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)
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie2
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.
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie3
Transduction Mechanisms
Taken from Smith, R.L. “Sensors”, The Electrical Engineering Handbook, Ed. Richard C. Dorf, Boca Raton, CRC Press LLC, 2000
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie4
Transduction Mechanisms
Motorola’s integrated pressure sensor
Mechanical PiezoelectricityPiezoresistivity
Resistive, capacitive, and
inductive effects
Electrical
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie5
Transduction Mechanisms
JAMES S. HARRIS GROUP at Stanford University
Mechanical
Optical
Photoelasticsystems
(stress-inducedbirefringence)
InterferometersSagnac effectDoppler effect
Tunable VCSELs
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie6
Transduction Mechanisms
• 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
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie7
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
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie8
MEMS Transducer Systems
Separate componentsSignal attenuationNoisePackaging
Sensors
Actuators
Interface Circuits
Control and
Processing Circuits
Transducers
Power Supply and
Management
I/O Channel and Protocol
USER
OUTSIDE WORLD
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie9
MEMS Transducer Systems
Integrated sensors
Sensors
Actuators
Interface Circuits
Control and
Processing Circuits
Transducers
Power Supply and
Management
I/O Channel and Protocol
USER
OUTSIDE WORLD
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie10
MEMS Transducer Systems
Integrated microsystems
Sensors
Actuators
Interface Circuits
Control and
Processing Circuits
Transducers
Power Supply and
Management
I/O Channel and Protocol
USER
OUTSIDE WORLD
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie11
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
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie12
MEMS Design Process
Ref. Senturia, Microsystem Design, p. 18.
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie13
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
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie14
MEMS Design Methodology
Ref. Senturia, MicrosystemDesign, p. 23.
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie15
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)
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie16
MEMS Design Specifications (2)
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
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie17
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
MEMS Design Specifications (3)
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie18
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
∆∆
=
MEMS Design Specifications (4)
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie19
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)
MEMS Design Specifications (5)
EEL5225: Principles of MEMS Transducers 8/25/2004Lecture 2 by Xie20
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.