Microelectronic Systems
by
Oddvar Søråsen
NANO - nanoelectronics group
Department of Informatics
University of Oslo
2007
RF MEMS – new possibilities for future
wireless systems
Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
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MEMS as an extended activity of the NANO group
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Challenges by implementing a ”radio-on-a-chip”
Example:
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From MEMS devices to ”smart integrated systems”
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How to integrate CMOS and MEMS?
Examples:
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Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
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MEMS as an extended activity of the NANO group
z
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Challenges by implementing a ”radio-on-a-chip”
Example:
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From MEMS devices to ”smart integrated systems”
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How to integrate CMOS and MEMS?
Examples:
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Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
University of Oslo
M iFaculty
c r o e l e c t rof
onic Systems
Education
Faculty of
Social Sciences
Faculty of
Dentistry
Faculty of
Theology
Faculty of
Medicine
Faculty of Mathematics
and Natural Science
Faculty
of Arts
Faculty
of Law
2007
Institute of
Theoretical
Astrophysics
UoO: 30 000 students, 4600 employees
Department of
Geography
Department of
Informatics
School of
Pharmacy
Department of
Chemistry
Department
of Physics
Department of
Mathematics
Department of
Geophysics
Department of
Biology
Department of
Biochemistry
Microelectronic Systems
Ifi - main research directions
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Software Technology
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Distributed Systems
Information Systems
Microelectronic Systems
Computational Science
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Splines
Splines for geometry
and radiance rendering
2007
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Object orientation: SIMULA
Professors O.J.Dahl and
Kristen Nygaard:
von Neumann medal, Turing award
Commanders of St.Olaf Order
Microelectronic Systems
Who are we?
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Signal
processing
Programming
Microelectronic
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Systems
NANO has recently been
selected as ”Utviklingsmiljø”
by MNFak (5 years)
Vision: ”The Nanoelectronics
research group is to be
recognized as an international
top group within the field lowpower nano-/microelectronics
for wireless sensor networks”
Prizes for quality in education
and teaching environment
”Kunnskapsdepartementets
utdanningskvalitets pris 2006”
”Universitetets
læringsmiljøpris 2005”
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MEMS
Physics
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2007
”Nanoelectronics” (NANO) is
a research group within the
strategic area of
”Microelectronic Systems”
Microelectronic Systems
Members of the NANO group
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Faculties
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iDag T. Wisland (group
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Part time faculties/ researchers
iPhilipp Häfliger (100%)
iSnorre Aunet (100%)
iTor Fjeldly (UNIK) (20%)
iAlf Olsen (Micron) (20%)
iJoar M. Østby (SINTEF)
(20%)
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Engineers
iHåvard Kolle Riis
iHans K. O. Berge (33%)
2007
leader)
iYngvar Berg
iTor Sverre Lande
iOddvar Søråsen
Ph.D students
iJens Petter Abrahamsen
iHenning Gundersen
iHåkon A. Hjortland
iRene Jensen
iJohannes Lomsdalen
iJørgen Michaelsen
iOmid Mirmotahari
i3 in process
Microelectronic Systems
Research focus
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Developing systems based on
integrated electronics (VLSI)
full-custom design of analog,
digital and mixed-mode
circuits
prototyping and verification
Emphasizing low power
circuits
Future miniaturization
demands deep insight into the
technology
modeling non-ideal effects
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2007
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Microelectronic Systems
Research activities (1)
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Data conversion and sensor
interfacing
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Micro power digital signal
prosessering
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new circuit principles –
subthreshold operation
compact ultra low power CMOS –
redundancy – defect tolerance
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patent appl ”Birkeland Innovasjon”
Bio-inspired microelectronics
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nevromorph engineering
neural inspired microarchitectures
new ways of coding signals for
transmission
2007
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new principles for implementing
Delta-Sigma ADC, DAC
Microelectronic Systems
Research activities (2)
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Low power radio
communication
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Novelda AS
Combination of CMOS and
micro/nano-mechanics
(MEMS/NEMS)
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The research contains central
ingredients in implementing future
smart, integrated, wireless
sensor nods
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goal: develop a low power node
in a wireless sensor network
(WSN)
nanolectronics and sensors
RF front-end
integration: CMOS - MEMS
[JE]
2007
Ultra Wideband Impulse Radio
short range radar for medical
applications
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Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
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MEMS as an extended activity of the NANO group
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Challenges by implementing a ”radio-on-a-chip”
Example:
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From MEMS devices to ”smart integrated systems”
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How to integrate CMOS and MEMS?
Examples:
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Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
MEMS in electronic systems
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National initiative to establish micro and nano
technology in Norway
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MEMS a new degree of freedom to implement
integrated systems
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on sabattical leave 03/04
microelectronics can use micromechanical components
MEMS structures would need an electronic framework
Suitable competence at MES
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modeling, analysis, implementation of VLSI from transistors to
complex systems
2007
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Norwegian Research Counsel
MiNaLab in neighbouring building (SINTEF and UiO)
Microelectronic Systems
Selecting a focus Æ RF MEMS
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Challenging, promising and exciting field!
Close connection to circuit technique
An increasing number of applications of MEMS in RF
Large market: wireless communication
telecommunication, mobile phones
distributed intelligence (observation, activation)
environmental surveillance
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Consistent with IFI/MES strategic activity Æ Wireless Sensor
Nets
A new course established, 2005: INF5490 RF MEMS
2007
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”RF MEMS refers to the design and fabrication of dedicated
MEMS for RF (integrated) circuits”
Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
z
z
MEMS as an extended activity of the NANO group
z
z
Challenges by implementing a ”radio-on-a-chip”
Example:
z
z
From MEMS devices to ”smart integrated systems”
z
z
How to integrate CMOS and MEMS?
Examples:
z
z
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Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
Typical RF MES components
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Variable capacitors
Inductors
Resonators
Micromechanical filters
Phase shifters
2007
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Switches
Microelectronic Systems
Typical RF MES components
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Variable capacitors
Inductors
Resonators
Micromechanical filters
Phase shifters
2007
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Switches
Microelectronic Systems
Typical RF MES components
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Variable capacitors
Inductors
Resonators
Micromechanical filters
Phase shifters
2007
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Switches
Microelectronic Systems
Typical RF MES components
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Variable capacitors
Inductors
Resonators
Micromechanical filters
Phase shifters
2007
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Switches
Microelectronic Systems
Typical RF MES components
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Variable capacitors
2007
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Switches
Inductors
Resonators
Micromechanical filters
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Æ focusing on real
vibrating structures
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Can be used to implement
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Phase shifters
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oscillators
filters
mixer with filter
Æ
Microelectronic Systems
Comb resonator
2007
lateral movement
Microelectronic Systems
Beam resonator (clamped-clamped)
2007
vertical movement
Microelectronic Systems
Appealing advantages given by RF MEMS
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Higher performance
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Lower power dissipation
Lower cost
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batch processing
Circuit and system miniaturization
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monolithic integration with IC or by packaging!
2007
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increased selectivity
higher Q-factor
reduced loss
better isolation
low distortion
increased bandwidth
Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
z
z
MEMS as an extended activity of the NANO group
z
z
Challenges by implementing a ”radio-on-a-chip”
Example:
z
z
From MEMS devices to ”smart integrated systems”
z
z
How to integrate CMOS and MEMS?
Examples:
z
z
z
Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
Challenges by implementing transceivers
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Performance
todays RF systems need off-chip components to obtain required
performance
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matching networks, filters, oscillators etc.
Miniaturization
discrete components are a hinder
Reconfiguration
increased requirements to cover a variety of standards and channels
reconfigurable front-end for ”sw-defined radio” is needed
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RF MEMS components can be used as
A) Replacement for discrete passive components
B) New integrated functionality
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new system architectures
2007
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Microelectronic Systems
2007
Microelectronic Systems
2007
Itoh et al, fig 12.1
Microelectronic Systems
Overview of presentation
z
Department of Informatics and the NANO group
z
z
MEMS as an extended activity of the NANO group
z
z
Challenges by implementing a ”radio-on-a-chip”
Example:
z
z
From MEMS devices to ”smart integrated systems”
z
z
How to integrate CMOS and MEMS?
Examples:
z
z
z
Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
Master project (finished)
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Micromechanical filter by resonating beams
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Master student Ole-Petter Arhaug
Modeling
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Simulations with CoventorWare, Cadence
Design according to a specific process: QinetiQ
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analytical, FEM
QinetiQ INTEGRAM processes, a part of Europractice
O.-P. Arhaug and O. Søråsen, "Designing H-shaped Micromechanical
Filters", International MEMS Conference 2006, iMEMS2006, Singapore, 9 12 May, 2006. Journal of Physics: Conference Series, Institute of Physics
(IOP), (http://www.iop.org/EJ/journal/conf).
2007
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H structures
Microelectronic Systems
State-of-the-art tool for FEM analysis:
CoventorWare
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2) Partition the model (“meshing”)
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build by “stacking layers” (structural and sacrificial layers)
deposit layers - etch patterns - release
tetrahedrons, Manhatten bricks
3) Apply “solvers” on sub-elements
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electrical/ mechanical/ coupled
iterate
2007
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“Bottom-up” procedure:
1)Build a 3D model
Microelectronic Systems
Process specification
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Specify a process file which matches an actual foundry process
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simplifications
realistic: essential process features included
2007
Microelectronic Systems
Layout
2007
O-P Arhaug
Microelectronic Systems
3-D model building
2007
O-P Arhaug
Microelectronic Systems
Meshed 3D model for FEM analysis
2007
O-P Arhaug
Microelectronic Systems
Filter operation: 2 identical resonators
2007
In phase
Out of phase
Microelectronic Systems
2007
CoventorWare simulations for 6 resonating modes (O-P Arhaug)
Microelectronic Systems
Harmonic response for given dampings
2007
O-P Arhaug
Microelectronic Systems
Vision: Micromechanical signal processering
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Signal processing function implemented by
interconnection of MEMS resonators
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data is being processed in the frequency domain
2007
Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
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z
MEMS as an extended activity of the NANO group
z
z
Challenges by implementing a ”radio-on-a-chip”
Example:
z
z
From MEMS devices to ”smart integrated systems”
z
z
How to integrate CMOS and MEMS?
Examples:
z
z
z
Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
Combining MEMS and IC
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A strong demand exists for making combined MEMS – CMOS
systems
MEMS devices need surrounding µelectronics
2007
Microelectronic Systems
µelectronic systems can be
extended with MEMS devices
for contacting the environment
2007
Microelectronic Systems
How can µelectronics and MEMS be combined?
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Multi-chip
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combination of quite diverse technologies
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optimal processing of sub-modules
Si, glass, plastic, organic
heavy load impedances, parasitics
costly, work intensive
2007
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traditional method: SiP, SoP
separate, different processing lines involved
Microelectronic Systems
The ultimate goal
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SoC – System-on-Chip
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Æ Cheaper and more standardized procedures and
processes are needed!
2007
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easier handling
lower production costs
reduced parasitics
higher reliability
equal or higher performance!?
Microelectronic Systems
Typical features
MEMS features
a diversity of different processing
lines exist
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designers with background in
physics, material technology,
chemistry
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•
special features and secrets
limited interoperability
CMOS features
standardized processes
design activity and
semiconductor processing is
separated
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foundry concept, second sourcing
have expanded the design
community
working close to MEMS labs
Future MEMS/CMOS designers
− Designers with background in computer science, ASIC design
− Working on a conceptual level, separated from processing details
− Handling geometries
2007
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Microelectronic Systems
Methods for on-chip integration
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pre-CMOS
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intermediate-CMOS
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Mixed MEMS/CMOS
post-CMOS
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CMOS before MEMS
2007
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MEMS before CMOS
Microelectronic Systems
Methods for on-chip integration
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pre-CMOS
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Coars-grained MEMS steps introduce topographic variations
on the wafer surface
Æ Planarization before CMOS processing
Reluctance to take ”dirty” wafers into CMOS process lines
2007
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MEMS processing is done first
Microelectronic Systems
2007
Microelectronic Systems
Methods, cont.
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intermediate-CMOS
Certain steps in the CMOS process are modified
Intertwined process which hinders optimization of each
”processing module” separately
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2007
BiMOSII combination process from Analog Devices used for
implementing accelerometers
Microelectronic Systems
Methods, cont.
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post-CMOS
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High temperature can destroy the CMOS metallization
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Use special CMOS metal layers (e.g. tungsten) to withstand high
temperature
Use lower temperature when depositing structural MEMS materials
i Specific structural materials can be used, SiGe
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Generally, a whole wafer must be post-processed
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Different dimensions in MEMS and CMOS processing lines
Post processing single chips is not practical if masking is needed
2007
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An ordinary CMOS process is used first
MEMS processing steps are added
Microelectronic Systems
2007
MICS-prosess
Microelectronic Systems
2007
Microelectronic Systems
General observations
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Each of the combination methods
Limited in versatility and dissemination
Processing ”modules” would need a lot of investments for each new
upgrade
Æ It is striking to observe the enormous investments in the IC
industry for developing standardized and powerful CMOS processes
with still finer line dimensions and higher speed
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Why not using an ordinary CMOS process: CMOS – MEMS?
One way of implementing CMOS – MEMS
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ASIMPS run by CMP (”Circuits Multi-Projets”)
ST Microelectronics, ST7RF BiCMOS, 0.25µm
Postprocessing at Carnegie Mellon University (CMU)
A CMOS – MEMS test circuit has been developed at the NANO
group
Jan Erik Ramstad: CMOS – MEMS oscillator
Jostein Ekre: CMOS – MEMS inductors
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2007
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Microelectronic Systems
2007
ASIMPS
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Standard CMOS is used
MEMS structures: Multilayer stack of
metals and dielectrics
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MEMS devices released in a mask-less
etch & release process
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reduced Youngs modulus (E =
stiffness)
not so good material as
polySi/poydiamond used in specialized
MEMS processes
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Metal layer used as mask
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5 metal layers
any one can be used as a mask
defining the thickness of the
mechanical structure
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high aspect ratio RIE + isotropic etch of
underlying substrate
done chip-wise on individual diced
chips
no extra masks needed for MEMS Æ
MPW can be used
active CMOS circuit area must be
completely covered by metal
Specific MEMS design rules
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determine released or anchored areas
[CMU]
2007
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Microelectronic Systems
Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
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z
MEMS as an extended activity of the NANO group
z
z
Challenges by implementing a ”radio-on-a-chip”
Example:
z
z
From MEMS devices to ”smart integrated systems”
z
z
How to integrate CMOS and MEMS?
Examples:
z
z
z
Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
Master project (finished)
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Integrated MEMS/CMOS oscillator
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Master student Jan Erik Ramstad (Bachelor HiVe)
MEMS resonator with CMOS feedback amplifier
To be used as a ”resonant detector”
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a mechanical resonating structure where physical
measurement parameters modify the resonant frequency
e.g. sensing acceleration
Investigate possibilities for monolithic integration
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post CMOS micromachining Æ
2007
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based on a resonating cantilever beam
Microelectronic Systems
Cantilever beam
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Principle of operation
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2007
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The beam is attracted by
the electrostatic forces
between the electrode
and beam
A DC voltage over the
gap amplifies the el-mech
coupling
Contributions off the
fundametal frequency can
be omitted
[JER]
Equivalent diagram of the cantilever beam
k, m, b Æ C, L, R
Microelectronic Systems
Design example
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A CMOS – MEMS oscillator
Blockdiagram
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2007
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vibrating cantilever beam
coupled in loop with a
feedback Pierce CMOS
amplifier
oscillation at a frequency
given by the characteristic
resonating mode of the
cantilever beam modified by
the input and output
capacitances of the Pierce
amplifier
[JER]
Microelectronic Systems
Vibrating beam used as a sensor
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External acceleration will
bend the beam
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Beam layout
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laminated structure of 4 Al
alyers + SiO2
4.8 µm thickness (W) x 2 µm
width (H)
length = 100 (60) µm, gap =
1.2 µm
2007
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the spring coefficient of the
beam is slightly altered
the frequency is changed and
can be observed
Microelectronic Systems
Oscillation criterion
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”Motional resistance” of the beam, Rx
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A critical parameter
Dependent of the gap and overlap area for
electrostatic actuation
A low Rx is desirable
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2007
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small gap! – dependent on processing resolution and
polymer coating
large overlap area – thickness is limited by the laminated
structure
Rx ~ 700 kohm
”Barkhausen criterion”
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The negative input resistance Re(Zc) must be at
least 3x larger than Rx for oscillation to start up (by
thermal noise!)
The negative resistance is controlled by tuning the
Pierce capacitors C1, C2, gm and feedback
resistor
Re(Zc) will change during startup and will stabilize
when Rx and Re(Zc) become equal
Rx
Zc
Microelectronic Systems
Design parameters - layout
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Layout
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the gap of the cantilever beam must
have a DC voltage across
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The design has been modeled and
simulated
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3 designs (frequencies 120, 150, 480 kHz)
2007
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introduced by a resistor and coupling
capacitance (one-port structure)
(a two-port structure: decreased resolution)
Test circuit
Microelectronic Systems
2007
Sent to production
in January 2007
[JER]
Microelectronic Systems
2007
Poster at DTIP 2007
Design, Test, Integration and
Packaging of MEMS/MOEMS,
25-27 April 2007, Stresa,
Lago Maggiore, Italy
Microelectronic Systems
Master project (finished)
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RF transceiver for a Wireless Sensor Node
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Medical application
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Built-in intelligence
Robust
Low-power
Master student Jostein Ekre
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Design and demonstration of critical RF MEMS parts
Interfacing and implementation issues
2007
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Brain pressure sensor
Microelectronic Systems
MEMS inductors
are vital for
implementing
WSNodes
2007
Planar coils made from
multiple metal layers
Transmitter
[Jostein Ekre]
Microelectronic Systems
The same test circuit did also contain MEMS inductors
2007
[JE]
Microelectronic Systems
Ex. from CMU: ”C, L resonator tank”
2007
Microelectronic Systems
Overview of presentation
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Department of Informatics and the NANO group
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z
MEMS as an extended activity of the NANO group
z
z
Challenges by implementing a ”radio-on-a-chip”
Example:
z
z
From MEMS devices to ”smart integrated systems”
z
z
How to integrate CMOS and MEMS?
Examples:
z
z
z
Filter based on resonating mechanical structures
CMOS – MEMS monolithic oscillator
CMOS – MEMS inductors
Future plans
2007
What is RF MEMS?
Microelectronic Systems
The future: ”From devices Æ systems”
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Future smart systems would require combination of
technologies
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The ASIMPS method could be one way for a group of
applications
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using ”many”, ”non-optimal” MEMS devices
effective interfacing to electronics
Æ high performance systems
enhanced performance due to process upgrading
2007
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e.g. integrated CMOS – MEMS systems
Micro og nano sensors integrated with complex electronics
will be used in distributed, ubiquitous systems, medical
implants etc.
Microelectronic Systems
Activities
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SINTEF project
CMOS – MEMS at MiNaLAB
part of SIP
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2007
Microelectronic Systems
2007
SINTEF
Thor Bakke
J.E. Ramstad
Microelectronic Systems
Activities
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SINTEF project
CMOS – MEMS at MiNaLAB
part of SIP
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New Master project: Combination of microelectronics (CMOS) og
miniatyrized mechanical components (RF MEMS) for reconfigurable ”radioon-a-chip front-end”
varactor (variable reactor) is central for reconfigurability
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VCO (voltage controlled oscillator)
designing for maximum tuning range and high performance
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New Ph.D. project: Micromachined RF front-end modules integrated with
standard CMOS microelectronics in smart wireless sensor networks
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RF MEMS resonating CMOS – MEMS structures
2007
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Microelectronic Systems
Personal research goals
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2) Investigating effective methods for integration of the
MEMS with microelectronic subsystems, preferably as a
monolithic Si chip (SoC)
Æ Critical technology and realistic implementations of
Wireless Sensor Nodes
2007
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1) Designing RF MEMS and investigating how to use
high performance micromechanical replacement parts in
RF systems instead of todays bulky and power
consuming off-chip components