a well prepared data and structure of slides.. you will not fined anywhere else.

1. Faculty of Electrical Engineering and Computer Science
Master of Electronics Engineering (MScEE)
MMM
MEMS
Stiction and Anti-Stiction
Referent
Khalil Ahmed Rashid
6. July 2012
333690 - Microsystems

2. Structure
1. Introduction to MEMS
2. MEMS Sensors and Actuators
3. Failure Mechanisms in MEMS
4. Stiction Effect on MEMS
5. Creteria for Stiction in Microstructures
6. Remedy or Anti-Stiction Procedures
7. Stiction effect on Graphene
8. Conclusion
9. References
Referent: Khalil Ahmed Rashid
2

3. MOTIVATION (SMART PHONE BOARD)
MEMS sensors growth: from $ 3.55B in 2009 to $ 7.91B in 2015.
Referent: Khalil Ahmed Rashid Reference: http://www.i-micronews.com/lectureArticle.asp?id=5147
3

4. Introduction to MEMS
Micro
Electro
Mechanical
Systems Size between 1 to 100 um
Miniature devices formed by
combining mechanical parts and
electronic circuits, mostly on a
semiconductor chip, with
dimensions of millionths of a meter.
Referent: Khalil Ahmed Rashid Reference: http://www.analog.com/en/press-release.
4

5. MEMS Sensors & Actuators
Sensors:
Pressure Sensors
Proximity Sensors
Image Sensors
Accelerometers
Air bag crash sensors
Active suspension systems
Antilock brake systems
Ride control systems
Referent: Khalil Ahmed Rashid
5

6. MEMS Sensors & Actuators
Used for output or processing and produce some physical
Actuators:
changes.
Microphones
Fuel injection nozzles
Inkjet print heads
Gyroscopes
Electrostatic Resonators
Thermal actuators
Magnetic actuators
Reference:http://www.flint.co.uk/news/ ,
Referent: Khalil Ahmed Rashid http://www.eeweb.com/news/ultralow-noise-mems-microphone-ic/
6

7. FAILURE MECHANISMS IN MEMS
Stiction Effect
Bonding between dissimilar materials
Thermal cycle
Shock & vibration
Humidity
 Radiation
Moving parts at resonance
Referent: Khalil Ahmed Rashid
7

8. STICTION EFFECT
The moving parts of
micromechanical
machines tend to seize up
under the forces of Unintentional
sticking and friction. Adhesion
It is the static friction
that needs to be
overcome to enable
relative motion of
stationary objects in
contact.
Reference: http://www.smartertechnology.com/c/a/Technology-For-
Referent: Khalil Ahmed Rashid Change/MIT-Harnesses-Void-to-Nix-Friction-in-MEMS-/
8

9. STICTION TWO STAGES
Release Related Stiction
It occurs during the process
of the sacrificial layer
removal in fabrication of
microstructures, and such
Stiction is caused primarily
by capillary forces.
In Use Stiction
Adhesive attractions exceed restoring forces.
Surfaces permanently adhere to each other
causing device failure.
Accures due to high Humidity and Temperature.
Reference:http://www.silvaco.com/tech_lib_TCAD/simulations
Referent: Khalil Ahmed Rashid tandard/2005/aug/a3/a3.html 9

10. STICTION CATEGORIES
Mechanical Collapse Induced by Capillary Force
Due to fabrication of
suspended elements in MEMS.
If etching is performed in a
liquid environment, a liquid
bridge will be formed between
the suspended member and the
substrate, when the liquid is
removed during a dehydration
cycle, yielding an attractive
capillary force which may be
sufficiently strong to make it
collapse.
Referent: Khalil Ahmed Rashid
10

11. STICTION CATEGORIES
Contact Stiction and Peel Number
Stiction due to movable MEMS microstructures to the
substrate.
Peel number: proposed by Mastrangelo and Hsu
It is the ratio of elastic strain energy stored in the deformed
strip to the adhesion between the strip and the substrate.
If Np > 1, will not stick to substrate
If Np < 1, will stick to substrate
Referent: Khalil Ahmed Rashid
11

12. STICTION CATEGORIES
When the gap between contilever and sustrate is few
Stiction by van der Waals and Casimir Forces
micrometers then there is an adhesion force called Casimir
Forces. Casimir force has been associated with van der
Waals forces.
Van der Waals: a < lamda A = sepration
Lamda= retardation length
Casimir Force : a >~ lamda between ground to excited state
Referent: Khalil Ahmed Rashid Reference: http://www.azom.com/article.aspx?ArticleID=5542
12

13. ANTI-STICTION IN MEMS
Reducing Release Related Stiction
Texturing the surfaces to reduce
the contact area like periodic
array of small supporting post,
commonly known as "dimples"
can be introduced.
By effectively reversing the shape of
the water meniscus which forms
underneath microstructures during
the drying process.
This effect can be quantified by
measuring the water contact angle
on these surfaces.
Referent: Khalil Ahmed Rashid Reference:
http://www.lbl.gov/ritchie/Programs/MEMS/Wear.html 13

14. ANTI-STICTION IN MEMS
Reducing In Use Stiction
1. Using surface roughening and surface coating with
low surface-energy materials.
2. By reducing friction between microstructures.
 Self-assembly mono-layers(SAMs) coatings.
 Diamond-like carbon (DLC) coatings.
Reference:
http://fgamedia.org/faculty/rdcormia/NANO/nanostructures/sams.htm
http://www.directindustry.com/prod/jenoptik-i-optical-systems/diamond-like-
Referent: Khalil Ahmed Rashid carbon-coatings-14476-871121.html 14

15. ANTI-STICTION IN MEMS
Reducing In Use Stiction (conti…)
3. Eliminate the need for large input signals (or
mechanical probing) in the start-up phase in micro-
engines.
4. Better packaging for environments (thermally stable
to 400~ in various, including oxygen containing)
Referent: Khalil Ahmed Rashid
15

16. ANTI-STICTION IN MEMS
Graphene and NANO-Technology (Future of MEMS)
The lubrication effect is depends on the number of
layers of graphene in the graphite.
More layers means better lubrication.
Reference:
Referent: Khalil Ahmed Rashid http://spectrum.ieee.org/semiconductors/materials/research-
promises-better-lube-for-nano-machines 16

17. Referent: Khalil Ahmed Rashid
17

18. CONCLUDING REMARKS
The extremely high surface-to-volume ratio of MEMS
makes interfacial Stiction, friction and wear
significant factors in determining device reliability.
MEMS proved to be a break through technology
because of many possible applications in almost
every field.
These important problems must be solved in best
way for production of reliable and long lasting MEMS.
Referent: Khalil Ahmed Rashid
18

19. References
1. Maboudian R, Ashurst WR, Carraro C. Tribological challenges in micromechanicM
systems. Tribol Lett, 2002, 12(2): 95~100
2. Ashurst WR, Yau C, Carraro C, et al. Alkene based monolayer films as anti-stiction
coatings for polysilicon MEMS. Sensors Actuators, 2001, A91(3): 239~248
3. Ashurst WR, Yau C, Carraro C, et al. Dichlorodimethylsilane as an anti-stiction
monolayer for MEMS: A comparison to the octadecyltrichlosilane self-assembled
monolayer. J Microelectromech Syst, 2001, 10(1): 41~49
4. Li QY, Yu SW. A model of computation of elastic and plastic contact considering
adhesion effect. Int Y Nonlinear Sci Numerical Simulation, 2002, 3(3-4): 599~602 Zhao
YP.
5. Morphological stability of epitaxial thin elastic films by van der Waals force. Arch Appl
Mech, 2002, 72(1): 77~84
6. Zhao YP, Li WJ. Surface stability of epitaxial elastic films by the Casimir force. Chin Phys
Lett, 2002, 19(8): 1161~1163
7. Serry FM, Walliser D, Maclay GJ. The role of the casimir effect in the static deflection
and stiction of membrane strips in micromechanical systems (MEMS). J Appl Phys,
1998, 84(5): 2501~2506
8. Johnstone RW, Parameswaran M. Theoretical limits on the freestanding length
cantilevers produced by surface micromachining technology. J Micromech Microeng,
2002, 12(6): 855~861
19

20. Q&A
Thanks for your attention !
Khalil Ahmed Rashid 20