nanoscale materials and device characterization program darpa grant # hr0011-05-0046 year 1 research...
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DARPA
Nanoscale Materials and Device Characterization Program
DARPA Grant # HR0011-05-0046
Year 1 Research Review San José State UniversityAugust 29, 2006
2
DARPA
Scope
Improve SJSU capabilities/expertise in Materials Characterization
Advance research in the area of nanotechnology for electronics, data storage and biosensor applications
Collaborative projects between SJSU, NASA Ames Center for Nanotechnology and IBM Almaden Research Center
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DARPA
Personnel
15 students 10 graduate research assistants, 5 tech
support 9 faculty
ChE, MatE, ME, EE, Biol, Phys, Chem 4 technical staff (part-time) 8 industry collaborators
NASA and IBM
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DARPA
Research Facilities
SJSU Materials Characterization and Metrology Center ([MC]2) SEM (CME), TEM (Biol), Solid State Lab (Phys)
SJSU Microelectronics Process Engineering Laboratory (MPEL)
SJSU Microelectromechanical Systems Laboratory NASA Center for Nanotechnology IBM Almaden Research Center Stanford Nanofabrication Facility (SNF) Stanford Materials Characterization facilities Stanford Synchrotron Research Laboratory
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DARPA
Student Presentations
SJSU site NASA site IBM site
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DARPA
SJSU Site Projects
Synthesis and Characterization of Magnetic Nanoparticles
DARPA
Synthesis, Structural, and Magnetic Characterization of Monodisperse Unary Cobalt and Binary Iron-Platinum Magnetic Nano-particles
Mr. Abhishek Singh, Dr. Gregory L. Young, Dr. Kiumars Parvin, Dr. David Bruck
San José State University
August 29, 2006
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DARPA
Outline
Significance and Applications Project Tasks Summary of Work Acknowledgements
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DARPA
Significance and Applications
Significance Size, morphology, and magnetic properties
Applications Medical: MRI Imaging, Drug Delivery Electronic: Data Storage (Disk/Flash) MEMS: Magnetic Switches
Project Scope Synthesis and characterization of size and magnetic
properties of cobalt and iron-platinum nano-particles
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DARPA
Project Tasks
Synthesis of Cobalt Nano-particles Isolate nanoparticles with a diameter of < 50 nm by
fractionation Characterized by XRD, TEM
Size Control By Varying Surfactant Control the size distribution of the nano-particle size Characterized by XRD, TEM
Magnetic Characterization Magnetic properties of cobalt nano-particles quantified as
a function of size distribution (t-Butyl vs. t-Octyl) Characterized by VSM
Synthesis of FePt Nano-particles Binary nano-particles of FePt < 40nm in size
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DARPA
Synthesis of Cobalt Nano-particles
Thermal Oxidation/Reduction of CoCl2 2Cl- 2Cl + 2e-
Co2+ + 2e- Co Synthesis conducted within inert atmosphere
80 mL Octyl Ether
1.3 mL Oleic Acid
Heat to 100 C
Surfactant
Heat to 200 C
4 mL Super-Hydride ®0.52 g CoCl2
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Synthesis of Cobalt Nano-particles.
TEM results from trioctylphosphine based synthesis Approximate particle size is 8 nm
Bar = 50 nm
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XRD Results: Alza Corp. and UC Berkeley
Position [°2Theta]40 45 50 55
Counts
0
200
400
010000200003000040000
Co Nanocrystal
Cobalt Standard
42 44 46 48 50 52 54 56 582Theta (°)
0
20000
40000
60000
80000
Intensity (cps)
Analysed using powder diffraction method.
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DARPA
XRD Results: Rigaku Corp.
20
30
40
50
60
70
Inte
nsity(C
PS
)
97-005-8889> CoO - Cobalt Oxide
97-003-9098> Co - Cobalt - Alpha
97-003-4684> Co - Cobalt - Beta - Ht
97-001-7588> Heterogenite - CoO(OH)
97-003-2459> Co - Cobalt - Delta
30 40 50 60 70
Two-Theta (deg)
t-Octyl Co sample performed using parallel-beam analysis.
Results show presence of CoO, fcc-Co, hcp-Co Potential sample preparation issues
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Surfactant Size Control Study
Literature suggests that utilizing different surfactants can control nano-particle size. A bulkier surfactant provides greater steric hindrance to yield
smaller nano-particles. Tributylphosphine vs. Trioctylphosphine utilized for study.
t-Butyl Sample, Bar = 50 nm t-Octyl Sample, Bar = 50 nm
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DARPA
Surfactant Size Control Study
Siz
e (
nm
)
tB Size (nm)tO Size (nm)
22.5
20.0
17.5
15.0
12.5
10.0
7.5
5.0
Boxplot of t-Octyl and t-Butyl Synthesized Cobalt Nano-particles.
Size (nm)Fr
eq
ue
ncy
2118151296
16
14
12
10
8
6
4
2
0
8.382 1.718 6314.72 2.017 63
Mean StDev N
tO Size (nm)tB Size (nm)
Variable
Normal Histogram of t-Octyl and t-Butyl Synthesized Cobalt Nano-particles.
• Avg. t-Octyl Size = 8.4 nm, Std. Dev. = 1.4 nm.
• Avg. t-Butyl Size = 14.7 nm, Std. Dev. = 2.0 nm.
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DARPA
Magnetic Moment vs. Temperature
Moment vs. Temperature at Constant Field
1.1
1.15
1.2
1.25
1.3
1.35
0 50 100 150 200 250
Temperature (K)
Mo
me
nt
(em
u)
t-Octyl Co sample analyzed at 2000 Oe applied field 100 temperatures analyzed from 6.5 to 210 K Sample preparation still requires refinement
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Magnetic Moment vs. Field at Varying Temperature
Moment vs. Field at T = 5K
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-15000 -10000 -5000 0 5000 10000 15000
Field (Oe)
Mo
men
t (em
u)
Moment vs. Field at T = 40K
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-15000 -10000 -5000 0 5000 10000 15000
Field (Oe)
Mo
men
t (em
u)
Moment vs. Field at T = 120K
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-15000 -10000 -5000 0 5000 10000 15000
Field (Oe)
Mo
men
t (em
u)
Moment vs. Field at T = 270K
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-15000 -10000 -5000 0 5000 10000 15000
Field (Oe)
Mo
men
t (em
u)
Field varied from -10,000 to +10,000 Oe. 80 points of data for each analysis.
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DARPA
Synthesis of FePt Nano-particles.
Synthesis Method Thermal oxidation/reduction of FeCl2 and Pt(acac)2.
Current Work In Progress FePt synthesis requires a Schlenk Line inert atmosphere
setup due to high temperature refluxing. Synthesis chamber used for cobalt synthesis cannot easily
meet setup requirements for refluxing.
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DARPA
Summary of Work
Task 1: Synthesis of Cobalt Nano-particles Reproducible synthesis method successfully developed. Developed sample preparation techniques for XRD and
TEM analysis. Task 2: Size Control By Varying Surfactant
Successfully demonstrated that larger surfactant yields smaller nano-particles.
~8nm for t-Octyl and ~15nm for t-Butyl cobalt samples. Task 3: Magnetic Characterization
Successfully conducted VSM analysis of t-Octyl based cobalt sample. Collected M vs. T and M vs. H data.
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DARPA
Work to be Completed by December 2006
Continually improve sample preparation techniques for XRD, TEM, and VSM Reproducibility is key.
Magnetic Characterization Perform further analysis on t-Octyl samples. Perform analysis on t-Butyl samples.
FePt Synthesis Complete synthesis setup and conduct successful
synthesis runs.
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DARPA
Future Work
Setup and synthesis refinement for FePt nano-particles.
Characterization of FePt nano-particles XRD, TEM, and Magnetic
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DARPA
Acknowledgements
DARPA Grant #: HR0011-05-0046 NSF Grant #: DMR-0514068 Mr. Mehdi Varasteh, Alza Corporation Mr. Spencer Wong Ms. Maninder Kaur Mr. Neil Peters Rigaku Corporation University of California, Berkeley
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DARPA
NASA Ames Site Projects
Synthesis and Characterization of Oxide Nanowires
Electrical Characterization of Nanowires by Dielectrophoresis
Surface Area Characterization of Carbon Nanotubes for Chemical Sensor
DARPA
Synthesis and Characterization of Nanowires by a Template-Directed Sol-Gel Method
Rebka Endale, Dr. Melanie McNeil, and Dr. Geetha Dolakia
NASA Ames Center for Nanotechnology and San José State University
August 29, 2006
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DARPA
Project Purpose
Fabricate nanowires using template-directed sol-gel method
Characterize nanowires using Scanning Electron Microscope (SEM) Energy Dispersive X-ray Spectrum(EDAX) X-Ray Diffraction (XRD)
Significance- Use in nanoelectronics
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DARPA
Introduction
Nanowires are materials that have diameter in a nanometer (10-9 m) scale
Because of there sizes nanowires have unique properties than the bulk materials
Oxide nanowires Insulator Semiconductor Superconductor
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Types of Nanowire Growth
Vapor Liquid Solid (VLS) Laser Ablation Sol-gel
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Challenge
To integrate nanowires into a device, it is important to find a method of synthesizing nanowires that are High in density Uniform in size Vertically Aligned Single crystalline
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DARPA
Template-Directed Synthesis
Anodic Alumina Template (AAT)
Figure 2. SEM Image of
Anodic Alumina Template. Figure 1. Two-Step Anodization Process.
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DARPA
Sol-Gel Method
Method of deposition the desired material into the nanoporous template
Used for synthesis of oxide, nitride, and sulfide nanowires
The basic steps of fabrication of materials using the sol-gel process include Preparation of homogeneous solution by dissolving in
organic precursors in water or metal organic precursors in organic solvent
Immersing the template into the sol Annealing the template to obtain solid nanowires
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DARPA
Objectives
Fabrication of AAT with uniform Diameter Length Density
Fabrication of metal oxide nanowires Study the effects of precursor concentration,
immersion time, and annealing temperature on size and crystalline structure of nanowires
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DARPA
Results
Fabricated AAT Fabricated oxide nanowires
TiO2
ZrO2
ZnO Characterized the template and the
nanowires using SEM and EDAX
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DARPA
Anodic Alumina Templates
Figure 3. SEM images of commercially available AAT from Whatman (a) AAT fabricated using anodization (b)
a. b.
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DARPA
TiO2 Nanowires
Figure 4. SEM Image of TiO2 NWs. Figure 5. EDAX Spectrum of TiO2 NWs.
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DARPA
ZrO2 Nanowires
Figure 6. SEM Image of ZrO2 NWs. Figure 7. EDAX Spectrum of ZrO2 NWs.
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DARPA
ZnO Nanowires
Figure 8. SEM Image of ZnO NWs. Figure 9. EDAX Spectrum of ZnO NWs.
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DARPA
XRD Data
0
50
100
150
Inte
nsi
ty(C
PS
)
01-084-1285> Anatase - TiO2
01-087-0920> Rutile - TiO2
97-005-7458> TiO 2 - Titanium Dioxide - R
10 20 30 40 50 60 70
Two-Theta (deg)
Figure 10. XRD spectrum of TiO2 NWs.
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DARPA
Summary
Metal oxide nanowires have been fabricated using the sol-gel method Sol concentration Annealing temperature
Structural analysis will be performed using XRD
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DARPA
Acknowledgments
DARPA Grant #HR0011-05-0046 Dr. Emily Allen, SJSU Mr. Steven Kuo, SJSU Ms. Anastasia Micheals ,SJSU
Materials Characterization Center NASA Ames Research Center Stanford Materials Characterization
Lab
DARPA
Electrical Characterization of Nanowires
Steven KuoDr. Geetha R. DholakiaDr. Emily Allen
San Jose State University
NASA AMES Center for Nanotechnology
August 29th, 2006
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DARPA
Outline
Introduction Research Tasks Theory of Dielectrophoresis Results Summary of Work Work to be Completed
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DARPA
Why Nanotechnology?
Limit in today’s electronic device processing Physical and technical
Need an alternate method to continue shrinking devices Nanowire based transistors
Nanowires are a key group of nanoscale materials in developing these devices
Nanoelectronics benefit from knowledge of material characteristics
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DARPA
Why do we need to characterize nanowires?
Bulk properties differ from nanoscale properties Surface and grain boundary scattering Band gap changes with reduction in size
Need a method of electrical characterization of nanoscale materials in order to produce useful devices
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DARPA
Electrical properties need to be studied…but how?
Current method of electrical characterization
Wire diameter is microns wide
What happens when…
Wire diameter is only nanometers wide?
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DARPA
Research Tasks Task 1: Separation and alignment of nanowires
Removal of nanowires from templates Quick and easy manipulation of nanowires onto contact pads of
devices Task 2: Setup IV Measurement System
MMR Technologies Cryocooler LabVIEW Instrument interface
Task 3: IV Measurements Determine electrical characteristics of nanowires by a 4 probe
method Resistivity measurements across temperature range of
80K – 400K Determine band gap information for semiconducting nanowires
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DARPA
How do we manipulate nanowires when they are so small?
Dielectrophoresis Force which acts on any polarizable object in a
nonuniform electric field
Electrodes
NanowireElectric field
)()( 2rmsmDEP EKF
i
m
mprodK
Re)( where
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DARPA
3μm
E-Field Modeling
Simulation of the expected e-field was calculated using Maxwell software
E-Field expected to be strongest at corners between the electrodes
Implies that the nanowire will align toward the corners of the electrodes
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DARPA
E-Field Alignment Device Design and Fabrication
Interdigitated electrodes fabricated at Microelectronics Process Engineering Lab at SJSU
Electrodes have 3-6 um spacings
200nm Al on 700nm SiO2 insulating layer
4 in. wafer with approx. 33 devices
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DARPA
Finished Electrode Devices
SEM images of fabricated devices
Optical images of finished wafer and single device
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DARPA
Nanowire Removal from Template
AAT removed with NaOH
Nanowires released by sonication
BIG Problem!!
Anodized Alumina Template
TiO2 Nanowires
52
DARPA
E-Field Alignment of Nanowires on Devices TiO2 nanowires are
aligned across 3 – 6 um spaced electrodes by an AC bias 25Hz – 30MHz 10 Vpp
53
DARPA
Temperature Dependent Resistivity Measurements
MMR Technologies Cryocooler 80K – 400K temperature range Verified to 80K
Keithley Electrometer and Current Source LabVIEW interface to control electrometer and current source
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DARPA
Ongoing Work
Redesign of the test device for accommodation in the MMR cryocooler Au electrodes Allows for more
controlled alignment of single nanowire Possible new electrode design
(not to scale)
---- line indicates Pt lines to be written in later using FIB
4 probe measurement
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DARPA
Summary of Work to Date
Nanowire alignment on electrodes has been achieved (Task 1)
Temperature dependent resistivity measurement system completed (Task 2)
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DARPA
Work to be Completed by Dec 06
Task 3: IV Measurements on single nanowire New mask design to fabricate alignment
and measurement device Fabricate new devices Perform measurements
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DARPA
Acknowledgements
DARPA Grant #HR0011-05-0046 Rebka Endale, Dr. David Parent
San Jose State University Dr. Ann Marshall,
Stanford Nanocharacterization Lab Roger Lo, Roy Martin
Microelectronics Process Engineering Lab Gary Palmer,
NASA AMES Research Center
DARPA
Metal Impregnated Single-Wall Nanotubes for Toxic Gas Contaminant Control
Ms. Ami Hannon, Dr. Melanie McNeil and Dr. Jing Li
NASA Ames Center for Nanotechnology and San José State University
August 29, 2006
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DARPA
Purpose of Research
Development and characterization of an efficient method using single wall carbon nanotubes (SWNTs) for the control and elimination of gaseous toxins.
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DARPA
Advantages of the Carbon Nanotube Based Toxic Gas Control System
Higher absorptive capacity due to very high surface area
Low temperature conversion due to nanoscale
High surface to volume ratio Ability to direct the selective
uptake of gaseous species based on their controlled pore size
Effectiveness of nanotubes as catalyst support
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DARPA
Conversion Principle
Gas Molecules
Metal CatalystParticles (Rhodium)
1. Adsorption of gas molecules on catalyst active surface
2. Catalytic reactions SWNTs/Rh + NO N2 + O2
Or SWNTs + NO N2 + CO2
SWNTs Matrix
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DARPA
Approach
1. Surface area enlargement and measurement.
2. Catalyst impregnation of the purified SWNTs.
3. Characterization and application of SWNTs
as a catalyst / catalyst support for toxic gas
conversion.
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DARPA
Rhodium Impregnation Methods
Method 1. RhCl3 Impregnated pure SWNT1. Oxidation of SWNTs2. Mix the SWNTs-oxide and RhCl33. Dry SWNTs overnight with N2 gas 4. Reduce the Rh++ with H2
5. Wash out the remaining Cl-
6. Characterize the SWNTs-Rh
Method 2. Rh doped Pure SWNT1. Mix 1% Rh on alumina with equal amount pure SWNT2. Stir the mixture overnight3. Dry the mixture with N2 gas
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DARPATEM Image of RhCl3 Impregnated SWNTs
Figure 1. TEM image of RhCl3 impregnated SWNTs (1% Rh) (Method 1).
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DARPA
SEM Images of 1% Rh doped SWNTs
SWNT bundles
Rh-flake
Figure 2. SEM images of 1% Rh doped on SWNTs (Method 2).
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DARPA
TGA of SWNTs with Metals
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 1000 1200Temperature (oC)
We
igh
t %
K(20%)-CNTCNTRh(15%)-CNTRh(20%)-CNT
Figure 3. TGA results for different metal impregnated SWNT.
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DARPA
Micromeritics Surface Analyzer
Figure 4. ASAP 2010 physisorption unit (left side) and ASAP 2010 chemisorption unit (right side).
• Physisorption unit measures surface area, pore diameter and porosity based on physical adsorption.• Chemisorption unit measure chemical adsorption characteristics for conversion of the gas.
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DARPA
RGA Connected to ASAP
Figure 5. RGA connected to chemisorption unit to measure gases resulting from toxic gas
conversion.
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Isotherm Plot
Isotherm Plot
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 0.5 1 1.5
Relative Pressure (P/P0)
Vo
lum
e A
ds
orb
ed
, C
m3
/g
Pure SWNT
Raw Hipco
pure SWNT + Water
Rhcl3 impregnatedactivated carbon
RhCl3 impregnatedSWNT(1% Rh)Method-1Activated Carbon
Rh 1% onAlumina+SWNT(Method-2)
Figure 6. Physisorption unit results.
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DARPA
BET Surface Area
Sample BET Surface Area, m2/g
Raw SWNT 536.419
Activated Carbon 1120.542
Pure SWNT 1463.525
RhCl3 Impregnated Activated Carbon 851.853
Rh 1% on alumina+SWNT 579.676
Pure SWNT+ Water 863.590
RhCl3 impregnated SWNTs 825.7837
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DARPA
Future Work and Tasks
1. To make different catalyst metal impregnated SWNTs. 2. Analyze effectiveness of different
catalysts for NO conversion: Rh, Pd, Pt 3. Optimize the NO gas decomposition conditions. 4. To study chemisorption with gases
other than NO on SWNTs.
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DARPA
Acknowledgements
DARPA grant #HR0011-05-0046 NASA Ames Research Center Dr. Emily Allen
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DARPA
IBM Almaden Site Projects
Fabrication and characterization of solid-state nonvolatile memory devices in polymeric semiconductor composites
Nanoporous thin film characterization using transmission small angle x-ray scattering and x-ray reflectivity
Using Nanoporous Substrates to Increase SPR Sensitivity
DARPA
Development of Imprint Lithography Method for Self-
Assembled Monolayer of Gold
Ms. Rupa Shitole, Dr. Emily Allen and Dr. Campbell Scott
IBM Almaden Research Center (ARC) and San José State University
August 29, 2006
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DARPA
Outline
Storage Class Memory Fabricating Mold/Stamp Patterning Hydrophobic and Hydrophilic
Regions Testing and Results Summary
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DARPA
Storage Class Memory (SCM)
Memory and Storage components in modern computers
Memory – SRAM, DRAM Storage – HDD Flash Memory
Reference: J.C. Scott, Science 304, pp. 62-63 (2004).
SCM
Simple design Low cost Storage medium Gold nanoparticles embedded in a
polymer Requires Self-Assembled
Monolayers (SAMs)
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DARPA
Crosspoint Device Testing
Keithley Source-Measurement Unit
Study Current-Voltage Behavior Switching
Characteristics Bistability
Reference: L.D. Bozano et al., Applied Physics Letters 84, pp. 607-609 (2004).
Desired IV Curve
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DARPA
Research Tasks
Fabricating the stamp/mold for developing the crosspoint architecture.
Patterning hydrophobic and hydrophilic areas on which SAMs can be made.
Obtain gold monolayer by self assembly on the polymer.
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DARPA
Fabricating Mold/Stamp
Resist Application Exposure Develop Reactive Ion Etch (RIE) Strip Photoresist Cast and Cure PDMS Mold Detached
PDMS
Mold
Silicon
Photo
Resist
Shine Light Mask
Stamp
80
DARPA Cast and Cure PDMS (Polydimethylsiloxane)
Prepolymer Sylgard 184 elastomer (10:1).
Degassed in vacuum chamber. Poured onto the wafer. Added a backing glass slide. Cured in the oven at 75°C overnight
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DARPA
Etched Mold & PDMS Stamp
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DARPA
Patterning Hydrophobic and Hydrophilic Regions
Bottom Electrode Polyvinylcarbazole
(PVK) Application Soft Lithography
Process Dispensing Au
Colloidal Solution SAM Formation
Quartz
Hydrophilic Region
Stamp
Au colloidalsolution
Au monolayer
PVK
Surfactant
Cr/Au
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DARPA
Crosspoint Architecture
PVK
Cr/AuQuartz
Al
Top Al Electrode Patterned (90°Rotation)
Single Device Structure Achieved.
Au NPs self- assemble on PVK surface
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DARPA
Surfactants Examined
Product Name Chemical Formula1)TRITON QS-44 Polyether phosphate ester
2) Polyethylene-block-poly (ethylene glycol) Mol. Wt. ~575
CH3CH2(CH2CH2)X(OCH2CH2)YOH
3) Polyethylene-block-poly (ethylene glycol) M. Wt. ~1400
CH3CH2(CH2CH2)X(OCH2CH2)YOH
4) Glycolic acid ethoxylate
lauryl ether (Mol. Wt. ~360) CH3(CH2)11-13
(OCH2CH2)nOCH2CO2H
5) Brij 97 (Mol. Wt. ~709) C18H35(OCH2CH2)nOH, n~10
6) Brij 93 (Mol. Wt. ~357) C18H35(OCH2CH2)nOH, n~2
7) Tween 20 (Mol. Wt. ~1228) Polyethylene glycol sorbitan monolaurate
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DARPA
Contact Angle Measurement
PVK Surface (Hydrophobic well)
Range: 80-95 degrees Stamped Region (Hydrophilic)
Range: 10-30 degrees Surfactant used were Brij 93 and
Tween.
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DARPA
Device Testing Results
-2 -1 0 1 2 3
1E-3
0.01
0.1
Cur
rent
Den
sity
(A/c
m^2
)
Voltage (V)
(A/cm^2) Linear Fit of A20060731003_CurrDensity
-3 -2 -1 0 1 2 3 410-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
Cur
rent
Den
sity
(A/c
m^2
)
Voltage (V)
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DARPA
Surface Characterization
Image Courtesy of Vaughn Deline (IBM Almaden Research Center).
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Auger Characterization
RS 72, Position #9
17000
22000
27000
32000
37000
0 500 1000 1500 2000
Energy (eV)
Inte
nsity
(c)
S
C
N
O
Na
Si
Au
C 50%N 6%O 5%Na 5%Si 13%S 8%Au 13%
9
SEM and Auger Spectrum from Position #9
Image Courtesy of Vaughn Deline (IBM Almaden Research Center).
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Conclusions
Gold clusters were formed that were undesirable.
Bistability and switching behavior was not as expected.
Dodecanethiol was still in excess.
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DARPA
Summary
Fabricate the mold to develop 2-D crosspoint architecture using soft lithography process.
Patterning hydrophobic and hydrophilic areas on which SAMs can be made.
Investigate the performance of the crosspoint data storage architecture.
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DARPA
Acknowledgements
DARPA grant #HR0011-05-0046 IBM Almaden Research Gary McClelland, Sally Swanson, Dolores Miller, Ho-
Cheol Kim, Andrew Kellock, Vaughn Deline, Luisa Bozano, Jane Frommer and Jeremy Hamilton
Stanford Nano-Fabrication Facility (SNF) Nancy Latta
DARPA
Characterization of Pore Structure in Ultra Low-k Dielectrics Using X-ray Porosimetry
DARPA Grant # HR0011-05-0046
Mr. Jonathan Lin, Dr. Ho-Cheol Kim, Dr. W. Richard Chung
IBM Almaden Research Center, Stanford Synchrotron Radiation Laboratory, and San José State University
August 29, 2006
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DARPA
Outline
Applications Scope of Project (Milestones) Status of Each Milestone Conclusions Future Work
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DARPA
Applications
Nanoporous films (e.g. organosilicates) can lower the dielectric constant, k, below 2.0 by the nano-pores.
The pore size must be substantially smaller than the minimum feature size, and the pore distribution should be uniform throughout a device structure.
Semiconductors, biosensors, fuel cells, food package, etc.
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DARPA
Scope of Project (Milestones)
Control morphology and pore size are critical for ultra low-k (<2.0) dielectric materials in semiconductor devices.
Milestone 1 Preparation of nanoporous organosilicate thin films Measure density, thickness, and roughness using X-ray
reflectivity Milestone 2
Thermal expansion coefficient (CTE) determination Milestone 3
Design and build X-ray porosimetry (XRP): build environment control chamber and flow control system and testing
Milestone 4 Pore characterization using the transmission Small Angle X-ray
Scattering (SAXS), data reduction and analysis
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DARPA
Material Preparation
Make solutions of both inorganic precursor and organic copolymer.
Spin coating at a speed of 2000 rpm for 30 sec (about 300 nm thin) on 3” silicon wafers.
Curing and Heating process: Crosslink the inorganic precursor (170~200ºC) Further heating: to remove the organic polymer (450ºC)
97
DARPA
X-ray Reflectivity (XR)
XR is a simple and powerful technique that measures density, thickness, and roughness of thin films.
0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30 0.32Omega-2Theta (o)
100
2
3
4
6
1000
2
3
4
6
10000In
tens
ity (
cps)
Critical angle ( qc) is as a function of film density (ρm)
Periodicity of fringes (Δq) determines the thickness (t)
2q
t
Z
A
c
qcm *
2
C: constant, A: average atomic weight, Z: average atomic number
Detector X-Ray
Source
Porous FilmPorous FilmSubstrateSubstrate
tθ
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DARPA
Coefficient of Thermal Expansion (CTE)
The CTE can be determined by measuring film thickness as a function of temperature. The CTE of a porous MSSQ (methylsilsequioxane) thin film was calculated as 79 ppm/°C.
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DARPA
Environmental Chamber and Vapor Pressure Control
*The flowchart was modified from an NIST process
100
DARPA
Photos of the XRP System
(a) (b) (c)
(d)
(f)(e)
(a) X-ray beam source, process chamber, and detector (from the right to the left), (b) Process chamber with the PEEK dome, (c) Sample stage without the dome, (d) Flow control system, (e) Flow control unit, and (f) Mass flow controllers (MFC).
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Δqc=0.0025
Organosilicate: BTESM-bis(Triethoxysilyl)methylene
The results of porosities and pore sizes obtained from SANS and XRP are very close.
400x10-6
300
200
100
0P
ore
volu
me
(arb
. uni
t)2 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
1002
Pore radius (Å)
Low k_adsorption Low k_desorption
Method Thickness, nm
Density, g/cm3
Porosity Pore Size, radius
SANS 378 1.097 32.70 % 11.7 Å
X- ray Porosimetry
425 1.137 30.26 % 22.5 Å, f rom adsorption 11.5 Å f rom desorption
)/ln(
2
0PPRT
Vr mc
rc is the critical radius of capillarity condensation, Vm is the molar volume, γ is the liquid surface tension, R is the ideal gas constant, T is the absolute temperature.
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SAXS Result of MSSQ(Methylsilsequioxane)
Scattering profile shows multiple peaks which indicates well ordered pore structure of nano- porous film.
From the peak position at q=0.065, the first form factor peak, pore diameter can be determined as 8.7nm using the relation qR=5.765 for spherical form factor.
c is a constant, n(r) is the pore size distribution function, F(qr) is the form factor (intrapore scattering), and S(qr) is the structure factor from inter pore scattering.
0
( ) ( )I q c n r F qr S qr dr
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Conclusions
Demonstrated the X-ray reflectivity measurement on density, thickness, and roughness of nanoporous thin films
Determined the CTE by measuring film thickness as a function of temperature
Successfully built an X-ray porosimetry with reduced chamber volume and determined pore size and size distribution by model fitting to the X-ray porosimetry data
Demonstrated the ordered spherical structure of nano pores per the scattering plot from SAXS
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Work to Be Done by Dec 2006
Measure porosimetries of BTESM samples with various porosities and pore structures
Use SAXS technique to characterize the BTESM samples
Compare and analyze the results generated by X-ray porosimetry and SAXS techniques
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Acknowledgements
DARPA Grant # HR0011-05-0046 Dr. Emily Allen and Dr. Melanie McNeil, San
José State University Dr. Geraud Dubois, Dr. Joy Cheng, and Dr.
Victor Y. Lee, IBM Almaden Research Center
Dr. Mike Toney, Stanford Synchrotron Radiation Laboratory
Dr. Hae-Jeong Lee, National Institute of Standards and Technology
DARPA
An Improved Design for Surface Plasmon Resonance System
Ms. Shyama Srinivas, Dr. Melanie McNeil, Dr. Robert Miller, Dr. J.P. Samuel, and Dr. William Risk
IBM, Almaden Research Center and San José State University
August 29, 2006
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Outline
Introduction/Background Significance Research Objectives Experimental Results Summary Acknowledgement
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Introduction/Background
Biosensors - to detect and characterize biomolecules
Optical biosensors Surface Plasmon Resonance (SPR) SPR uses surface sensitive optical
resonance phenomenon
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Why SPR Biosensor?
SPR – Advantages High sensitivity Real-time analysis Label-free
SPR – Challenges Noise caused by air-bubbles High precision temperature control required Effect of variable size of biomolecules
Key to success - a careful experimental technique Hence, overcome pitfalls to obtain accurate results Modified SPR setup - to overcome pitfalls
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Significance
Increased sensitivity & adsorption selectivity
Increased number of biomolecular interactions can be analyzed
Economic benefit – Increased efficiency in medical diagnostics
Expand the use and applications of the SPR biosensors in other fields as well
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SPR Phenomenon
Figure 1: Surface Plasmon Resonance (or SPR) ( Ref: http://chem.ch.huji.ac.il/~eugeniik/spr.htm )
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SPR Flow Cell System
Figure 2. Sensorgram Result with the SPR flow cell systemRef: (http://www.biotech.iastate.edu/facilities/protein/seminars/BIACore/TechnologyNotes/TechnologyBrochure.pdf
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Research Objectives
Develop an effective technique to improve sensitivity by
Designing an effective flow cell for an SPR biosensor Testing the reproducibility of gold layer SPR
measurements
Demonstrate the use of SPR biosensor with a model using random functionalized polymers
Detect controlled layer-by-layer deposition of star polymers with no surface charge on gold/ oxide surfaces by SPR
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Project Time-line
Quarter 1- Research the flow cell design
Quarter 2 - Develop Flow cell design Quarter 3 - Design verification Quarter 4 - Layer-by-layer detection
model
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Experimental Results
FLOW CELL DESIGN A hemi cylindrical prism of BK7 glass The flow cell material - Kel-F® (nonbinding to
biomolecules) Elliptical shape - no air bubbles during the flow of the
liquid Dimension (8.3 mm*2.3 mm*0.5 mm) Vacuum to hold the wafer Magnetic clamps Twin cells for differential detection Luerlock fittings BK7 Wafers coated with gold
Thermal evaporation
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Flow Cell Design
Figure 3. Shows the design of a flow cell made of KEL-F.
Hemicylindrical prismMagnetic clamp
Kel-F®
BK7 wafer
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Flow Cell Design
Figure 4. Clear view of the Flow cell design.
Kel-F®
Twin cells (elliptical shape)
vacuum
LuerlockDIMENSIONS(8.3 mm*2.3 mm*0.5 mm)
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Design Verification
Angular SPR (831.15 nm) Check leakage Check bubble formation Comparison of the theoretical and
experimental SPR measurements
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Experimental Results
30 35 40 45 50 55 60
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
Inte
nsity
Angle
experimental high resolutiontheoretical
2nm Cr & 50nm Au &RIL
Figure 6. Shows that experimental results with thermally evaporated 2nm Cr, 50 nm Au matches with theoretical results.
30 35 40 45 50 55 60
0.0
0.2
0.4
0.6
0.8
1.0
Ref
lect
ivity
Angle
Theory
Figure 5. This data is obtained from a BK7 prism coated with gold. Difference in theoretical & exptl surface plasmons is very clear. The experimental curve is not deep & is very broad. The optical & mechanical alignment should be verified in future experiments.
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Experimental Results-Flow Cell Design
No leakage. No bubbles were formed in the flow
cell system. Excellent match with the theoretical
measurements. Repeated runs produced reproducible
results.
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Experimental Results of the Model
Layer-by layer detection of materials BK-7 wafer was used with 5 nm Cr/50 nm
Au/4 nm SiO2 Functionalized star polymers were used
for this purpose PS-NH2 1mg/ml 10 mL in THF PS-COOH 1mg/ml 10 mL in THF
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Experimental Result of Layer-By-Layer Deposition
72 73 74 75 76 77 78
200
300
400
500
600
700
800
900
1000
Inte
nsity
Angle
THF PSNH2 layer1PSCOOH layer1PSNH2 layer2 PSCOOH layer2
Figure 7. Shows that there is a steady shift of surface plasmons with the addition of PS-NH2 and PS-COOH layer on the 5 nmCr/50 nmAu/4 nmSIO2 .
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Experimental Results
36 38 40 42 44 46 48
300
400
500
600
700
800
900
1000
Inte
nsity
Angle
ORIGINAL AFTER DEPOSITION
Figure 8. Shows that there is a shift in the plasmon before and after the removal of polymers.
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Experimental Results of Layer-By-Layer Detection
• There was a steady shift in the surface plasmon with the addition of random functionalized polymer layer.
• The acid-base interaction facilitated binding on the surface.
• Experimental results demonstrated good sensitivity of the SPR biosensor.
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Summary
Designed, built and verified the flow cell design.
Developed layer-by-layer SPR detection model.
Work in progress: Installation of the peristaltic pump to
control flow rate in SPR experiments . Kinetics study using the SPR system.
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Acknowledgements
DARPA grant #HR0011-05-0046
IBM - Dr. Ho-cheol Kim, Dr. Michael Jefferson
SJSU - Dr. Emily Allen, Dr. Richard Chung, and Dr. Roger Terrill
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Overall Progress
Each Task will be completed by December
Research will continue as new Tasks as part of DMEA program
Final expenditures will include equipment not originally in budget
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Impact on state of the art
Publications expected to be forthcoming from some of the projects
New results for: SPR sensitivity, nanowire characterization, magnetic nanoparticle synthesis, nanoporous film characterization
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Impact on SJSU
Exceptional Masters student training opportunity
Growth of expertise and capabilities in materials characterization and nanotechnology
New collaborations internally and externally