Electron Beam Lithography Fabricated

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Electron Beam Lithography Fabricated Carbon
Nanofiber Sensor for Water Based
Biohazards Devin K.
Brown Nanotechnology Research Center September
22, 2009
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Clean Water is a Global Problem
According to the World Health Organization 1.1
billion people lack access to safe water 2.6
billion people lack access to proper
sanitation The greatest source of these problems
waterborne bacteria viruses parasites ...comi
ng from raw sewage, infected feces and industrial
biowaste that are not adequately sanitized before
entering the water supply.
Water, sanitation and hygiene links to health -
Fact and Figures, World Health Organization,
November 2004 
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Many Children at Risk
Diarrheal diseases from drinking contaminated
water kill 1.8 million people each year mostly
children under 5 in developing countries diarrhea
l diseases mainly due to Vibrio cholerae
bacteria causes Cholera, a rapidly fatal
illness can kill people in as little as three
hours if treatment is not provided. In 2009 a
cholera outbreak in Zimbabwe killed 4,037 and
infected over 91,000 Another bacterium,
Salmonella typhi causes typhoid fever affects
21 million people every year and kills 200,000
Cholera Epidemic in Zimbabawe Easing - WHO,
Reuters UK, March 23, 2009Typhoid Fever,
Centers for Disease Control and Prevention,
October 24, 2005
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Food Chain Also at Risk
When infected water is used to irrigate
crops feed animals or is dumped near fish and
shellfish pathogens can contaminate the food
chain Intestinal helminth infections
(worms) parasites such as Ascaris lumbricoides
(roundworm) cognitive impairment massive
dysentery anaemia affects 133 million people
with 9,400 deaths every year
Water, sanitation and hygiene links to health -
Fact and Figures, World Health Organization,
November 2004 
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Do We Really Need to Worry?
industrialized countries have a much lower
risk due to one principal reason drinking water
is usually treated with chlorine or other
disinfectants kill bacteria such as Vibrio
cholerae (cholera) Salmonella typhi (typhoid
fever)
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Chlorine Not 100 Effective
chlorination can give a false sense of
security protozoan parasites such
as Cryptosporidia Giardia lamblia and viruses
like hepatitis A and E rotavirus Norovirus can
be present in drinking water even when water is
chlorinated.
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Cryptosporidiosis Outbreak Here in USA
Cryptosporidium caused a cryptosporidiosis
outbreak in Milwaukee in 1993 400,000 cases of
serious illness 100 deaths mostly among the
elderly immunocompromised people such as
AIDS patients 
http//en.wikipedia.org/wiki/Milwaukee_Cryptospor
idium_outbreak
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Other Outbreaks in USA
2008 Salmonella Saintpaul outbreak possibly
from imported Jalapeno peppers from
Mexico linked to 1,442 cases 286
hospitalizations 2 deaths in the US CNN also
reported on the Lou Dobbs show 30,000- 40,000
unreported illnesses 100 - 250 million in
economic losses 2009 Salmonella Typhimurium
outbreak caused by peanut butter from
Peanut Corporation of America, Blakely, GA 9
deaths 691 illnesses in the US 
Investigative Outbreak of Infections Caused by
Salmonella Saintpaul, Centers for Disease Control
and PreventionInvestigation Update Outbreak
of Salmonella Typhimurium Infections, 2008-2009,
Centers for Disease Control and Prevention
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Water Municipality Infrastructure
Pathogens can also enter the water supply after
the water is treated aging or broken
watermains new developments that have left dead
ends in the old water network only water
pressure prevents contamination
entering Pathogen sources can include storm run
offs industrial and agricultural
by-products leaking septic tanks untreated
waste from infected animals and people The EPA
estimates that the expense to repair US water
infrastructure 1 trillion over the first 20
years of the twenty-first century
Clean Safe Water for the 21st Century, The
Water Infrastructure Network, 2000
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Loss of Pressure
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Lake Lanier
February 11th 2008 (1052.37ft) 
March 4th 2007 (1067.83 ft)
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Shrinking Resources
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Shrinking Resources
July 17, 2009 U.S. District Judge Paul
Magnuson rules Atlanta has three years to obtain
Congressional approval to keep using Lake Lanier
for drinking water. In the days following the
ruling, Georgia Gov. Sonny Perdue says he will
appeal the decision but also is open to
negotiations with Florida and Alabama. 
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Early Warning Water Analyzer
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Early Warning Water Analyzer
The biosensor will replace 100-year old culture
tests      Automated inline biosensing eliminate
s the need to manually collect samples, perform
laboratory test procedures, interpret test
outcomes, and communicate test results    Faster
test results 2 to 3 hours instead of 1 to 7
days    Wider test scope 25 specific pathogens
per test rather than a single pathogen
   Pathogen viability distinguishing between
dangerous live cells and ineffective dead
cells    No major infrastructure
cost eliminating the need for a biosafety
laboratory and associated equipment.   Targeting
a 50 price per test along with an instrument
price of 35-50k.
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Carbon Nanofiber Sensor
Below is a 4 inch wafer with 30 chips.
Each chip has a 3 x 3 array of 200 micron pads
shown above.
Multi-walled carbon nanofibers are grown on each
nickel dot.
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Process flow
Koehne et.al., J. Mater. Chem., 2004, 14, 676 -
684
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Electrochemical Sensor
Earl Warning Inc.

• each target pathogen has its own electrode
• single strands of nucleic acid attached to each
  carbon nanofiber
• single strands of RNA from sample come in
  contact with fibers
• complementary strands hybridize into double
  helixes
• potential applied and guanine oxidation causes
  current flow
• signals calibrated with known values to indicate
  pathogen concentration

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Types of Carbon Nanotubes
single walled carbon nanotube (SWCNT)
multi walled carbon nanotube (MWCNT)
multi walled carbon nanofiber (MWCNF)
M. Meyyappan et. al., Plasma Sources Sci. Tech.,
12, (2003) 205-216
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Single Wall Carbon Nanotubes
M. Meyyappan et. al., Plasma Sources Sci. Tech.,
12, (2003) 205-216
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Multi Wall Carbon Nanotubes
M. Meyyappan et. al., Plasma Sources Sci. Tech.,
12, (2003) 205-216
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Multi Wall Carbon Nanofibers
M. Meyyappan et. al., Plasma Sources Sci. Tech.,
12, (2003) 205-216
Koehne et.al., J. Mater. Chem., 2004, 14, 676 -
684
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Black Magic PECVD Aixtron, Inc.
carbon nanofiber growth recipe temp
800C gases444 sccm NH3 ammonia 125 sccm C2H2
acetylene pressure 6 Torr DC plasma 800
V with 15kHz pulse
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Nanofibers Grown Here at GT
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Some Points on CNF Growth

• bottom oxide layer to prevent nickel salicide
  formation
• NH3 used to prevent excessive amorphous carbon
  deposition
• carbon nanofibers have better adhesion than CNTs
• plasma assists in vertical alignment due to
  electric field in sheath, does not increase CNF
  growth process

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E-beam Evaporation
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Carbon nanotube catalyst pattern 130nm diameter
on 1um pitch 100A Cr 300A Ni
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Problem
want this
but often get this
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Non-uniform nanodot diameters
all die measured
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Evaporator Geometry
wafer holder
50mm
25mm
100mm wafer
229mm
6
12
crucible
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Wafer Point of View
130nm
PMMA
y 235nm
silicon
x1
x2
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Wafer Point of View
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130nm
PMMA
235nm
80nm
silicon
angle (degrees) nanodot size (nm) top down shape side view shape
0 130
1 128
3 123
6 116
9 109
12 80
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Crucible Location Under Sample
6.5
1. 5
2.75
6.5
crucible not centered relative to sample holder
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Deposition Rate
?
d
?
rdep deposition rate (thickness/sec) revap
evaporation rate (mass/sec) ? solid angle over
which source emits (unit less steradians) d
source to substrate distance ? material
density ? inclination of substrate away from
direction to source
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Uniformity
Case 1 d ? x
Case 2 d gtgt x
x
x
d1
d2
d1
d2
d1 ? d2
d1 lt d2
rdep (d1) ? rdep (d2)
rdep (d1) gt rdep (d2)
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if
, then
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Increasing Sample Distance
wafer holder
50mm
100mm wafer
954mm
3
crucible
in order to limit incoming angle to 3 degrees or
less across entire wafer the sample would have to
be placed almost 1m away from crucible however
this would decrease evaporation rate by 1/16.
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Electron Beam Lithography
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Thicker Resist is Worse
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Characterize your resist (dose vs. feature size)
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Wafer Layout
9 pads
30 chips
200 x 200 array of 130 nm dots
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How Many Nanodots?
200 x 200 40,000 nanodots per pad
( 9 pads ) X ( 40,000 nanodots ) 360,000
nanodots per chip
( 30 chips ) X ( 360,000 nanodots ) 10.8
million nanodots per wafer
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Dose Equation
where D dose (µC/cm2) I current (A) t time
(sec) A exposure area (cm2)
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Job Time Estimate
area of one dot p r2 7.8E-11 cm2
A ( 10.8E6 dots ) X ( 7.8E-11 cm2 ) 8.4E-4
cm2
D 1950 uC/cm2
I 2 nA
t 14 min
but actual time 76 min
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Fracture Process
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Fracture Process
subfield scanning shown in blue main deflector
vector scan shown in red. beam is blanked on and
off for each main deflector vector scan.
1. each polygon is a subfield 2. beam is blanked
between each subfield and beam is positioned by
main deflector between subfields
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Beam Deflection
Two stage deflection
50 MHz
2 MHz
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Beam Deflection
Write time much longer than expected with
scanning deviation from max of 50 MHz ( 20 nsec
per pixel )
Accounting for 2 MHz main deflector operation
still does not account ( 500 nsec per object )
Stage movement, calibrations cannot account for
extra time either .
????
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Discuss with JEOL
6 usec PDEF prep time penalty per fracture
shape ( due to voltage time settling requirement )
shot preparation time 10 shot speed
40,000 dots / array 10.8E6 dots / wafer
148,000 objects / array 399.6E6 objects / wafer
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Recalculate
observe 14 sec to write one 40,000 array of 200 X
200 dots
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area exposure time 3.1 sec t ( D A ) / I
PDEF prep time penalty 8.9 sec 6 usec per
object shot prep time penalty 2.3 sec 10 shot
speed --------------------------------------------
-- 14.3 sec
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Problem 62 of write time is not dependent on
beam current or resist sensitivity
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Customer A
silicon nanoimprint stamp array of 200 nm
diameter holes on 300 nm pitch covering a 2.5 cm
x 2.5 cm area thats 6.9 billion holes! close to
300 billion fractured shapes!
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Can We Just Increase Current?
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Fracture Limitation
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Apply Large Beam Shape
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CAD File
200 nm squares on 300 nm pitch
2.5 cm X 2.5cm
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Condition 1
300 nm
aperture 3, 60um current 2 nA shot pitch 6
nm 10 modulation, effective dose 220 uC/cm2
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Condition 2
300 nm
aperture 3, 60um current 5 nA shot pitch 10
nm 10 modulation, effective dose 220 uC/cm2
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Condition 3
300 nm
aperture 6, 100um current 15 nA shot pitch 14
nm 10 modulation, effective dose 220 uC/cm2
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Increase Dose
300 nm
300 nm
10 modulation effective dose 220 uC/cm2
30 modulation effective dose 260 uC/cm2
aperture 6, 100um current 15 nA shot pitch 14
nm
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Increase Dose
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Customer B
bit patterned media array of 10 nm diameter
holes on 40 nm pitch covering a 3 mm x 3 mm
area thats 5.6 billion holes! 230 billion
fractured shapes!
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Can We Just Use Squares Again?
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Dots on the Fly Method
increasing shot pitch
20 nm
40 nm
6 nm
10 nm
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CAD File
CAD file 3 x 3 mm square thats it!
subscanner field limited to 4 um X 4 um therefore
large squares divided up into 4 x 4 um segments
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dots on the fly
Mag 1M X!
10 nm!
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Total Time Reduction
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Questions?
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1 Question I get asked

• Where is Joel Pikarsky?
• Answer