mary coan april 6 th 2010. outline how it all began… nanoelectromechanical systems (nems) basic...
TRANSCRIPT
Outline
How it all began…Nanoelectromechanical Systems (NEMS)
Basic Properties Typical Problems Fabrication Processes Application of NEMS Conclusion
How it all began… 1959-Richard Feynman offered a prize of $1000 "to the first guy who makes
an operating electric motor - a rotating electric motor which can be
controlled from the outside and, not counting the lead-in wires, in only 1/64
inch cube."
stimulate new fabrication technology
1960-Bill McLellan, using amateur radio skills, built the motor with his hands
using tweezers and a microscope
2000 rpm motor weighed 250 micrograms
13 parts
http://www.nanowerk.com/spotlight/spotid=2431.phpImage 1: http://nano.caltech.edu/gallery/group2.html
Nanochamber - ultrafast gas sensing with NEMS resonators
Nanoelectromechanical Systems (NEMS) In the 50 years since-
The field of microelectromechanical systems (MEMS) caught up with Feynman's bet
achieved commercial production capabilities of motors many times smaller
NEMSdevices integrating electrical and mechanical
functionality on the nanoscale Research on building functional nanoscale
electromechanical systems is well underway
http://www.svtii.com/files/MEMS-NEMS-SVTI.pdfImage 1: http://nano.caltech.edu/gallery/group2.html
Colorized SEM image of Ultra High Fequency NEMS resonator
Nanoelectromechanical Systems (NEMS) Used in aerospace, automotive, biotechnology,
instrumentation, robotics, manufacturing and other applications
Many functionsSensingActuation Communication
http://www.svtii.com/files/MEMS-NEMS-SVTI.pdfImage 1&2: http://nano.caltech.edu/gallery/group2.html http://www.kschwabresearch.com/articles/detail/11
SEM - nanocantilever resonator gas sensor
SEM image of two Single Cell Pico Force Microscopy force sensors
Nanomechanics coupled to superconducting microwave resonators
Outline
How it all began…Nanoelectromechanical Systems (NEMS)
Basic Properties Typical Problems Fabrication Processes Application of NEMS Conclusion
Basic Properties Two principal components common to most
electromechanical systemsMechanical element
○ Either deflects or vibrates in response to an applied force○ Used to sense static or time-varying forces
Transducers○ Convert mechanical energy into electrical or optical signals
and vice versa○ Input transducer simply keeps the mechanical element
vibrating steadily while its characteristics are monitored as the system is perturbed
http://www.nanowerk.com/spotlight/spotid=2431.phpImage 1: http://palasantzas.fmns.rug.nl/NEMS.html
Basic Properties Attain extremely high fundamental frequencies
mechanical responsitvity Dissipate very little energy
Characterized by the high quality or Q factor of resonance
Extremely sensitive to external damping mechanismsCrucial for building many types
of sensorsSuppression of random
mechanical fluctuations○ Highly sensitive to applied forceshttp://www.nanowerk.com/spotlight/spotid=2431.php
http://palasantzas.fmns.rug.nl/NEMS.html Image1: http://phycomp.technion.ac.il/~phr76ja/boston/what2.html
Outline
How it all began…Nanoelectromechanical Systems (NEMS)
Basic Properties Typical Problems Fabrication Processes Application of NEMS Conclusion
Typical Problems Great promise as highly
sensitive detectors mass, displacement, charge,
and energy An efficient, integrated, and customizable
technique for actively driving and tuning NEMS resonators has remained elusive
Electromechanical devices are scaled downward transduction becomes increasingly difficult
○ Causing the creation of finely controlled integrated systems to fail
http://www.nanowerk.com/spotlight/spotid=2431.php Image1: http://phycomp.technion.ac.il/~phr76ja/boston/what2.html
Typical Problems Resonator sizes continue to decrease to the
nano-scaleSurface to volume ratio increases
○ Susceptible to a variety of surface related noise mechanismsSuch as gas molecules impinging the surface, loss due to
defects and impurities, scattering of surface acoustic waves by roughness
Surfaces contribute the most to energy dissipation in NEMSdetailed understanding is still missing
http://www.nanowerk.com/spotlight/spotid=2431.php http://www.gizmag.com/nanoscale-light-resonator/13401/picture/105479/ Image 1
Nanoscale resonators exert relatively strong forces on tiny particles, leading the way to important advancements in
MEMS and MOMS systems
Typical Problems Casimir Effect
quantum mechanical force that attracts objects a few nanometers apart
Very Strong Force○ Hard to control
devices Efficient actuation
creation of mechanical
motion by converting
various forms of energy
rotating or linear
mechanical energyhttp://www.semiconductor.net/article/444199-Scientists_to_Conquer_Casimir_Effect_Enable_NEMS.php
MEMS setup used to detect the presence of Casimir force.
Typical Problems Fabrication
Scale down effects○ Lithography
Wave length limitations
Integration with typical CMOS processes Mass Production
Packaging ○ Fragile
Cost
Top Image: http://www.texmems.org/ Bottom Image: http://www.nems.se/nimble.html
Outline
How it all began…Nanoelectromechanical Systems (NEMS)
Basic Properties Typical Problems Fabrication Processes Application of NEMS Conclusion
Fabrication Processes Basic Steps of Silicon Micromachining:
LithographyDeposition of sacrificial and structural layers (PECVD,
evaporation, sputtering)Removal of Material (patterning)Selective etching (RIE, Laser)DopingBonding (Fusion, anodic)Planarization
MEMS and NEMS: systems, devices, and structures Nano- and microscience, engineering, technology, and medicine series By: Sergey Edward LyshevskiImage: http://hello-engineers.blogspot.com/2009/04/mems-fabrication-assembling-and-packing.html
Fabrication Processes
Surface Micromachining and sacrificial layer technique
Animated Version
http://iopscience.iop.org/0964-1726/10/6/301/pdf/sm1601.pdf?ejredirect=migration
Substrate (Silicon Wafer)
Sacrificial Layer (SiO2)
Photo Resist
MaskMask
UV Light
Photo Resist
Photo Resist
Sacrificial Layer
Fabrication Processes
Bulk Micromachining along crystallographic planes
Animated Version
http://iopscience.iop.org/0964-1726/10/6/301/pdf/sm1601.pdf?ejredirect=migration
(100) Silicon Wafer P+ Si
Photo Resist
SiNx
UV Light
Fabrication Processes
Left image: http://www.memx.com/ Right Image: http://www.npl.co.uk/science-+-technology/nanoscience/surface-+-nanoanalysis/mems-particle-detector
Outline
How it all began…Nanoelectromechanical Systems (NEMS)
Basic Properties Typical Problems Fabrication Processes Application of NEMS Conclusion
Application of NEMS:NEM switched Capacitor
Demand for increased information storagePushed silicon technology to its limitsResearch involving novel materials and device
structures○ Magnetoresistive random access memory ○ Carbon nanotube field-effect transistors
NEM switched capacitor structureVertically aligned multiwalled carbon nanotubes
○ mechanical movement of a nanotube relative to a carbon nanotube based capacitor defines ‘ON’ and ‘OFF’ states
Impossible to control the number and spatial location of nanotubes over large areas
JAE EUN JANG, et. al . “Nanoscale memory cell based on a nanoelectromechanical switched capacitor” Nature Vol 3 January 2008 doi:10.1038/nnano.2007.417
Application of NEMS:NEM switched Capacitor
Carbon Nanotube Fabrication:Grown with controlled dimensions at pre-defined
locations on a silicon substrate○ Compatible with existing silicon technology○ Vertical orientation allows for a significant decrease in cell
area over conventional devices
JAE EUN JANG, et. al . “Nanoscale memory cell based on a nanoelectromechanical switched capacitor” Nature Vol 3 January 2008 doi:10.1038/nnano.2007.417
Application of NEMS:NEM switched Capacitor
JAE EUN JANG, et. al . “Nanoscale memory cell based on a nanoelectromechanical switched capacitor” Nature Vol 3 January 2008 doi:10.1038/nnano.2007.417
Application of NEMS:NEM switched Capacitor Data has been written to the structure
Theoretically it is possible to read data with standard dynamic random access memory sensing circuitry
Simulations have been completedhigh-k dielectrics instead of SiNx
○ increase the capacitance to the levels needed for dynamic random access memory applications
JAE EUN JANG, et. al . “Nanoscale memory cell based on a nanoelectromechanical switched capacitor” Nature Vol 3 January 2008 doi:10.1038/nnano.2007.417
Application of NEMS:Self Sustaining NEM oscillator
Sensors based on nanoelectromechanical systems vibrating at high and ultrahigh frequencies capable of levels of performance that surpass those of larger
sensors NEM devices have achieved unprecedented sensitivity
Displacement, mass, force and charge detection Passive devices
Require external periodic or impulsive stimuli to excite them into resonance
Novel autonomous and self-sustaining NEM oscillatorGenerates continuous ultrahigh-frequency signals when
powered by a steady d.c. source
X.L. Feng, et.al. “A Self Sustaining Ultrahigh-frequency nanoelectromechanical oscillator” Nature Vol 3 June 2008 doi:10.1038/nnano.2008.125
Application of NEMS:Self Sustaining NEM oscillator
A self-sustaining ultra high frequency NEM oscillatorFrequency determining element in the oscillator is a
NEM resonator○ Embedded within a tunable electrical feedback network to
generate active and stable self-oscillationExcellent frequency stabilityLinewidth narrowing and low phase noise performance
X.L. Feng, et.al. “A Self Sustaining Ultrahigh-frequency nanoelectromechanical oscillator” Nature Vol 3 June 2008 doi:10.1038/nnano.2008.125
Application of NEMS:Self Sustaining NEM oscillator
X.L. Feng, et.al. “A Self Sustaining Ultrahigh-frequency nanoelectromechanical oscillator” Nature Vol 3 June 2008 doi:10.1038/nnano.2008.125
Dc=source voltage to increase the ac current volatageAmplifier is amplifing the voltage from the phase controlled current The resonator is filtering the current, allowing for only a certain freq to go throughH(jw) is a freq responseControl changes the phase
Application of NEMS:Self Sustaining NEM oscillator
Ultrahighfrequency oscillators provide a comparatively simple means for implementing a wide variety of practical sensing applications
Opportunities for nanomechanical frequency control, timing and synchronization
X.L. Feng, et.al. “A Self Sustaining Ultrahigh-frequency nanoelectromechanical oscillator” Nature Vol 3 June 2008 doi:10.1038/nnano.2008.125
Application of NEMS:NEM Tunable Laser
Tuning the frequency of an oscillator is of critical importanceFundamental building block for many systems
○ Mechanical or Electronic
Highly inadequate in optical oscillatorsParticularly in semiconductor laser diodes
Limitations in tuning a laser frequency (or wavelength)include the tuning range and the speed of tuning
○ Typically milliseconds or slower
Tuning is often not continuousRequires complex synchronization of several electrical control
signalsM.C.Y. Huang et.al “A Nanoelectromechanical tunable laser” Nature Vol 2 March 2008 doi:10.1038/nphoton.2008.3
Application of NEMS:NEM Tunable Laser
Nanoelectromechanical Tunable LaserLightweight NEM mirror based on a single-layer, high
contrast grating (HCG)○ Enables a drastic reduction of the mirror mass○ Increases the mechanical resonant frequency ○ Increases the tuning speed
Allows a wavelength-tunable light source ○ Potential switching speeds of the order of tens of
nanoseconds○ Various new areas of practical application
bio- or chemical sensing, chip-scale atomic clocks and projection displays
M.C.Y. Huang et.al “A Nanoelectromechanical tunable laser” Nature Vol 2 March 2008 doi:10.1038/nphoton.2008.3
Application of NEMS:NEM Tunable Laser
M.C.Y. Huang et.al “A Nanoelectromechanical tunable laser” Nature Vol 2 March 2008 doi:10.1038/nphoton.2008.3
Schematic of the electrostatic-actuated NEMO-tunable VCSEL
High Contrast Grating (HCG) is freely suspended above a variable air gapSupported by a
nanomechanical structure○ cantilever○ Bridge○ folded beam ○ membrane
Application of NEMS:NEM Tunable Laser
Integration of the freely suspended HCG mirror with a variety of nanomechanical actuators that can be designed for different values of mechanical stiffness
M.C.Y. Huang et.al “A Nanoelectromechanical tunable laser” Nature Vol 2 March 2008 doi:10.1038/nphoton.2008.3
Application of NEMS:NEM Tunable Laser
Wavelength tuning is a function of the air-gap thickness below the NEM suspended HCG
Blue Triangle Curves Calculated laser emission
wavelength (Wavelength) Color-coded Contour
HCG mirror reflection bandwidth (Reflectivity)
M.C.Y. Huang et.al “A Nanoelectromechanical tunable laser” Nature Vol 2 March 2008 doi:10.1038/nphoton.2008.3
Outline
How it all began…Nanoelectromechanical Systems (NEMS)
Basic Properties Typical Problems Fabrication Processes Application of NEMS Conclusion
Conclusion Nanoelectromechanical systems (NEMS) are used to
measure extremely small masses and forces Measurements rely on a resonator oscillating at a very
stable frequency so that a small change in the resonant frequency caused by, for example, a molecule landing on the resonator, can be readily detected
Self-sustaining NEMS oscillators enable a wide spectrum of applicationsOffer significant advantage over other frequency-shift detection
as no source of external excitation is requiredYields an immense simplification of design that is crucial for
next-generation, highly multiplexed sensing applications involving large arrays of devices
Conclusion A viable structure and fabrication process for a NEM memory
cell for ultra-large-scale integrated memory applicationsProposed write–read scheme is similar to that of a conventional
DRAM○ Conventional sensing schemes○ CMOS circuits ○ High integration densities due to the vertical nature of the NEM
capacitor
High-speed nanoelectromechanical tunable laser Monolithically integrating a lightweight, single-layer HCG as the
movable top mirrorresults in a drastic reduction in mass substantial improvement in tuning speedResults in an optical mirror design for the next generation of NEMO-
tunable devices
Rebuttal• There were several comments on the lack of information
regarding the physics behind how NEMs work– I chose not to go into great depth about the physics behind
these devices due to the audience• I understand that there are graduates in the class however the
majority of the class are undergraduates who have never been in contact with this subject matter before
– An example of how the mechanical process of the device worked using an animation would have been helpful
– An overview of the current technology (MEMS) may also have been added
• I left out certain information regarding the process of some of the example covered due to the time constraints and the level of expertise needed to fully understand
Rebuttal
• In regards to the organization of the presentation, NEMS is a very broad topic with many different applications, processes (new and old) and types devices due to time constraints I could not mention all of the information– I chose to keep the presentation simple for the sake of the
majority of the audience– I understand that the graduates in the class may have prior
knowledge of NEMS and such a simplified presentation may not be enough information for them
• I believe I spoke about the different applications of the sensors in class and showed images of them throughout the presentation
Rebuttal• I am not sure how the cantilever beam was not well
depicted– There was an example of how to form a cantilever beam– I did not go to into detail about the cantilever beam because
it is an older technology and I was trying to focus on newer NEMS technologies
• In regards to NEMS “wearing out” and stiction problem, they do. Different types of materials are being looked into to help with this problem.
• As of today NEMS, as far as I know, NEMS are not massively produces like Si based chips because of the variation issues. – They are produced on smaller sized wafers instead of the
larger ones to help with this issue
Rebuttal
• Thank you for all of the comments I will try to take them into account for future presentations I have to give.
The presenter explained some of the basic concepts related to NEMS in general terms. However, she did not explain the physics behind those process that would have been helpful to understand how the transducer and the mechanical works. She explain some of the problems of this technology but the explanation of the Casimir effect was not clear. She mention some fabrication process and explain one process.
The paper about NEM switched Capacitor was very interesting. However, some of the details about the fabrication were not clear for instance how they position the carbon nanotubes? and how they do the SiN coating? Was it by e-beam lithography? Open questions about the paper are: how easily is to reproduce the results of the device? and is it possible to achieve large scale integration of these devices?
http://cdn.physorg.com/newman/gfx/news/hires/khatibmems.png
The paper about NEM Tunable Laser looks interesting but she did not explain clearly how the device works. She showed the capabilities of the device and the design and images of the device. However she did not explain which role play the different parts of the device.As further research, I consider that work in large scale integration of NEMS is needed. Also research in bio-NEMS for uses in disease diagnosis and biological weapon sensor. http://www.boulder.nist.gov/div853/MRD_Groups/MRD_Projects/
BioMEMS_cell_puller.jpg
NEMS lecture review
The theme was not well organized. It should have been emphasized the different novel methods enabling NEMS development, i.e. laser micromachining for 3D structures,DRIE for high aspect ratio structures, soft lithography for biocompatible devices, etc.
The essence of different working principles used for NEMS sensors and actuators should have been mentioned, i.e. thermal, electrical, piezolectric, piezoresistive, magnetic and electrostatic.
Essential electrical and mechanical concepts such as stress & strain and resonant frequency & quality factor were not illustrated.
The cantilever beam was not correctly illustrated when it was mentioned on applicationsfor chemical sensing or mass spectrometry, it was not explained what factors contributeto getting a high sensitivity to mass or pressure.
The cantilever beam is the basic element for a broad range of applications and its basic working principle was neither well depicted.
Alfredo D. Bobadilla
Nano-electro-mechanical Systems
• Nanoscale size
Berkeley Lab (www.lbl.gov)
The logic reduction-sizie step on microelectronical devices
Features
• Transduction of a mechanical stimuli into a signal
• Two basic elements: a) Mechanical part b) Transductor
In the example above, the nanotube is connected to an electrode. The nanotube is made vibrate at certain frequency, but this changes as atoms impinge onto the nanotube. The change in frequency is converted in an electrical signal that relates to the weight of detected atoms
Review
• There was a good amount of graphics and information in the slides. The animation made for the fabrication process was very good
• A fairly number of applications and examples was shown, corresponding to several recent (2008-present) high-impact publications
• The speaker looked confident, coherent, and in general made a good oral presentation
Review• Perhaps, the execution of the introduction could improve.
Although, I realize the ‘Basics’ sections is present, there is certain elements that would have deserved more emphasis:
a) The working (elementary) principle of the NEMS in sensing, actuation and communication.
b) An overview to the current technology (MEMS). It would be easier to understand the goals of NEMS, if one understands how the currently technology works in several applications
• The ‘history’ slides that open the presentation rises the expectation of a talk about nano-sized motors, but the topic covered is more of mechanical responses converted in signals. A more suited example should be used to open up
Nanoelectromechanical Devices, by Mary Coan
• Mary did a good job in her presentation, she gave a fair introduction of MEMs, their properties and they work. She also mentioned the drawbacks of NEMs and fabrication processes.
• Even though Mary mentioned applications of NEMs more details in state of the art could have been shown.
• Mary was very fluent, and gave a good talk, the only thing missing in my opinion was the further research needed in this topic, and a little bit more fluently when answering questions.
• I believe that MEMS/NEMS devices have longevity problems as nano-structures tend to “wear out” pretty fast. How is this being resolved?
• Another problem with MEMS devices is the stiction problem during and following the etch of sacrificial layer. How are people addressing this issue?
• How do manufacturers batch fabricate NEMS devices and maintain the same physical/electrical/thermal properties? In such small scale, the variation of properties that moving parts have could be very large.