INNOVATIVE APPROACH IN MICRO-ELECTROMECHANICAL

SYSTEM (MEMS)

Outline

MEMS Introduction

Sensor and its type

Fabrication

MEMS Manufacturing Technology

Applications

Conclusion

References

What is MEMS?

MEMS or Micro-Electro Mechanical System is a technique of combining Electrical and Mechanical components together on a chip, to produce a system of miniature dimensions.

MEMS is the integration of a number of micro-components on a single chip which allows the microsystem to both sense and control the environment.

The components are integrated on a single chip using micro fabrication technologies.

What is a Sensor?

A device used to measure a physical quantity(such as temperature) and convert it into an electronic signal of some kind(e.g. a voltage), without modifying the environment.

What can be sensed?Almost Everything!!!Commonly sensed parameters are:

Pressure Temperature Flow rate Radiation Chemicals Pathogens

N

S

EW 2 Axis Magnetic Sensor

2 Axis Accelerometer

Light Intensity Sensor

Humidity Sensor

Pressure Sensor

Temperature Sensor

But why MEMS for sensors?

Smaller in size

Have lower power consumption

More sensitive to input variations

Cheaper due to mass production

Less invasive than larger devices

Type of Sensors

MechanicalSensors

• Strain Gauges• Accelerometers• Pressure Sensors• Microphones• Gyroscopes(Rotati

on Rate)

OpticalSensors

• Direct Sensors (Light Electronic Signal)

• Indirect Sensors (Light Intermediate Energy Electronic Signal)

• Biological Light Sensors

ThermalSensors

• Thermo mechanical (Dimension)

• Thermo Resistive (Resistance)

• Acoustic (Sound)• Biological

Chemical & Biological Sensors

• Electronic Nose• Electronic Tongue

Fabrication

Materials used are:

Silicon

Polymers

Metals

Ceramics

Basic Process

Deposition Patterning Etching

Basic Process of Fabrication

Deposition Deposition that happen because of a chemical reaction or physical reaction.

Patterning The pattern is transfer to a photosensitive material by selective exposure to a radiation

source such as light. If the resist is placed in a developer solution after selective exposure to a light source, it will etch away.

Etching Etching is the process of using strong acid to cut into the unprotected parts of a metal

surface to create a design in. There are two classes of etching processes:

Wet Etching Dry Etching.

MEMS Manufacturing Technology

Bulk Micromachining

Surface Micromachining

High Aspect Ratio (HAR) Silicon Micromachining

MEMS Manufacturing Technology

This technique involves the selective removal of the substrate material in order to realize miniaturized mechanical components.

A widely used bulk micromachining technique in MEMS is chemical wet etching, which involves the immersion of a substrate into a solution of reactive chemical that will etch exposed regions of the substrate at very high rates.

Bulk Micromachining

Etched grooves using

(a) Anisotropic etchants,

(b) Isotropic etchants,

(c) Reactive Ion Etching (RIE)

MEMS Manufacturing Technology

In surface micromachining, the MEMS sensors are formed on top of the wafer using deposited thin film materials.

Surface Micromachining

(a) Spacer layer deposition.

(b) Pattering of the spacer layer.

(c) Deposition of the microstructure layer.

(d) Patterning of desired structure.

(e) Stripping of the spacer layer resolves final structure.

MEMS Manufacturing Technology

HAR combines aspects of both surface and bulk micromachining to allow for silicon structures with extremely high aspect ratios through thick layers of silicon (hundreds of nanometers, up to hundreds of micrometers).

HAR MEMS technology enables a high degree of immunity to high-frequency, high-amplitude parasitic vibrations.

High Aspect Ratio (HAR) Silicon Micromachining

Applications in Medical Science

Biocavity Laser : This device distinguishes cancerous from non cancerous cells thus aiding the surgeons in operations.

Smart Pill : Implanted in the body Automatic drug delivery (on demand)

Sight for the blind : MEMS based array that may be inserted in the retina of a blind person to provide partial sight

Applications in Marine Science

Sensing in marine environment maybe done for various reasons:

Oil exploration and related applications

Global weather predictions

Monitor water quality for any contamination

Measure parameters detrimental to the “health” of structures in the sea ( like oil rigs and ships )

Study of aquatic plants and animals

In military operations

Applications in Marine Military Operations

An array of MEMS sensors spread on the ocean floor could detect the presence of enemy submarines.

MEMS sensors (pressure sensors, accelerometers etc.) are being used in anti-torpedo weapons on submarines and ships.

MEMS sensors in torpedoes are responsible forDetonating the torpedo at the right timeHitting the target in a crowded

environmentPrevent any premature explosion

CONCLUSION

MEMS promises to be an effective technique of producing sensors of high quality, at lower costs.

Thus we can conclude that the MEMS can create a proactive computing world, connected computing nodes automatically, acquire and act on real-time data about a physical environment, helping to improve lives, promoting a better understanding of the world and enabling people to become more productive.

References

X. Wang, J. Engel, C. Liu, J. Micromech. Microeng. 2003, 13, 628.

Christian A. Zorman, Mehran Mehregany, MEMS Design and Fabrication, 2nd Ed. 2,16.

Ms. Santoshi Gupta, MEMS and Nanotechnology IJSER, Vol 3, Issue 5,2012

Stephen Beeby, MEMS Mechanical Sensor, PP. 7

Lenz, J., Edelstein, A.S., "Magnetic sensors and their applications." IEEE Sensors J. 2006, 6, 631-649.

Sinclair M J 2000 A high force low area MEMS thermal actuator Proc. 7th Intersociety Conf. on Thermal and Thermomechanical Phenomena (Las Vegas, NV) pp 127–32

R. Ghodssi, P. Lin (2011). MEMS Materials and Processes Handbook. Berlin: Springer.

Chang, Floy I. (1995).Gas-phase silicon micromachining with xenon difluoride. 2641. pp. 117.

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