G3_NEMS

NANOELECTROMECHANICAL SYSTEMS (NEMS)

Mary Coan

April 6th 2010

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

http://www.nanowerk.com/spotlight/spotid=2431.php

http://nano.caltech.edu/gallery/group2.html

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

http://www.svtii.com/files/MEMS-NEMS-SVTI.pdf


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

http://www.svtii.com/files/MEMS-NEMS-SVTI.pdf


http://www.kschwabresearch.com/articles/detail/11

Outline



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


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


http://palasantzas.fmns.rug.nl/NEMS.html

http://phycomp.technion.ac.il/~phr76ja/boston/what2.html

Outline



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


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


http://www.gizmag.com/nanoscale-light-resonator/13401/picture/105479/

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.

http://www.semiconductor.net/article/444199-Scientists_to_Conquer_Casimir_Effect_Enable_NEMS.php

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

http://www.texmems.org/

http://www.nems.se/nimble.html

Outline



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

http://books.google.com/books?q=+bibliogroup:%22Nano-+and+microscience,+engineering,+technology,+and+medicine+series%22&source=gbs_metadata_r&cad=9



http://books.google.com/books?q=+inauthor:%22Sergey+Edward+Lyshevski%22&source=gbs_metadata_r&cad=9

http://books.google.com/books?q=+inauthor:%22Sergey+Edward+Lyshevski%22&source=gbs_metadata_r&cad=9

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



Bulk Micromachining along crystallographic planes

Animated Version


(100) Silicon Wafer P+ Si

Photo Resist

SiNx

UV Light



Left image: http://www.memx.com/ Right Image: http://www.npl.co.uk/science-+-technology/nanoscience/surface-+-nanoanalysis/mems-particle-detector

http://www.memx.com/

http://www.npl.co.uk/science-+-technology/nanoscience/surface-+-nanoanalysis/mems-particle-detector

Outline



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


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


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


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


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




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


Ultrahighfrequency oscillators provide a comparatively simple means for implementing a wide variety of practical sensing applications

Opportunities for nanomechanical frequency control, timing and synchronization


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


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



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


Integration of the freely suspended HCG mirror with a variety of nanomechanical actuators that can be designed for different values of mechanical stiffness



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)


Outline



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

Questions

G3Rebuttal: Nanoelectromechanical Systems

NMEs

Mary Coan

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.

G1

Review : Nanoelectromechanical Systems (NMEs)

Edson P. Bellido Sosa

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

Alfredo Bobadilla

G2


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

G4


Diego A. Gómez-Gualdron

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

G5


Norma Rangel

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.

Jung Hwan Woo

G6


• 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.

G3_NEMS

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