MEMS: Introduction and

Orientation
MEMS is the integration of mechanical elements ,sensors, actuators
and electronics on a common substrate through utilization of micro-
fabrication technology or Micro-technology

Micromachines : Japan
Microsystem Technology : Europe
 Sensors and Actuators

Transducer
Transducers are the devices which convert energy from
one form to another. So, a transducer can either be a
sensor or an actuator or both.
Sycamore measures just 8.41 x 9
x 1.13 mm and weighs only 150
milligrams. It is one-seventh the
size of a conventional dynamic-
driver package and one-third the
thickness, which is critical when
integrating into ever-thinner
electronics like smart watches and
glasses. As an all-silicon, solid-
state µSpeaker, Sycamore is IP58
rated to be rugged and sweat-
resistant for active users.
Tire pressure sensors play a crucial role when it comes to safety and efficiency in road traffic – whether for motorcycles, trucks, cars or
buses. They help to extend tire life, reduce fuel consumption and increase vehicle safety. Tire pressure monitoring systems (TPMS) are
already required by law for passenger cars in many regions of the world, including Europe, the USA and China.

SMP290
The SMP290 is based on Bosch’s MEMS technology and is one of the first fully integrated solutions with a Bluetooth interface. The sensor
combines all essential components for TPMS. These include a microcontroller, Bluetooth interface, and a two-axis acceleration sensor, as
well as pressure and temperature sensors. The SMP290 features a high level of integration and is said to have extremely low power
consumption, which enables an operating lifespan of up to 10 years.
Year 2024
 The company has used
silicon
microelectromechanical
systems (MEMS) to produce
an entirely new wristwatch
motor for analog watches
that’s half the size and
These
roughlywatches
threehavetimes
many ofas the
functions
efficient of
in smartwatches—pulse
comparison with
and sleep monitoring,
the standard stepper motorfitness
tracking,
now used in wristwatches. Bluetooth
communications, message
displaying—along with physical
hands, like a traditional analog
watch and, of course, a motor.
Because hybrid timepieces must
combine that motor with a variety
of electronic sensors and a
display, the watches are typically
quite large, and space inside the
case is usually very tight.
Nano satellites, also known as CubeSats or
NanoSats, are small satellites that typically weigh
less than 10 kilograms, measuring from 10
centimetres to 10 x 10 x 11.35 centimetres in size.

They are an inexpensive way to send a satellite into

orbit and have become increasingly popular in the
aerospace industry. Nano satellites provide a range
of applications including communications, Earth
observation, remote sensing, and scientific research.
Revolutionizing Key Sectors with MEMS Miniaturization, Integration and
Intelligence

Consumer Electronics
•Powering smart features in phones, wearables, homes
•Enable motion sensing, voice control, and environmental monitoring
Automotive
•Core to autonomous driving & safety systems
•Enhance navigation, stability, and vehicle connectivity
Healthcare
•Vital for remote care, wearables & implants
•Real-time tracking of heart rate, BP, glucose, etc.
Industry & Communication
•Drive IIoT, smart manufacturing, and network optimization
•Monitor equipment health, environment & signal quality
Future Outlook
•Smarter, smaller, energy-efficient sensors
•Key enablers of Smart Cities, AgriTech, and next-gen IoT
Capsule endoscopy/
Drug Delivery
MEMS: Introduction and Orientation
• Goals:
To analyze and study the MEMS transducers utilizing principle of sensing
and actuation, properties of materials available for fabrication,
microfabrication technologies and understanding of circuit and system
issues, packaging,calibration and test.

• Topics: - Introduction and Orientation (1)

- Basic Electrical &Mechanical concepts (2)
- Transduction Methods (12)
Electrostatic/Thermal/Piezoresistive/
Piezoelectric/Magnetic Sensing & actuation
- Materials for MEMS (3)
- Fabrication Technologies ( 7)
- RF MEMS (5)
- Optical MEMS ( 4)
- Micro-fluidics (2)
- Chemical & Bio MEMS (2)
- Packaging & testing (2)
MEMS:Introduction and Orientation
• References:
1. Foundations of MEMS
Chang Liu,Illinois ECE series,Pearson International edition
2. MEMS& Microsystems Design and Manufacturing
Tai-Ran Hsu,Tata McGraw-Hill
3. An Introduction to microsystem Engineering
N.Maluf,Artech House,2000
4. Micromechanical Source book
G.Kovas,McGrawhill 1998
5. Fundamentals of Microfabrication
M.Madau,2nd edition,CRC Press,2002
5. RF MEMS Theory,Design & Technology
G.M.Rebeiz,John –Willey,2003
6. Microsystem Design
S.D.Senturia Kluwer Academic Publications
7. Optical MEMS
 EVOLUTION OF MEMS TECHNOLOGY
1947 Invention of Transistor by Schockley,Bardeen and Brattain
1954 Piezoresistive effect in semiconductors ( C.S.Smith)
1955 Concept of integration by Jack Kilby at TI and Robert Noyce at Fairchild

Integrated Circuit technology : 1960 -80 Sparce activity on MEMS

Moore,s Law

1959 “ There is plenty of room at the bottom” ( R.Feynman)

1962 Silicon Integrated Piezo Actuators (O.N.Tufte et.al)
1965 Surface Micromachined FET Accelerometer ( H.C.Nathanson et.al.)
1967 Resonant Gate Transistor (RGT) at Westinghouse
1970 Diaphram type silicon micro-machined pressure sensor
1977 Silicon Electrostatic Accelerometer ( Stanford)
1978 Ink jet Printers by HP
1982 “Silicon as a Mechanical Material” ( K.Peterson)
1983 Integrated pressure sensor
1985 LIGA ( W.Ehrfeld)
1986 Silicon Wafer Bonding ( M.Shimbo)
1988 Batch fabricated Pressure Sensor via Wafer bonding (Nova Sensor)
 EVOLUTION OF MEMS TECHNOLOGY

1990 The term MEMS was coined

1992 Bulk Micromachining ( SCREAM Process)
- Integrated Inertia Sensors (ADXL) by Analog Devices for automotive
air bag development
1993 Digital light processing chips by TI for projection display
1999 Optical Network Switch

MEMS related Technologies

* Optical MEMS ( MOEMS)
* RF MEMS
* Microfluidics
* Bio MEMS
Why MEMS?

What is Scaling?
 Why MEMS?
MEMS SCALING ISSUES

A simple example:

The volume scales by a factor of 1000

Surface area scales by only a factor of 100
So, after miniaturization, Surface effects dominate 10 times
as against before miniaturization
Example of a dominant surface effect:

Consider a miniaturized electrochemical battery.

As the charge holding capacity varies linearly with volume, a

decrease of 1000 times

Consider a miniaturized solar cell, as charging capacity depends on

surface area, a decrease of ONLY 100 times!

So, after miniaturization, solar cell is 10

times better in performance if the two
were alike before miniaturization.
 Scaling effects on a cantilever beam

Dimensions: L, b and h (length, width and thickness, respectively).

Density of the material : ρ,
The mass of the cantilever is: M = Lbhρ
The elastic constant along the z-direction can be expressed as: Kz = 12YI / L3
where Y is the material’s Young modulus and I is the cross-sectional
momentum of inertia, which is proportional to bh3.
Taking s as the generic linear dimension,
M scales as s3, and Kz scales as s, or linearly with s.

One of the after effects of miniaturization:

If the linear dimensions of this cantilever are scaled by a factor of 10,

isomorphically, say s’ = 0.1s, then the corresponding scaled mass and
elastic constant are, respectively:
M ‘= 0.001M and K’z = 0.1Kz.

This means that the 10 times linearly

scaled cantilever is 1000 times lighter, but
only 10 times less stiff than its non-scaled
counterpart; therefore, the scaled version
has an improved mechanical robustness !!!!!!!
 Cantilever contd...
Scaling of resonance frequency
The vibrating cantilever may be used as a mass sensor by
measuring its resonance frequency shift with respect to a
reference, or ‘unloaded’, value ω0, due to a change in the mass.

As ,
So ω scales as s-1 M0: unloaded mass
m: Mass change
M: Total mass
Sensitivity,

And it can be shown that S varies as s -4 .

For a 10X down scaling of dimensions, sensitivity increases 10000 times

!!!
 Why MEMS ?
SCALING OF PARAMETERS
Example : Capacitor (Electrical Parameters)

If the same electric field E = 108 V/m needs to be mainitained between the
plates of a micro sized capacitor and a macro sized capacitor, then

Voltage
Voltage = E x gap
Thus, voltage will scale as the gap between the plates. Therefore a much
smaller voltage will be required in the micro case to produce the same
effect.

+V
gap

gnd
 Scaling of Natural Forces

Force Scaling law

Surface tension S1

Electrostatic, Pressure S2

Magnetic S3

Gravitational S4

• Where s is a scaling factor,

• Means if the device dimensions are scaled s times, the effects of
surface tension are scaled s times, electrostatic force are
scaled s2 times and so on…
 Building Blocks
• Major components in MEMS systems include
– Design
• Much more difficult than IC designs due to the interdisciplinary character
of MEMS
• Design includes packaging
– Packaging is one of the most challenging step both in design and realization
• Transducers must be integrated with electronics
– Integration with ICs is another challenge for MEMS due to difficult issues of
process compatibility
– Fabrication
• Silicon technology is widely used in MEMS with new step added
– Dimensions are usually much larger than those in ICs even for nano-
transducers. To feel NANO you do not need to be in the nano-scale size!
– Other materials are included to perform required functions of transducers
• MEMS are frequently integrated with fluidics (polymers, glass…)
– Materials
• Materials that can perform required functions (thermo, piezo-, magneto-
resististance…)
• Interaction with fluidics (half-cell potential, corrosion…)
 IC & MEMS design paradigms

Process
Process/
Material

Device
Device

System/
Packaging
System/
Packaging

IC Design MEMS Design

High level design issues and their relation to
modeling and analysis
MEMS Multi-tiered Modeling & Simulation

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Physical

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Behavioral model
 Mechanical Structures Were Developed First
• Electromechanical MEMS sensors became very popular: beams, membranes,
hinges ….
– Advantages over macroscopic systems: sensitivity, miniaturization, low noise.
– Applications: pressure sensors, accelerometers, gyroscopes, micromirrors (digital
multimedia)
 Micromechanical Structures
• Micromirrors (>100k) in a Digital Light Processor by Texas Instruments the idea
came from etching experiments.
– Addressed individually using row-column multiplexing (SRAM in CMOS): Digital
Micromirrors (10x10µm2)
– Advantages: bright, high contrast, stability …
– Applications: image projection, optical communication and others maskless
lithography, DNA microarrays for light assisted synthesis.
Major MEMS Categories
 Micromechanical Structures
• Mechanical structures as electrical elements

Tunable capacitor & tunable inductor

 BioMEMS=Biological MEMS
• BioMEMS are used in biology, biophysics,
biochemistry, medicine, and pharmacy
• Mechanical structures: probes used in • Chemical/biochemical/biophysical:
vitro (testing) or in vivo (implanted for combined with fluidics
testing and/or stimulation)
 Communication from/to/within MEMS
• Traditional electrical signals
• Optical communication: microoptoelectromechanical systems
MOEMS (speed is important)
Optical signals switched traditionally
by optical/electrical/optical
(OEO) transformation:
1. Turning optical signals into electrical
using optical receiver arrays
2. Electronics signal processing
3. Transforming signals back to optical
domain

Or directly using optical switches

Includes optical
Elements and
interconnects
 Intrinsic Characteristics of MEMS
• Miniaturization: dimensions of MEMS structures are much larger than in
VLSI ICs (µm). Further scaling leads to NEMS (nano) that are
comparable/smaller than ICs (1-100 nm).
• Scaling laws describe how properties/behavior change with dimensions
– Scaling of spring constants (ex. behavior of cantilevers

E- Young modulus of elasticity; l, w, t - dimensions

3
Ewt
k= 3 l → L,w → L,t → L,C =  3
4l
Decreasing length of cantilever: smaller spring constant,
L4 higher resonance frequency (GHz) and quality factor
k =C L (50,000), better sensitivity
4 EL 3 
 – Scaling Law of Area-to-Volume Ratio area

L2 1
=
volume L3 L
(important in all surface effects: forces friction, tension, van der Waals etc)

– Microelectronics Integration - the most

widely used is that with CMOS
Scaling and Dimensions
Specifically important in Bio-applications
Devices: Sensors
and Actuators

Energy domains
and Transducers
 Sensors
• Fall into two categories:
– Physical: force, acceleration, pressure, temperaure, magnetic/electric field strength etc.
– Chemical/biological: pH, reactions, binding between molecules etc.
• Characteristics:
– Sensitivity
– Linearity
– Responsivity (large signal-to-noise ratio SNR required)
• Johnson noise, a with noise Vnoise = 4kTRB
,
thermal fluctuation, (k=Boltzmann’s constant, R=resistance, B=bandwidth), Gaussian distribution
• Shot noise (quantum fluctuation) Inoise = 2qIdc B
 noise,(conductance fluctuation when currents flow)
• 1/f noise or flicker (pink)
• Thermal-mechanical noise floor (mechanical motion of elements)
– SNR 
– Dynamic range (highest to lowest signals)
– Bandwidth (bandpass)
– Drift (degradation and change of operational points)
– Sensor reliability (related to stability of operation independently of conditions)
– Cross talk or interference (individually tested parameters should not be affected by other
measurements/signals)
– Development cost and time (vary depending on designs and technology, simulations are
very important in shortening the time-to market)
 Actuators
• Transform energy from/to the mechanical domain
into/from others: electrical (piezoelectricity,
electrostatic), thermal, magnetic etc.
 Design aspects of actuators
• Torque and force output capacity. Sufficient force must be delivered as a
response of the sensed phenomena.

• Range of motion. Should be adequate to the sensed phenomena.

• Dynamic response speed should be fast and bandwidth adequate.

• Ease of fabrication and availability of materials used for MEMS fabrication.

• Power consumption should be small (portable devices) and energy

efficiency high.

• Linearity of displacement as a function of driving bias.

• Cross-sensitivity and environmental stability.

• Footprint=total chip area. Arrays frequently used for complementary

measurements.
 MEMS Simulation Tools
S. No. Simulation Tool Description
1. Multiphysics Analysis System Level Simulation
2D Layout [CIF, GDSII, DXF]
Tool Fabrication
from ANSYS Process emulation
Multiphysics capabilities [3D solid model, Device Analysis, Behavioral model
extraction]
2. MEMS+, CoventorWare, MEMS and IC simulation together.
Architect3D, SEMulator 3D animation: mode shapes, time-harmonic behavior, and transient analysis.
from Coventor finite element analysis (FEA)
complex & real-world MEMS designs
Process modeling
3.
IntelliSuite MEMS layout design, advanced process simulation, FEA, parametric analysis,
from IntelliSense system simulation, packaging analysis, etc.
4.
MEMS Pro design and analysis of MEMS
From softMEMS mixed MEMS/IC schematic capture and simulation
3D model generation and visualization, behavioral model creation and links to
3D analysis packages
5. MEMS module Finite element modeling
from COMSOL
6. MEMSolver Multi-Physics analysis
from MEMS technology
solutions
7. SUGAR Based on Nodal analysis technique
from UC Berkeley
 Newer History
• Silicon micromachining started in 1980s:
– Bulk micromachining, which uses silicon substrate (more 3D structures)
such as in-jets (also for biological molecules

– surface, which uses thin

silicon films more 2D structures):
springs, gear trains, rotors…..
Intelligent/Smart Microsystem
 MEMS Products Examples

Product Category Examples

Pressure sensor Manifold pressure (MAP), tire pressure, blood pressure

Inertial sensor Accelerometer, gyroscope, crash sensor...

Microfluidics / Bio Inkjet printer nozzles, micro-bio-analysis systems, DNA

MEMS chips....Lab-on-chip or Micro-TAS

Optical MEMS / MOEMS Micro mirror array for projection (DLP)

Micro grating array for projection (GLV)
Optical fiber switches, adaptive optics....

RF MEMS High Q-inductors, switches, antenna, filter....

Others Relays, microphone, data storage, toys...

MEMS market forecast
 MEMS Products

An electrostatic micromotor An electrostatic comb drive actuator An electrostatic micromirror

MEMS Applications
THANKS