Design and Fabrication of a Multifunctional Scanning Probe

2008 ASPE Annual Meeting

1. 23rd ASPE Annual Meeting
October 19-24, 2008, Portland, Oregon
DESIGN AND FABRICATION OF A
MULTIFUNCTIONAL SCANNING PROBE WITH
INTEGRATED TIP CHANGER FOR FULLY
AUTOMATED NANOFABRICATION
Curtis R. Taylor
1
and Kam K. Leang
2
1
Department of Mechanical and Aerospace Engineering
University of Florida, Gainesville, FL
2
Department of Mechanical Engineering
University of Nevada-Reno, Reno, NV

2. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 2
Outline
• -
NeedforProbe basedNanoscaleTools
•Challenges for nanoscale fabrication
•Advantages of probe-based tools
•Limitations and challenges of probe-based tools
•
AutomatedTipChangingSystemConcept
•MEMS Thermally-Actuated Gripper and Integrated Proximity Sensor
•Advantages/Benefits/Novelty
•Key Applications Enabled by System
•
, ,
Design Modeling andFabricationResults
•Cantilever Design
•Dynamic Modeling
•Coupled Electro-Thermo-Mechanical Modeling
•Fabrication Process
•Fabrication of Prototype

3. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 3
Nanoscale Fabrication Tools
Expensive Tools
require large fabs/cleanrooms
Complex
Processes
FIB
MicroFab
•
TOPDOWN
Fab Tools
Non-Planar Surface Features
–Mesas, Trench, Line and Hole
geometries via:
–E-beam lithography
–FIB sculpting
–Micromachining/fabrication
•
BOTTOMUP
Fab Processes
Strain and Chemical Surface Modification
–Heteroepitaxial Strain
–Ion Implantation
–Self-Assembly
Self-Assembly

4. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 4
Advantages of Fabrication Via Probe Tip Tools
Arrays of 1,000s of
probes can be used to:
manipulate, pattern, machine, scribe,
write, deposit, and
engineer material surfaces
at the nanoscale with:
<1 nm resolution
on diverse materials
without costly cleanroom
processes
55,000 replicas (88 million nanofeatures)
over 1 cm
2
in less than 30 minutes
Mirkin et. al.,
Angew. Chem. ,
2006 (45), 7720
T. Kenny, 2007
IBM’s Probe-based Memory
Technology >1 Tb/in
2

5. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 5
Limitations and Challenges for Probe
Tip NanoManufacturing
•Tip Wear
•Cross-contamination
3.Throughput
•single tip
•> 5 minutes to change tip
debris
fouled tip
•50+ different probe tips and microscopy modes - /
nointegratedplatform manualtip

changeproducesslowthroughput
nanomachinin
g tip
nanolithography
tip
new tip worn tip
1.
1.
2.
3.
10 um
r ~ 10 nm

6. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 6
Probe Tip Changer For Fully
Automated Nanofabrication
To address the critical issues of throughput, tip wear,
repeatability, scalability, and limited functionality of
probe-based nanofabrication
• Enhance throughput
• Expand functionality
• Enable fully automated nanofabrication
• Provide method for scalability and robust
fabrication
APPLICATIONS:
• Nanoscale Rapid Prototyping
• Desktop Nanofactory
• Hybrid Printing of Nanostructures
Funded by NSF CMMI Grant #0726778

7. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 7
Tip Changing System Concept

8. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 8
Cantilever Design
Specifications
•
DesignSpecsand
Requirements
–compatible with existing
AFMs
–actuation
–stiffness
–resonant frequency
–gripping force and tip
stability
• -
ThermallyActuated
Gripper
–High current density in smaller
arm results in higher heating
and thermal expansion.

9. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 9
Thermally-Actuated
Cantilever Design Concepts
Single FlexureMultiple FlexureV-Flexure
flexures
V-flexure
High current density in smaller arm results in higher heating and thermal expansion

10. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 10
Static/Dynamic Modeling

11. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 11
Analytical Model of Cantilever Thermal-Actuation
Huang et. al., J. Micromech. Microeng., 9 (1999) 64-70
-kA
dT
dx
é
ë
ê
ù
û
ú
x
+J
2
rADx=-k
p
A
dT
dx
é
ë
ê
ù
û
ú
x+Dx
+SDxw
T-T
s
R
T
joule heating conductive heat transfer
DL=aLT-T
ref( )
d
deflection

12. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 12
FEA Electro-Thermal-Mechanical Model
T
d
Q
electric potential distribution,
current density
conduction,
convection heat
transfer, temperature
joule heating temperature
deflection
thermal strain, Hooke’s
law, deflection
Governing
Equation
Constants
B.C.s

r
J=s
r
E
r
Jg
r
E = Q

-ÑgkÑT()=Q+
h
dA
T
ext-T( )

s=De
-Ñgs=F
V,r(T)
V(0)=0
V(L)=V
0
k,h
T(0)=T(L)=298K
heat flux on other boundaries
a,E
d(0)=d(L)=0
COMSOL
Multiphysics

13. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 13
Comparison of FEA and Analytical Model
Results of ‘multiphysics’ FEA model in agreement with analytical model
*Note: FEA model includes convective contribution
Same dimensions and parameters used in
Huang model

14. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 14
Application of FEA Model to Design of Cantilevers
T
d
Q
electric potential
distribution, current
density
conduction,
convection heat
transfer, temperature
joule heating temperature
deflection
thermal strain,
Hooke’s law,
deflection

15. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 15
FEA Modeling of Design Concepts
single
flex
multiple
flex
V-flex fails by contact of hot arms
1200 K = thermal
failure
max ~
2V
max ~ 3
um

16. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 16
Fabrication of Prototype
•3 mask, SOI process

17. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 17
Prototype Fabrication
•Rapid Prototyping of Cantilever
concept has been performed
•Prototype of Silicon probe fabricated

FutureWork
•Testing
•Optimization
•Modular Tip Design and Fab

18. 23rd ASPE Annual Meeting, Oct. 19-24, 2008 Slide 18
Summary
•
-
NeedforProbe basedNanoscaleTools
•Sub 1 nm resolution
•Low cost versus energetic beam tools and bottom up processes
•
AutomatedTipChangingSystemConcept
•Addresses key issues of tip wear, cross-contamination, and throughput
•MEMS Thermally-Actuated Gripper and Integrated Proximity Sensor
•Key Applications Enabled by System
•Nanoscale Rapid Prototyping
•Nanofactory
• , ,
Design Modeling andFabricationResults
•Prototype cantilever designed
•Coupled Electro-Thermo-Mechanical model developed and validated
•Fabrication of prototype