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2010 - |
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Jan. 7, 2010 |
No TeleSeminar -- Holiday
Schedule |
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Jan. 14 |
Host: Juan de Pablo, H. Curler
Distinguished Professor of Chemical Engineering, Director, Materials
Research Science and Engineering Center, Department of Chemical and
Biological Engineering, University of Wisconsin-Madison
Presentation by: Juan de Pablo and Gregory
Toepperwein, PhD Candidate, Department of Chemical and Biological
Engineering, University of Wisconsin-Madison
Topic title: “Supercritical carbon dioxide compatible
additives for environmentally benign photoresist development.”
Abstract: Supercritical carbon dioxide (scCO2) is a promising
solvent for photoresist development due to its environmentally benign
nature. It is nontoxic, inert material, and in the context of photoresist
development it has been shown to inherently reduce line edge roughness (LER).
However, its widespread adoption has been hindered by the poor solubility of
most traditional photoresist materials in CO2. In this work we examine the
use of scCO2 additives aimed at enhancing resist solubility. We first
examine quaternary ammoniums salts (QAS), which are highly effective but
rely on some degree of fluorination. By developing an understanding of the
mechanisms of solubility enhancement we leverage our knowledge of QAS to
develop non-fluorinated additives of equal efficacy. Lastly, we briefly
discuss the use of molecular glasses as photoresists due to their lower LER
and good compatibility with scCO2. (PPT-zipped) |
|
Jan. 28 |
Host: Reyes Sierra, Chemical and
Environmental Engineering, University of Arizona
Presentation by: Mike Frisch, Ph.D., P.E., International
SEMATECH Manufacturing Initiative
Topic title: “The Feasibility of Alternative and Renewable
Energy in the Semiconductor Industry”
Abstract: Sustainable manufacturing has become increasingly
important to the semiconductor industry recently, especially as governments
accelerate the pace towards greenhouse gas (GHG) measurement and carbon cap
and trade policies. Energy conservation and alternative and renewable
energy (AE/RE) usage are two means of enhancing sustainability and reducing
greenhouse gas emissions. Alternative energy (AE) technologies, such as
fuel cells and cogeneration, offer improved efficiencies compared to
conventional fossil fuel technologies while renewable energy (RE) can be
generated from a virtually infinite renewable resource, such as sunlight,
wind, geothermal, and wave energy. AE/RE technologies have enjoyed a surge
in both popularity and investment due to spiking energy prices and concerns
for GHG-induced climate change. More recently, promotion and development of
AE/RE technology and infrastructure has been touted as having the potential
to recreate the world economy and end the global economic downturn. This
movement has gained political force in many countries and, as a result,
there are generous financial incentives available from local, state and
federal governments to install or use AE/RE technologies. Furthermore,
large-scale deployment of AE/RE technologies has resulted in increased
efficiencies and decreased manufacturing and installation costs. Reduced
costs, combined with expanded financial incentives, may create an
environment where the price of AE/RE is competitive with conventional energy
generating technologies.
The International SEMATECH Manufacturing Initiative (ISMI) commissioned a
study of the feasibility of implementing AE/RE at semiconductor
manufacturing facilities. The study involved selecting and investigating
commercially available technologies that could be applied to member company
sites, surveying the semiconductor industry for its experience and
preferences, and determining the economic and technical feasibility of each
technology at member company locations. This work focused primarily on the
direct installation of AE/RE technologies. The purchase of renewable energy
and renewable energy certificates (RECs) is also briefly discussed. (PDF) |
|
Feb. 11 |
Host: Farhang Shadman, Chemical & Environmental Engineering,
University of Arizona
Presentation by: David Lynch, Chief Technical
Officer, Solar Technology Research Corporation, Tucson AZ, and Professor of
Mining Engineering, and Materials Science & Engineering, University of
Arizona
Topic title: "Winning the Global Race for Solar Silicon: The
Sequel"
Abstract: Last year I reported on the first month of
experimentation in STRC’s effort to produce low cost solar silicon by
refining of metallurgical-grade silicon. Since that initial report the
Company has adjusted its main focus away from boron to phosphorus to take
advantage of shortcomings experienced by competitors. The Company has
achieved 95% reduction of P in silicon (from 40 ppmw to 2 ppmw), and at the
same time reduced the B content by 70% (from 20 ppmw to 6 ppmw). Producers
of p-type photovoltaics (PVs) desire silicon with no more than 0.42 ppmw B,
and P content no higher than 0.40 ppmw. The difference in our numbers for
the two elements and what PV producers want, and the discovery of high
purity silica deposits with unusually low B content has led us to look to
integrating upstream to include reduction of the high purity silica with
high purity reducing agents using STRC’s technology. The additional cost of
the reducing agents is offset by fewer refining operations. We have
identified four different processing routes with production cost estimates
(prior to unidirectional solidification) ranging from $8.22 to $13.59 per kg
of Si. Those figures represent only 24% to 39% of the production cost of
Siemens silicon, the primary silicon used today to produce PVs. The lower
cost figures involve including kerf waste from wire sawing of silicon
ingots. While the silicon content of the waste is advantageous, it is the
SiC in the waste that we seek. (PDF) |
|
SRC/SEMATECH ERC Annual Review
Meeting - February 17-18-19, 2010 |
|
Feb. 25 |
NO TELESEMINAR |
|
March 11 |
Host: Farhang Shadman, Chemical & Environmental Engineering,
University of Arizona
Presenter: Krishna Muralidharan, Materials Science and Engineering, University of Arizona
Topic title: "Novel phononic metamaterials for
acoustic and thermal applications"
Abstract:
Phononic metamaterials (PM) such as
phononic crystals have been the subject of much study over the past few
decades because of their ability to exhibit a multitude of different
properties. Phononic crystals are the acoustic counterparts to photonic
crystals, and consist of periodic arrangements of inclusions in a physically
dissimilar matrix. The size, periodicity as well as the differences in the
impedance of the constituent materials can cause Bragg scattering, leading
to phononic band-gaps, negative refraction, and zero-angle refraction across
a broad spectrum of frequencies. These properties can be suitably exploited,
leading to applications of such systems as filters, wave-guides, collimators
and lenses.
In this talk, we will initially focus on the applications of PM as acoustic
lenses and acoustic collimators. Specifically, using a combination of
experiments and theory, we examine a 'flat-lens' phononic crystal consisting
of a triangular lattice of steel rods in a methanol matrix, and its ability
to achieve super-resolution via the coupling of evanescent waves with slab
modes; next we report on the properties of a phononic crystal consisting of
a square array of cylindrical polyvinylchloride inclusions in air. This
phononic crystal exhibits positive, negative, or zero refraction depending
on the angle of the incident sound beam, leading to interesting applications
as acoustic beam-splitters and collimators.
The second part of the talk, will focus on using such phononic metamaterials
for thermal applications. Since phonons are the primary 'heat-carriers' in
non-metallic systems, we explore the possibility of suitably manipulating
the phononic band-structures and therefore controlling the thermal
properties of select PMs. In particular, based on our developed expertise
with manipulating (lower-frequency) acoustic properties of materials, we
briefly examine the ability of nanostructured PMs including patterned
graphene, and SiGe quantum dots to function as thermoelectric (TE) materials
(with diminished thermal conductivity) as well as thermal interface
materials (TIM- by enhancing thermal conductivity). Such systems have
immense technological applications in the semiconductor industry due to
their heat-harvesting abilities (when used as TE) and heat-conducting
properties (when used as TIM). (PDF) |
|
March 25 |
Host:
Christopher Ober, Material Sciences and Engineering, Cornell University
Presenter: Christine Ouyang, Materials Sciences and
Engineering, Cornell University
Topic Title:
"Green
Processing in Photolithography"
Abstract: The use of chemical solvents in today’s
microelectronic fabrication process has generated chemical waste that is not
only costly to dispose of but also harmful to the environment. It is
therefore desirable to develop an environmentally friendly process to
address this issue by employing alternative green solvents. Supercritical
carbon dioxide (scCO2) and silicone fluids (linear methyl
siloxanes) are proposed as environmentally friendly media for developing
photoresist images. Both solvents are non-toxic, not ozone-depleting, inert
under most processing conditions and can be easily recycled. In addition,
their unique physical properties, such as very low surface tension and
viscosity, can provide answers to the current lithography problems.
Therefore, they have the potential to prevent the pattern collapse in the
cases of high aspect-ratio features.
Although scCO2 is a poor solvent for most
polymers, certain fluorine-and silicon-containing reagents make it possible
to dissolve those polymers in scCO2. Recently, we have shown that
negative-tone resist images down to 100 nm regime can be developed in scCO2
using conventional photoresists with the aid of fluorinated quaternary
ammonium salts (QAS). However, the incorporation of fluorine moieties into
photoresist processing poses environmental concerns. In our continuous
effort to make lithography process more environmentally benign, we have also
accomplished non-fluorinated molecular photoresists which still have the
processability in scCO2. In addition to scCO2, we are
studying silicone solvents as another type of green solvents for
photolithography. Silicone fluids have already been used in cleaning
applications and water removal steps in microelectronic fabrication. Here we
also demonstrate the capabilities of silicone solvents as versatile process
media for photolithographic processing. (PDF) |
|
April 8 |
Host: Srini
Raghavan, Materials Science and Engineering, University of Arizona
Presentation by:
Dr. Anoop
Agrawal, President , AJJER LLC, Tucson AZ
Topic title: "High throughput analysis of
environmental samples - A case study for analyzing beryllium"
Abstract: Environmental
analysis is done using conventional methods, where each sample is prepared
separately and analyzed. Higher efficiency has been introduced using
automated instrumentation where a large number of samples are grouped and
analyzed sequentially. However, sample preparation is still laborious, and
the sequential automation of sample analysis occupies the instrumentation
for long periods, thus limiting the throughput and increasing the analytical
cost. On the other hand, high throughput sample preparation and analysis is
used routinely by biologists. Typically such analysis is done in massive
arrays. This presentation discusses an interesting combination of high
throughput sample preparation and analysis for analyzing beryllium
particulates. In addition to increasing throughput, these methods reduce
work related injuries, improve worker safety and reduce cost by reducing
labor, capital and materials used. (PDF) |
| April 22 |
Host: Steven Nielsen,
Department
of Chemistry, University of Texas at Dallas
Presentation by:
Ruhung Wang, Bionanoscience Group at the University of Texas at Dallas
Topic title: "Physical
characterization and in vitro toxicity testing of commercially purchased
single-walled carbon nanotubes (SWNTs)"
Abstract:
Varieties of single-walled carbon nanotubes (SWNTs) synthesized by
different methods and with different functional modifications are offered
by a large number of vendors. There are no standards for characterizing
the properties and purity of commercially available SWNTs and information
about the SWNTs provided by vendors is often incomplete and sometimes
erroneous. In addition, vendors rarely provide information on potential
SWNT toxicity. Presented in this talk is a standardized set of physical
and chemical methods for characterizing commercially obtained SWNTs. The
rationales behind the approaches are discussed, and the results of
characterizing SWNT products are presented. In addition, a standardized
protocol for testing the toxicity of SWNTs in a model mammalian cell
culture system is presented. Interestingly, only one of the products we
tested so far was toxic to mammalian cultured cells, and we demonstrated
that the toxic material could be removed from the SWNTs. (PDF) |
| May 6 |
Host:
Reyes Sierra, Department of Chemical and Environmental Engineering,
University of Arizona
Presentation by:
Citlali Garcia, Postdoctoral researcher, Department of Chemical and
Environmental Engineering, University of Arizona
Topic title:
“Developing a Yeast Cell Assay for Measuring the
Toxicity of Inorganic Oxide Nanoparticles “
Abstract:
Short-term in vitro toxicity testing
protocols can be used for screening nanoparticle (NP) toxicity. Some
toxicity protocols that measure NP toxicity have been criticized
because of NP interference in the spectrophotometric or fluorescent
measurements utilized in the assays. The goal of this study was to develop
an assay free of interference utilizing Saccharomyces cerevisiae as a
unicellular eukaryotic model organism for toxicological evaluation. There is
currently little data about the toxicity of NPs to S. cerevisiae.
The parameter of measurement selected was the uptake of oxygen (O2)
which is not subject to interference by the presence of NPs. Various
inorganic oxide NPs were exposed to S. cerevisiae and their impact on
the rate of O2 uptake was measured. Non-toxic dispersing agents
were utilized to properly maintain the inorganic oxide NPs in dispersion in
the media used for the assay. This presentation discusses results of the
characterization of NPs and the O2 uptake by yeast. It also
compiles some data of inorganic oxide NPs toxicity to yeast in the absence
and the presence of dispersant. (PDF) |
| May 20 |
Host: Ara Philipossian,
Chemical and Environmental Engineering, University of
Arizona
Presentation by: Yun Zhuang, Chemical and Environmental Engineering,
University of Arizona
Topic titles:
Part 1: Effect of Pad
Micro-Texture on Frictional Force and Removal Rate during Copper CMP Process
****
Part 2:
Method for Ultra-rapid Determination of the Lubrication Mechanism of CMP
Processes
Abstracts:
Part 1:
In this study,
the effect of pad micro-texture on frictional force and removal rate during
copper CMP process was investigated. Blanket 200-mm copper wafers were
polished with Hitachi Chemical HS-2H635-12 slurry and frictional force was
measured in real-time during polishing. Two diamond discs (3M A2810 diamond
disc and Mitsubishi Materials Corporation (MMC) 100-grit diamond disc with
triple ring dot (TRD) design were used to condition an IC1010 M-groove pad
with Suba IV sub-pad under the conditioning force of 6 lb during wafer
polishing. For each diamond disc, eight blanket copper wafers were polished
at 1.5 PSI and 1.2 m/s to confirm the experimental reproducibility. For each
diamond disc, a pad sample was taken after wafer polishing. Pad surface
contact area and topography were analyzed using a Zeiss LSM 510 Meta NLO
laser confocal microscope. In addition, SEM analysis was performed on the
pad surface. During blanket wafer polishing, the average coefficient of
friction (COF) of the MMC disc (0.51) was lower than the 3M disc (0.59). In
addition, the average removal rate of the MMC disc (2,457 A/min) was
significantly lower than the 3M disc (3,415 A/min). By examining the pad
contact area images and surface topography images, it was found that the MMC
disc generated much larger flat near contact areas (indicated by zebra
patterns) that corresponded to pore walls that had been fractured and
collapsed. The fractured and collapsed pore walls partly covered the
adjacent pores, making the pad surface more lubricated and rendering a lower
COF and lower removal rate for the MMC diamond disc.
Part II: In CMP, as a first
approximation, the Stribeck curve helps provide evidence of the extent of
contact among wafer, pad and abrasive particles where three major
lubrication modes can be distinguished. The first mode is ‘boundary
lubrication’ where all solid bodies are assumed to be in intimate contact
with one another. In this case (which is preferable in CMP) the coefficient
of friction (COF) does not depend on the Sommerfeld number. The second mode
is ‘partial lubrication’ where the wafer and the pad are partially
contacting each other. Finally, the ‘hydrodynamic lubrication’ mode occurs
when the fluid film layer separates the pad and the wafer, and COF once
again becomes independent of the Sommerfeld number, albeit at a much lower
value. In practice, the Stribeck curve can help in screening certain
consumable sets (i.e. pad, slurry, wafer, retaining ring and conditioner
disc) by determining if and how they contact one another during CMP and can
help in determining the optimal polishing parameters (i.e. wafer, retaining
ring and diamond disc pressure, as well as slurry flow rate and tool
kinematics). Traditionally, constructing the Stribeck curve for a given
consumables set involves calculating the COF (by knowing the fixed down
force and by measuring the shear force in real-time). Since a wafer needs to
be polished to obtain the COF at a given polishing pressure and sliding
velocity, constructing the Stribeck curve requires polishing wafers at
various pressures and sliding velocities (as many as 20 polishing runs are
required in most cases) which is quite costly and time consuming. In this
study, a new method is presented to obtain the Stribeck curve corresponding
to a set of consumables in CMP by only performing one wafer polishing
experiment. This new method, which is also more accurate and cost effective,
is accomplished by use of polishers capable of simultaneously measuring
shear force and down force, and rendering a value for COF while
simultaneously enabling a multitude of changes in pressure and velocity in
real-time. In a given run, pressure and sliding velocity are varied
separately or together for a desired length of time so that multiple
measurements can be taken within one run. This presentation also discusses
several Stribeck curves resulting from various polishing substrates (blanket
copper and silicon dioxide wafers) using different types of polishing
slurries and pads (Cabot Microelectronics Corporation D100 concentrically
grooved pad, Dow IC1000 K-groove pad, and Dow IC1020 M-grooved pad).
(PDF_Part
1) (PDF_Part
2) |
| June 3 |
Host: Farhang Shadman,
Chemical and Environmental Engineering, University of Arizona
Presentation by: Dr. Jun Yan and Davoud Zamani, Chemical and
Environmental Engineering, University of Arizona
Topic title:
In-Situ and
Real-Time Metrology during Cleaning, Rinsing, and Drying of Micro- and Nano-Structures
Abstract: As semiconductor fabrication moves to
22 nm technology or beyond, two important questions have been asked about
surface preparation processes. First, can we clean the smaller nano features
using current surface preparation technologies? Second, can we clean small
nano feature and use less water and energy? To address these questions, we
needed a metrology technology to in-situ monitor the cleanliness inside nano
structures; hence, the Electro-Chemical Residue Sensor (ECRS) technology was
developed. In this seminar we will introduce the ECRS technology and its
applications to both batch tools and single wafer tools for surface
preparation. (PDF) |
| June 17 |
Host:
Anthony Muscat, Chemical and Environmental Engineering, University of Arizona
Presentation by: Shawn Miller, Chemical and
Environmental Engineering, University of Arizona
Topic title: "Improvements for silane based self-assembled
monolayers"
Abstract:
Self-assembled monolyers, SAMs, allow for selective
chemical patterning and selective growth of various materials, preventing
material deposition in undesired areas. The defect mechanisms which occur in
these self-assembled monolayers have been defined and treated. The primary
causes of deactivation failure for atomic layer deposition, ALD, growth
process are non-uniform grain boundaries between forming SAM islands, and
polymerized SAM molecules physiosorbed on the surface. By using a uniformly
hydroxylated Si starting surface, as well as removing any un-reacted or
polymerized molecules with a repeated molecular extraction process. The
result is a reduction in the SAM formation time scale from 48hrs to only
4hrs. With these improvements octadecyltrichlorosilane, OTS, SAMs have also
shown good chemical resistance to dilute aqueous acid and base solution, as
well as the TiO2 ALD process. The range of chemical solutions in which the
SAM is unaffected offers a wide variety of surface chemical patterning
options. (PDF) |
| July 1 |
Host: Jim Farrell,
Chemical and Environmental Engineering, University of Arizona
Presentation by: David Hubler, Graduate Research
Assistant, Chemical and Environmental Engineering, University of Arizona
Topic title:
"Treatment of Copper-CMP Wastewater"
Abstract:
Chemical mechanical planarization (CMP)
operations account for almost thirty percent of the total water used in
semiconductor manufacturing. This research investigated several unit
operations that could be applied for treating CMP wastewater. The primary
contaminants examined were hydrogen peroxide, organic chelating agents and
copper ions. Simultaneous hydrogen peroxide destruction and organic
compound oxidation were investigated using ultraviolet (UV) light, ozone,
activated carbon and a manganese dioxide catalyst. The manganese dioxide
catalyst was the most effective for hydrogen peroxide destruction, but
removed very little of the organic compounds. UV light and ozone were
effective at removing the organic compounds, but the kinetics for hydrogen
peroxide removal were too slow to utilize in a practical treatment process.
An electrochemical process for regenerating copper saturated ion exchange
media was developed. This process recovers the copper and does not produce
a brine stream requiring further treatment or disposal. A cost analysis
suggests that CMP wastewater can be economically reclaimed as a feed stream
for the production of ultrapure water. (PDF) |
| July 15 |
Host: Srini Raghavan,
Materials Science and Engineering, University of
Arizona
Presentation by: Manish Keswani, Asst. Research Professor,
Materials Science and Engineering, University of Arizona
Topic title:
"Effect of Dissolved Gases on Sonoluminescence
Signal from Aqueous Solutions Irradiated with Megasonic Energy"
Abstract:
Megasonic cleaning is routinely employed in
semiconductor industry for removal of particles during cleaning of wafers.
However, use of megasonic energy also results in damage to wafer features
and the extent of damage has been shown to correlate with sonoluminescence
(SL) intensity. In the first part of the presentation, development of a
portable, UV light tight, cavitation threshold cell (CT Cell) for
measurement of SL, under precisely controlled conditions, will be described.
In the second part of the presentation, effect of dissolved gases such as O2,
N2, Ar and CO2 in deionized water will be discussed.
Key experimental variables investigated were megasonic power density, duty
cycle and concentration of dissolved gases. Two novel chemical methods to
control SL through in situ consumption of O2 or release of CO2
in aqueous solutions have been developed. While an increase in dissolved
oxygen increases SL, addition of carbon dioxide has been found to be inhibit
SL. (PDF) |
| July 29 |
Host: Christopher Ober,
Materials Science and Engineering, Cornell University
Presentation by:
Marie Krysak ,
Materials Science and Engineering, Cornell University
Topic title:
“PVD Resists:
Environmentally friendly resists using physical vapor deposition”
Abstract: Physical Vapor Deposition (PVD) is a
promising method of photoresist deposition. This solvent-free process
fabricates thin layers with a precise thickness and a defined layer
composition. PVD offers an environmentally friendly alternative over
solvent casting, as there is a significant reduction of resist waste and no
solvent is used during the process. In order for materials to be considered
for PVD, they must have a low molecular weight, good thermal stability and
have the ability to form amorphous films. Molecular glasses are a class of
low molecular weight amorphous compounds that possess all of the necessary
characteristics for use in PVD. Libraries of compounds have been
successfully vapor deposited onto silicon wafers. PVD has shown advantages
over solvent casting because of the ability to create composition gradients
to efficiently screen compounds for use as photoresists. All-dry lithography
will also be discussed and a completely solvent free method of patterning
photoresists. All-dry lithography combines the use of PVD and vacuum
development to eliminate the use of solvent in the lithography process,
which drastically reduces waste generated by patterning semiconductors. (PDF) |
| Aug. 12 |
Host: Farhang
Shadman, Chemical and Environmental Engineering, University of Arizona
Presentation by: Dr. Jean-Francois Robillard, Research
Associate, Materials Science and Engineering, University of Arizona
Topic title:
"Exciting and
detecting waves in micro and nanoscale systems by Picosecond Ultrasonics"
Abstract:
Picosecond Ultrasonics is an
optical pump-probe technique capable of exciting and detecting acoustic
waves in the hypersonic frequency range (GHz - THz). It is an established
technique and over the past two decades has become an important method in
basic solid state physics research as well as for the characterization of
sub-micron thin films. Specifically, properties such as thickness, sound
velocity, density, and adherence can be determined using this technique.
Recently, Picosecond Ultrasonics has received attention due to its potential
applications for the investigation of acoustic properties of nano-objects.
Towards this end, experiments were conducted on lattices of various metallic
nanocubes. Two kinds of acoustic modes were demonstrated: the individual
modes of the cubes and modes that originate from the collective behavior of
the cubes. These collective modes, reported here for the first time, were
studied as a function of the lattice constant. Analysis and modeling have
shown that their frequency strongly depend on the geometry and elastic
properties of the system. These results demonstrate the broader
applicability of Picoseconds Ultrasonics for a true 3D characterization of
the structure-properties relations of complex materials. (PDF) |
| Aug. 26 |
Host: Jim Field, Chemical and
Environmental Engineering, University of Arizona
Presentation by: Francisco Gomez, Chemical and
Environmental Engineering, University of Arizona
Topic title: "Removal of Cerium Oxide Nanoparticles from
Wastewater by Activated Sludge Treatment"
Abstract: The rapid increase in the application of engineered
nanomaterials (ENM) indicates the need to address the safety implications of
these materials. Nano-sized inorganic oxides such as silica (SiO2),
ceria (CeO2), and alumina (Al2O3) are used
in many industrial processes, including catalysis, polymers, coatings and
semiconductor manufacturing. These three inorganic oxides are on the OECD
list of priority nanomaterials for immediate testing. The stability of
nanosized oxide dispersions in sewage is likely to be altered due to the
significant changes in the water chemistry (e.g., circum-neutral pH values,
high concentrations of organic matter, reduced levels of surfactants, etc.),
which might result in particle agglomeration and eventually even
sedimentation. In addition to particle agglomeration and gravitational
settling, interactions of NPs with microorganisms involved in biological
wastewater treatment might be an additional mechanism contributing to the
removal of abrasive NPs. Unfortunately, information on the stability of
nanoparticles in wastewaters is very scarce.
The objective of this research is to investigate the fate of CeO2
nanoparticles during municipal wastewater treatment and elucidate the main
mechanisms contributing to their (partial) removal. The study was conducted
in a laboratory-scale activated sludge system (A/S) fed with municipal
wastewater collected from a local treatment facility and a nano-sized CeO2
dispersion (average particle size = 50 nm). Continuous bioreactor
experiments were also conducted with a well-defined synthetic wastewater to
study the contribution of specific wastewater components to NP (de)stabilization.
(PDF) |
| Sept. 9 |
Host: Alex Tropsha,
Division of Medicinal Chemistry
and Natural Products,
UNC Eshelman School of Pharmacy,
University of North Carolina at Chapel Hill
Presentation by:
Bing Yan, Ph.D.,
Member,
Department of Chemical
Biology and Therapeutics,
St. Jude Children's
Research
Hospital
Topic title: "Reducing
Nanotoxicity with Nano-Combinatorial Chemistry Approach:
The Case of Carbon Nanotube"
Abstract:
Carbon nanotubes (CNTs) could bind biomolecules, penetrate membranes, and
induce toxicity in cells, organs, and animals. Chemical modifications of the
large CNTs surface may have a major impact on their biological/toxicological
activities. To test this hypothesis, we designed and synthesized a CNT
library using combinatorial chemistry approach and tested the effects of
such modifications on CNTs regarding their protein bindings and cellular
toxicities. Results showed that surface chemistry diversity can effectively
reduce CNT’s interactions with proteins as well as their cytotoxicity. The
experimental data was subjected to computational analysis by Alexander
Tropsha’s group using chemoinformatics approaches. Each CNT was represented
by a single copy of its surface molecule which was then encoded by chemical
descriptors. Structure-activity relationship (SAR) analysis enabled us to
identify substructures (fragments) of surface-modifying chemical structures
that would lead to reduced protein binding profile and cellular toxicity.
Quantitative SAR (QSAR) models were developed using the experimental data
described above. These models can discriminate strong versus weak protein
binders, as well as strong versus weak cellular toxicants, with the overall
prediction accuracy as high as 74%. These results suggest that we should be
able to rationally design biocompatible surface-modified CNTs using a
combination of experimental and computational approaches. (PDF) |
| Sept. 23 |
Host: Jim Field, Chemical and
Environmental Engineering, University of Arizona
Presentation by: Antonia Luna, Chemical and
Environmental Engineering, University of Arizona
Topic title:
“Oxidation
of a Reactive Oxygen Species (ROS) Indicator Dye by Inorganic Nanoparticles”
Abstract:
Numerous
reports published in recent years indicate a growing concern for the
potential toxicity of engineered nanoparticles (NPs). Study of the
potential risk of NPs is a top priority for the semiconductor industry due
to the fact that some inorganic NPs (e.g., CeO2, Al2O3,
SiO2 etc.) are currently used in its manufacturing processes.
Recently toxicity studies have hypothesized several NP toxicity mechanisms,
such as catalytic interaction, solubilization, and increased production of
reactive oxygen species (ROS), such as superoxide (·O2‒),
hydrogen peroxide (H2O2), and hydroxyl radical (·OH).
Numerous studies suggest that a common mechanism of NP toxicity is via
oxidative stress by ROS which are strong oxidants that react rapidly with
most biological molecules. That finding suggests that the toxicity of NPs
might be predicted from their ROS generating capability in vitro. The aim
of this research is to determine if the chemical reaction of NPs with
dissolved oxygen or with other biological molecules (e.g., phenolic
compounds susceptible to oxidation such as catechol and L-dopa) can cause
formation of ROS. This was tested with a ROS-sensitive dye, 2′,7′-
dichlorodihydrofluorescein (DCFH), which is oxidized to its highly
fluorescent product 2′,7′-dichlorofluorescin (DCF) in the presence of ROS.
We found that most inorganic NPs assayed reacted with L-dopa and dissolved
oxygen enhancing ROS production. Nano-sized Mn2O3
could cause direct oxidative reaction with DCF without dissolved oxygen or
L-dopa, which may indicate its potential to directly oxidize certain cell
components. Experiments with electron paramagnetic resonance (EPR) analysis
are currently being performed to confirm and identify the ROS species formed
by the NPs studied. (PDF) |
| Oct. 7 |
Host: Srini Raghavan,
Materials Science and Engineering, University of
Arizona
Presentation by:
Joel Barnett,
SEMATECH
Topic title:
“Wet
processing techniques for achieving ultra-shallow junctions
in future CMOS devices”
Abstract:
In the
integrated circuit industry, ion implantation has long been the predominant
doping technique. Current Ultra-shallow junctions (USJs) in Si are
fabricated by a combination of ion implantation and spike annealing. In
this presentation, a novel wet processing based method for creating USJ's
known as Monolayer doping (MLD), will be discussed. Benefits of and
barriers to implementation of this method will also be discussed. (PDF) |
| Oct. 21 |
Host: Yoshio
Nishi, Professor of Electrical Engineering and Director, Stanford Nano
Fabrication Facility, Stanford University
Presentation by: Gaurav Thareja, Electrical Engineering,
Stanford University
Topic title: "Surface Passivation and Characterization
of Ge Channel Field Effect Transistor together with Source/Drain
Engineering"
Abstract: Germanium (Ge) has emerged as an important
materials platform during recent years. With its high carrier mobility and
the ability to detect and emit photons at telecommunications wavelengths, Ge
is an attractive candidate for applications in both high
performance electronics and optoelectronics. Moreover due to its
compatibility with conventional CMOS fabrication, it can be processed using
the standard manufacturing techniques that are currently used for silicon.
However Ge does present a number of unique challenges that must be overcome,
including issues of surface passivation, low n-type dopant solubility, and
high dopant diffusivity.
In this talk, I will present my work summarizing three
different contributions to Ge MOS technology:
(1) Surface passivation of Ge by ultra-thin
GeO2 interfacial layer. This is processed using Slot Plane Antenna (SPA)
radical oxidation which provides substrate orientation independent growth
rate of GeO2 and reduced interface state density.
(2) Ultra Shallow Junctions (USJ) for
Ge using Plasma Immersion Ion Implantation (P-III).
(3) High n-type dopant activation
using Laser Thermal Processing (LTP). (PDF) |
| Nov. 4 |
Host: Farhang Shadman,
Chemical and Environmental Engineering, University of
Arizona
Presentation by: Jeff Rottman
and Hao Wang, Chemical and
Environmental Engineering, University of Arizona
Topic title:
Rottman:
"Transport of Nanoparticles in Porous Media"
Wang:
"Physicochemical and Surface Characteristics Study of Nanoparticles related
to ESH Impact of Emerging Nanoparticles and Byproduct in Semiconductor
Manufacturing"
Abstract:
Rottman:
The use of nanoparticles in semiconductor
manufacturing continues to increase, thus raising concerns over their
potential environmental and health effects. Understanding the transport of
these nanoparticles in porous media has implications in both their fate in
the environment as well as the development of novel treatment technologies.
The current understanding of the transport mechanisms will be reviewed.
Additionaly, we will introduce our design to model simultaneous aggregation
and deposition of nanoparticles in porous media.
Wang: Environmental Safety and
Health impact of nanoparticles has been studied for years, since
nanoparticles have been widely used in semiconductor manufacturing.
Nanoparticles with high surface area can easily adsorb toxic chemicals,
which promote their toxicity. Physicochemical and surface characteristics of
different nanoparticles, such as SiO2, HfO2, and CeO2, have been studied by
moisture adsorption and desorption. The result shows species effect and size
effect on characteristics study. A transient adsorption and desorption model
has been applied to study the surface characteristics of different
nanoparticles. Compared with the experimental data, the model could tell
surface available sites, adsorption and desorption coefficients of
nanoparticles. It also indicates a transient moisture adsorption and
desorption process on nanoparticles. Moreover, this model could predict size
effect and different contamination adsorption and desorption on various
nanoparticles. (PDF-Rottman) (PDF-Wang) |
| Nov. 18 |
Host: Yongsheng Chen, School of Civil and
Environmental Engineering, Georgia Institute of Technology
Presentation by:
Jonathan D. Posner, Chemical Engineering, Mechanical Engineering, Arizona
State University
Topic title:
"Using
Nanoparticle Interaction with Lipid Bilayers as a Global Descriptor for
Prediction of Bioavailability and Toxicity"
Abstract:
Quantitative structure-activity relationships (QSARs) relate the
physicochemical characteristics of NPs to their biological toxicity and have
the potential to predict the toxic effects and bioaccumulation of existing
and future engineered NPs used in semiconductor industries. NP toxicity and
bioaccumulation are typically measured by a series of in-vitro cell culture
protocols and by animal exposure tests. Investigating the relationships
between the toxicity and bioaccumulation of NPs and their physicochemical
properties (composition, size, geometry, charge, and molecular structure) is
a significant step toward understanding and predicting potential risks of
nanomaterials. Although the QSAR model has been used successfully for
decades in classifying hazardous chemicals and for environmental risk
assessment, their use in predicting toxicity and bioaccumulation of NPs is
relatively new due to the lack of physicochemical data required to create a
useful model.
Considering the wide range of nanoparticles’ properties
and diversity of animal and in-vitro models, it is challenging to map the
detailed physiochemical properties of nanoparticles to the empirical
bioaccumulation and toxicology studies. For organic contaminants, global
descriptors such as the partitioning between the organic solvent phases
(typically n-octanol) and water (KOW) has traditionally been used as an
empirical approach to evaluate the bioavailability (and from this infer
toxicology) of organic pollutants and is used extensively in current EPA
models.
In our work, we aim to develop analogous global
descriptor methods for predicting bioaccumulation and toxicity of
nanoparticles that account for the collective influence of nanoparticle
properties, in a similar way as KOW depends upon multiple parameters of
organic pollutants (molecular weight, conformation, hydration states, ionic
charge, etc). In this talk we quantify nanoparticle’s lipid-water
distribution coefficients and disruption of bilayers and use them as a
global descriptor that captures the critical interactions between
nanoparticles and biological interfaces which may be used to predict their
bioaccumulation and toxicity potential. (Presentation may be requested
from author; contact: |
| Dec. 2 |
Host: Reyes
Sierra, Chemical and Environmental Engineering, University of
Arizona
Presentation by:
Lila Otero, Chemical and Environmental Engineering, University of Arizona
Topic title: "Comparison of Nanoparticle Toxicity to Yeast
Cells and Human Lung Epithelial Cells"
Abstract: The semiconductor manufacturing industry is
already using nanoparticles (NPs) of SiO2, Al2O3
and CeO2 in the chemical mechanical planarization process.
Additionally, a wide variety of NPs are being considered for emerging
processes in the industry. Due to their small dimension, and higher
reactivity, there is growing public concern that nanoparticles may have a
higher toxicity to cells compared to bulk particles. Initial NP toxicity
testing utilizing dyes in colorimetric based tests resulted in artifact
effects. Therefore, there is a great need to develop toxicity tests less
prone to interferences. Likewise there is a need to have high through-put
toxicity screening. In this study, the toxicity of NPs was compared in two
newly developed tests. One test was a yeast toxicity test based on measuring
the rate of O2 uptake. The second test is a high through put real
time cell proliferation test which measures the impedance of electrodes
placed at the base assay wells. The instrument utilized for the latter test
is an xCELLigence System (Roche) which can handle 576 wells in a single run
and it was tested with a human lung epithelial cell line. The testing
identified ZnO, Ag0 and Mn2O3 as examples
of the most toxic NPs; whereas many of the other NPs tested had mild or no
toxicity. A preliminary study of mechanisms of toxicity was also conducted
by measuring damage to cell membranes, NP dessolution potential of and role
of NPs in forming reactive oxygen species. (PDF) |
| Dec. 16 |
Host: Duane
Boning,
Electrical
Engineering and Computer Science, Massachusetts Institute of Technology
Presented by:
Wei Fan, Department of Electrical Engineering and Computer Science, MIT
Topic title:
"Characterization and Modeling of CMP Pad Asperity Properties"
Abstract:
In chemical-mechanical polishing (CMP), reduction in the usage of
consumables including the polishing pad and slurry, together with
improvement in yield and planarization performance, are needed for future
technologies. In this work, we are seeking to understand the role of the
polishing pad surface in efficient planarization: the pad modulus and
asperity height are two important properties which affect the planarization
results. Physical measurements of pad asperity modulus (by nanoindentation)
and asperity height (by micro profilometry) are performed on sample pads.
Pad aging effects are tested by comparing the measured results from the same
location on a pad after different polishing times (initial, 8 hours and 16
hours). Pad property uniformity is investigated by comparing the measured
results from different locations on the pad after 16 hours polishing. To
understand the interactions between CMP pad asperities and the wafer, a
physical model is proposed; pad asperity modulus and height distribution are
included in the model. The measured results can be used in the model to
predict the contact area percentage between the pad and wafer in the CMP
process, providing information about localized pressures and resulting
planarization performance. (PDF) |
|
Dec. 30 |
No TeleSeminar
|
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