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EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie1

Sensor and Actuator Technology

Agenda:ClassificationTransduction MechanismsMEMS SystemMEMS Design Methodology MEMS Design Specifications

Reading: Senturia, Ch. 2 pp. 15-28.

EEL5225: Principles of MEMS Transducers (Fall 2004)


Classification

TransducerElement that converts one form of energy to another.May include

– sensors (for measurement)– actuators (for doing work)– displays

Microsensor or microactuator a sensor or actuator that is manufactured using microfabricationand micromachining techniques

Other microstructures that neither sense nor actuate.Microchannels, micronozzles, microlenses, etc.


Transduction Mechanisms

Taken from Smith, R.L. “Sensors”, The Electrical Engineering Handbook, Ed. Richard C. Dorf, Boca Raton, CRC Press LLC, 2000



Motorola’s integrated pressure sensor

Mechanical PiezoelectricityPiezoresistivity

Resistive, capacitive, and

inductive effects

Electrical



JAMES S. HARRIS GROUP at Stanford University

Mechanical

Optical

Photoelasticsystems

(stress-inducedbirefringence)

InterferometersSagnac effectDoppler effect

Tunable VCSELs



• Xie’s group at University of Florida

ThermalThermal expansion

(bimetal strip, liquid-and gas thermometers,

resonant frequency)Radiometer effect

(light mill)

Mechanical

oxide

siliconsubstrate

metal

poly-Sisilicon

mirror

Bimorphactuator

x

z

Cross-sectional View

bimorph actuator

mirror

mirrorbimorph actuators

1mmframe


MEMS Transducer Systems

Modular MEMS system designSensor designActuator designInterface designPackaging design

Sensors

Actuators

Interface Circuits

Control and

Processing Circuits

Transducers

Power Supply and

Management

I/O Channel and Protocol

USER

OUTSIDE WORLD



Separate componentsSignal attenuationNoisePackaging

Sensors

Actuators

Interface Circuits

Control and

Processing Circuits

Transducers

Power Supply and

Management


USER

OUTSIDE WORLD



Integrated sensors

Sensors

Actuators

Interface Circuits

Control and

Processing Circuits

Transducers

Power Supply and

Management


USER

OUTSIDE WORLD



Integrated microsystems

Sensors

Actuators

Interface Circuits

Control and

Processing Circuits

Transducers

Power Supply and

Management


USER

OUTSIDE WORLD


MEMS Design Strategy

High-Level Design IssuesMarket, Impact, Competition, Technology, Manufacturing

Ref. Senturia, Microsystem Design, p. 18.

Technology-driven or market-driven?

+++++++++++++++Commercial Products

++++++++++Research Tools+++++

Technology Demonstration

ManufacturingTechnologyCompetitionImpactMarketsCategory

Relative Importance of High-Level Design Issues


MEMS Design Process

Ref. Senturia, Microsystem Design, p. 18.


MEMS Design Methodology

Top-down designSystem levelDevice: macromodelsPhysical: numerical modeling, finite-element methodsProcess: TCAD or Technology CAD

Bottom-up verification

System

Device

System

Device

Simulation

Verif

icat

ion


MEMS Design Methodology

Ref. Senturia, MicrosystemDesign, p. 23.


Definitions: P(t) = physical variable (input)x(t) = sensor excitationy(t) = sensor response (output)

Sensor Interface Circuit Data System

P(t) y(t)

x(t)

Pmeas.(t)

Disturbances

Calibrationdetermines the function that relates y(t) to known physical input, P(t)

Pmeas.(t) = P(t) ?

MEMS Design Specifications (1)



Full Scale Outputalgebraic difference between upper and lower endpoints of output

Linearitycloseness of calibration curve to a specified straight line (maximum deviation of calibration point from straight line as percentage of Full Scale Output)

Offsety(t) under normal excitation and zero applied input, P(t)=0

y(t)

P(t)

offset

Full scale outputS


Hysteresismaximum difference in y(t) when the value is approached first with increasing input and second with decreasing input, expressed in percent Full Scale Output

Errordifference between measured P(t) and true value of P(t) (usually indicated as percentage of Full Scale Output)

y(t)

P(t)

Hysteresis



Sensitivitymagnitude of change of y(t) with respect to change in P(t),

Accuracyratio of Error to Full Scale Output expressed in percentage

Repeatabilityagreement between independent measurements made under the identical conditions (maximum difference in output readings given as % of Full Scale Output)

Resolutionsmallest change in P(t) that results in a detectable change in y(t)(called Threshold if increment is from zero)

Frequency Responsechange with frequency, ω=2πf , of output/input magnitude ratio and phase difference for sinusoidally varying input

)()(

tPtyS

∆∆

=



Cross-axis sensitivitysensitivity of sensor to transverse acceleration or other transverse input (also known as transverse sensitivity)

Signal-to-NoiseS/N = y/nrms where y is the output magnitude and nrms is the root-mean-square noise

Selectivityability to measure one input (measurand) in the presence of other inputs

Overload characteristicsmaximum magnitude of input that can be applied to the sensor without changing the sensor response

Stabilityability of sensor to reproduce output for identical input and conditions over time (expressed as percent of Full Scale Output)



Homework 1Due: Wednesday , September 1

Problem 1.1 (Textbook)A Library Treasure Hunt: By consulting recent issues of at least two of the following MEMS-oriented journals, locate articles that illustrate (a) accelerometers for human activity monitoring or civil infrastructure security, (b) MEMS optical imaging, (c) MEMS optical switching, (d) MEMS biosensors, (e) RF MEMS, and (f) MEMS microphones. The journals are: IEEE/ASME Journal of Microelectromechanical Systems, Journal of Micromechanics and Microengineering, Sensors and Actuators, Sensors and Materials, IEEE Sensors Journal, and Biomedical Microdevices. Give full citations of at least two articles for each of the above topics. List the top 2 topics that are most interesting to you. Note: The Marston Science Library has the IEEE/ASME Journal of Microelectromechanical Systems, Sensors and Actuators A: Physical and B: Chemical (hardcopy and electronic), Analytical Chemistry, and Biomedical Microdevices (electronic copy). Also, make sure to take advantage of IEEE Explore.

Problem 1.2 (Textbook)An On-Line Treasure Hunt: By consulting the events calendar at the web site http://www.memsnet.org (or some other MEMS-oriented web site), identify conferences scheduled for the coming year that cover some combination of (a) accelerometers for human activity monitoring or civil infrastructure security, (b) MEMS optical imaging, (c) MEMS optical switching, (d) MEMS biosensors, (e) RF MEMS, and (f) MEMS microphones.

sensor and actuator technology - · pdf file1 eel5225: principles of mems transducers lecture...

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