This article discusses MEMS, i.e. Micro-Electro Mechanical Systems. It gives a rudimentry idea of MEMS technology, its block diagram, applications, advantages and disadvantages. It also gives a brief idea on the working principle of MEMS devices.

1. MEMS
Introduction

2. Contents:
1. Definition
2. Interdisciplinary Technology
3. MEMS Process Block Diagram
4. MEMS Characteristics
5. MEMS Device Size
6. MEMS Switching Types
7. Advantages of MEMS
8. Disadvantages of MEMS
9. MEMS Applications
10. Basic Fabrication Steps of MEMS
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3. MEMS Introduction – Definition:
 MEMS stands for Micro-Electro Mechanical Systems.
 Definition - A technological process to design and develop miniature integrated devices that
comprise both mechanical and electrical-electronic components.
 MEMS consists - Central Processing Unit (CPU), and static and moving components interacting
with the surrounding environment, i.e. micro-sensors.
 Called as MEMS in USA, Micro-Machines (MM) in Japan and Microsystem Technology (MST)
in Europe.
 Umbrella term for a wide range of micro-fabrication designs, methods and mechanisms that
involve realizing moving mechanical parts at microscopic scale.
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4. MEMS – Interdisciplinary Nature:
 Inter-disciplinary Engineering –
Mechanical Engineering, Material Science,
Chemical Engineering, Design Engineering,
Electrical Engineering, Electronics Engineering,
Optical Engineering and Instrumentation Engineering.
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Fig. 1. MEMS Interdependence

5. MEMS – Manufacturing Process Block Diagram:
 Comprehensive Block Diagram of MEMS Manufacturing Process.
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Fig. 2. Block Diagram of MEMS Manufacturing

6. MEMS – Characteristics:
 The intrinsic characteristics of MEMS-based devices are:
1. Miniaturization (1 μm to 1 cm)
2. Electronic Integration
3. Precision Control of Physical Dimensions.
4. Parallel Fabrication
5. Cost Effective Batch Fabrication.
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7. MEMS – Characteristics:
 Miniaturization leads to:
1. High resonance frequency (ranging from Hz to MHz).
2. Enhanced sensitivity (output at 5 psi / 34 kPa / 345 mbar at 100 millivolts (mV)).
3. Good Stability (greater accuracy with marginal drift).)
4. Low thermal mass and thermal hysteresis (thermal hysteresis offset of <0.05% FSO).
 Electronic Integration leads to:
1. Seamless integration of mechanical sensors and actuator with electronic processors.
2. Monolithic integration (complete circuit on a single piece of silicon).
3. Improved signal quality due to reduced noise.
 Parallel Fabrication leads to:
1. High aspect ratio (ratio of width to height).
2. High uniformity across wafer.
3. High precision and multidimensional features.
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8. MEMS – Device Size:
 Fabricated by using IC batch process manufacturing techniques.
 Miniaturized size leads to consumes low power, and maintaining of very high isolation.
 Comprises – simple static to complex structures multi-moving parts.
 Size – Few micro-meters to millimetres.
 Influence – Macro-scale control elements and devices.
 Built of components - 1 and 100 μm in size (i.e., 0.001 to 0.1 mm).
 MEMS device range - 20 μm to 1 millimetre (i.e., 0.02 to 1.0 mm).
 Although components arranged in arrays (e.g., digital micro-mirror devices) can be more than
𝟏𝟎𝟎𝟎 𝒎𝒎𝟐.
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9. MEMS – Switch Types:
There are two basic types of MEMS switching technology: Capacitive and Ohmic.
1. Capacitive MEMS switches are developed using a moving plate or sensing element, which
changes the substrate capacitance (right-hand figure).
2. Ohmic MEMS switches are controlled by electrostatically controlled cantilevers (left-hand
figure).
 Ohmic MEMS switches can fail from metal fatigue of the MEMS actuator (cantilever) and
contact wear, since cantilevers can deform over time.
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Electrostatic discharge (ESD) is a sudden and momentary flow of electric current between two electrically charged objects caused by
contact, an electrical short or dielectric breakdown.

10. MEMS – Advantages:
 Advantages of MEMS:
1. Small size, dimension & weight.
2. Consumption of very low power.
3. High productivity (Batch fabricated in large arrays).
4. Superior performance & Wide range compatibility.
5. Low cost.
6. Easy to integrate and modify into systems.
7. Small thermal constant, & Improved thermal expansion tolerance
8. Negligible thermal hysteresis.
9. Resistant to shock, vibration and radiation.
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11. MEMS – Disadvantages:
 Drawbacks in MEMS:
1. Significant power transfer is challenging due to their excessive miniaturized size.
2. The wafer material cannot be exposed to large loads as that might damage the wafer.
3. High cost involvement in the Research & Development stages.
4. It is still a developing field, and therefore reliability at times is a concern.
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12. MEMS – Applications:
 MEMS - capable to sense, control and actuate on micro scales.
 MEMS - applications in electronic control and bio-sensing applications.
 MEMS devices find widespread applications in:
1. Navigation field.
1) Marine environment and Geo-mapping.
2) Natural Resource Identification like Oil and Gas exploration.
2. Environmental Studies.
1) MEMS barometer.
2) Weather predictions.
3) Water quality monitor.
4) Aquatic and ocean ecology studies.
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13. MEMS – Applications:
3. Bio medical applications.
1) Bio-cavity Laser to distinguish between cancerous and non-cancerous cells.
2) Smart Pill – body implantation and automatic drug delivery.
3) Synthetic Eyesight – MEMS based array inserted in retina to instil partial vision.
4) Lab-On-Chip, Micro Total Analyser, embedded medical devices, viz. stents.
4. Security and surveillance.
1) MEMS gyroscope in drones.
2) Inertial Navigation System (INS) to facilitate auto-pilot.
5. Military Operation.
1) Pressure sensing for anti-torpedo weaponry.
2) Submarine Detection.
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14. MEMS – Applications:
6. High frequency circuit designs.
1) Micro-actuation in micro-scale devices.
2) MEMS switches.
3) Micro-pumps.
4) Micro-levers.
5) Micro-grippers
7. Micro scale Energy Harvester
1) Micro-piezoelectric crystals.
2) Electrostatic energy harvesters.
3) Electromagnetic energy harvesters.
8. Microscopy
1) Scanning probe microscope.
2) Atomic Force microscope.
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15. MEMS – Applications:
The table below highlights the major MEMS applications.
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Automotive Electronics Medical Communication Defence
Internal Navigation Disk Drive heads Blood Pressure Sensors Fibre-optic network
components
Munitions guidance
Air conditioning
compressor sensors
Inkjet printer heads Muscle stimulators and
drug delivery system.
RF Relays, switches and
filters
Surveillance.
Brake force sensors,
suspension control
accelerometers.
Projection screen
television.
Implanted pressure
sensors.
Projection displays in
portable communication
devices.
Arming systems.
Fuel level and
vapour pressure
sensors.
Earthquake sensors. Prosthetics. Voltage Controlled
Oscillators (VCO)
Embedded Sensors.
Airbag sensors. Avionics pressure
sensors.
Miniature analytical
instruments.
Splitters and couplers. Data storage.
Intelligent tyres. Mass data storage
systems.
Pacemakers. Tuneable LASER Aircraft/ Missile
Control.

16. MEMS – Basic Fabrication Steps:
 MEMS became practical once they could be fabricated using modified semiconductor device
fabrication technologies, normally used is Electronics.
 MEMS fabrication steps:
1. Moulding and Plating (Deposition – Physical and Chemical)
2. Patterning (Lithography)
3. Ethching (Wet & Dry)
 Wet etching (KOH – Potassium Hydroxide, TMAH – Tetra-methyl-ammonium
Hydroxide)
 Dry etching (RIE - Reactive Ion Etching and DRIE – Deep Reactive Ion Etching),
4. Electrical Discharge Machining (EDM),
5. Micro-machining (Bulk, Surface, High Aspect Ratio (HAR)).
6. Packaging
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17. References:
1. P.C https://www.mems-exchange.org/MEMS/what-is.html
2. P.C https://www.bosch-sensortec.com/about-us/our-company/mems-expertise/
3. P.C https://wpo-altertechnology.com/mems-packaging/
4. Gabriel K, Jarvis J, Trimmer W (1988). Small Machines, Large Opportunities: A Report on the Emerging
Field of Microdynamics: Report of the Workshop on Microelectromechanical Systems Research. National
Science Foundation (sponsor). AT&T Bell Laboratories.
5. Waldner JB (2008). Nanocomputers and Swarm Intelligence. London: ISTE John Wiley & Sons.
p. 205. ISBN 9781848210097.
6. Angell JB, Terry SC, Barth PW (1983). "Silicon Micromechanical Devices".
7. Sci. Am. 248 (4): 44–55
8. Bibcode:1983SciAm.248d..44A. doi:10.1038/scientificamerican0483-44.
9. Dirk K. de Vries (2005). "Investigation of gross die per wafer formulas". IEEE Transactions on
Semiconductor Manufacturing. 18 (February 2005): 136–139.
10. https://en.wikipedia.org/wiki/Flexural_strength
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