or a dry etching method such as reactive ion etching (RIE), which helps to creates desired pits, grooves, and channels.

Materials typically used for wet etching such as silicon and quartz, while dry etching is conventionally used with silicon, metals, plastics, and ceramics.

So, there are two main comparisons for the best suitable etchants in real-life applications.

  1. Isotropic etchant: –
    Etches in all directions
    Forms rounded
    The most common solution – HNA: Mixture of HF, HNO3, Acetic acid (CH3COOH)
  2. Anisotropic etchant: –
    Directional dependant etch; based on crystal planes
    Forms flat
    The most common solution – EDP, KOH, TMAH

MEMS-based Microsystems

  • Highly integrated systems                        
  •        Sensing                                                            
  •        Actuation                                                         
  •       Computation                                           
  •       Control                                                
  •       Communication

These are energy domains

MechanicalThermalChemical         Radiant MagneticElectrical
forcetemperatureconcentrationphasefield intensityvoltage
pressureentropycompositionwavelengthflux densitycurrent
velocityheatreaction ratepolarization reflectancemagnetic momentcharge
accelerationheat flowrefractive indexpermeabilityresistance
positiontransmittancecapacitance
electromagnetic wave intensitypolarization

Common materials for MEMS: –

Silicon materials, Metal, Metal alloy, Ceramics, Polymers Nickel,  Copper, Gold

Thanks. Have a positive day…!

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