|
| |
| -
2009 - |
| Jan.
8 |
No
TeleSeminar |
| Jan. 22 |
No
TeleSeminar |
| Feb. 5 |
No
TeleSeminar |
Feb. 12
(inserted interim date) |
Host: Farhang
Shadman, Chemical and Environmental Engineering, University of Arizona
Presentation by: Professor David Lynch, Materials
Science and Engineering, University of Arizona and Chief Technical
Officer, Solar Technology Research Corporation, Tucson, Arizona
Topic title: "Winning the
Global Race for Solar Silicon"
Abstract: The status of players in the race to produce low
cost solar silicon is reviewed, with emphasis on their chemistries, and cost
predictions. The first shortage of silicon for the photovoltaic industry
occurred in 1996/97 with the price of silicon rising by a factor of 3 to a
high of $75 per kg on the spot-market. The shortage disappeared with the
“dot-com” crash, only to reappear in 2004. That shortage continued through
2008, with the spot market price rising to a high of $ 400 per kg. In 2006
the demand for electronic grade silicon (e-Si) for photovoltaics exceeded
that for the electronic industry. Producers of e-Si have been slow to
react to market conditions, primarily due to the vagaries of government
support for solar energy and the capital cost associated with constructing
new Siemens refining facilities. These conditions, although eased by
recent economic developments, are likely to continue given the current
administrations desire to decrease the country’s dependence on foreign
energy sources, and have lead both major companies and startups to seek new
low cost routes for producing solar silicon. (PDF) |
| Feb.
19 |
No
TeleSeminar >> ERC Review Meeting
February 19-20, 2009 |
| March
5 |
No
TeleSeminar |
| March 19 |
No
TeleSeminar |
| April 2 |
No
TeleSeminar |
| April 16 |
Host: Jim Field, Chemical and Environmental
Engineering, University of Arizona
Presentation by: Paul Pantano,
Associate Professor of
Analytical Chemistry, U.Texas Bionanosciences Group, University of Texas/Dallas
Topic title:
"Challenges in Assessing the Potential Cytotoxicity of Carbon Nanotubes"
Abstract: There are conflicting reports in the
literature regarding the toxicity of carbon nanotubes (CNTs). This
seminar will address the main reasons for the poor agreement and present
our solutions. First, we will emphasize the importance of thoroughly
characterizing CNT materials before cytotoxicity assessments are offered.
Second, we will present our standard protocol for assessing the potential
cytotoxicity of CNTs. Third, we will introduce a rapid, inexpensive, and
label-free method to measure nanogram amounts of CNTs in liquid samples.
Next, we will demonstrate how this method can determine the amount of CNTs
associated with biological cells, and the importance of such information
in generating more useful cytotoxicity reports. Finally, we will discuss
how this new analytical method can be applied to the at-line analysis of
CNTs and other nanoparticles from a process waste stream. (PDF) |
| April 30 |
Host: Jim Field,
Chemical and Environmental Engineering, University of Arizona
Presentation by: Alex Tropsha and Denis Fourches, Division of Medicinal
Chemistry & Natural Products, University of North Carolina/Chapel Hill
Topic title: "(Challenges of) Computer-Aided Nanotoxicology"
Abstract: Evaluation of various biological effects of
Manufactured Nanoparticles (MNPs) is of critical importance for
nanotechnology. Experimental studies (especially, toxicological) are
time-consuming, costly, and impractical calling for the development of in
silico approaches. We have begun to develop
Quantitative Nanostructure – Activity Relationships (QNAR) models where
physical/chemical/geometrical properties of the MNPs such as composition,
size, shape, aspect ratio, surface area, chemistry/morphology, zeta
potential, chemical reactivity, etc. could be used as MNPs’ descriptors.
Using data recently obtained from in-vitro cell viability assays (PNAS,
2008, 105, pp 7387-7392; Nat. Biotechnol., 2005, 23, pp 1418-1423) we have
developed QNAR with strong external predictive power. Similar to
conventional applications of QSAR modelling for the analysis of organic
biomolecular datasets, these models can be used to predict activity profiles
of newly designed nanomaterials and bias the design and manufacturing
towards better and safer products. (PDF) |
| May 14 |
Host: Jim
Field, Chemical and Environmental Engineering, University of Arizona
Presentation by: Buddy Ratner, Department of
Bioengineering and Department of Chemical Engineering, University of Washington
Topic title:
“Static SIMS: A Powerful Tool to
Investigate Nanoparticles and Biology”
Abstract: Static secondary ion mass spectrometry
(SIMS) is an exceptionally powerful characterization tool, with much
applicability to issues that the semiconductor industry must address. Static
SIMS capabilities include exceptionally high analytical sensitivity, spatial
information in the x,y plane in regions as small as 50 nm x 50 nm, surface
analysis of the outermost 1 nm zone, the ability to depth profile down
through materials, unambiguous identification of all elements and high mass
resolution identification of organic molecules. The basic principles of SIMS
will be introduced. The applicability of the static SIMS method to study
contaminants on nanoparticles and also to learn about cells on surfaces will
be demonstrated. The use of mathematical tools (multivariate statistical
methods) such as principal components analysis (PCA) help us to extract
useful information from the huge data sets produced by SIMS. (PDF) |
| May 28 |
Host: Jim
Field, Chemical and Environmental Engineering, University of Arizona
Presentation by: Yongsheng Chen, Department of Civil and
Environmental Engineering, Arizona State
University
Topic title: "Evaluation of Bioaccumulation and Toxicity
of Nanopariticles using Aquatic Organisms"
Abstract: Nanoparticles (NPs) have enhanced mobility
and, potentially, greater toxicity as they have almost unrestricted access
into aquatic organisms and the human body due to their size and specific
surface areas. However, there is few data available on whether NPs are toxic
within months or years. So, these NPs could constitute a new class of
non-biodegradable pollutants and may bioaccumulate in the food chain.
Consequently, it is imperative to evaluate the potential risks of
bioaccumulation of NPs in aquatic organisms so that we can understand their
potential impacts and avoid serious environmental consequences. In this
study, four aquatic organisms (algae, daphnia, and zebra fish/carp) were
selected. The bioavailability, bioconcentration, bioaccumulation, and
toxicity of above-mentioned aquatic organisms were tested by exposure to
various NPs, including metal oxides, C60, single-walled carbon nanotubes (SWCNTs),
and muti-walled carbon nanotubes (MWCNTs). Genomic and advanced analysis
techniques such as zetasizer, transmission electron microscopy (TEM), ICP-MS,
and flow cytometry were employed to determine size, concentration, tissue
distribution, cellular effects, reactive oxygen species (ROS) of NPs. (PDF) |
| June 11 |
Host: Bert Vermeire, Department of Electrical Engineering, Arizona State
University
Presentation by: Greg Raupp, Professor of Chemical
Engineering, Arizona State
University
Presentation title: ESH Challenges and
Opportunities in Large Area High Tech Manufacturing: Displays, Thin
Film Photovoltaics, Solid State Lighting, and Flexible Electronics
Abstract: Environment, Safety and Health
manufacturing challenges in the maturing flat panel display industry and the
emerging thin film photovoltaic, solid state lighting and flexible
electronics industries are strikingly similar to those encountered in
microelectronics manufacturing. In this context many of the philosophies,
approaches and techniques successfully under development or adopted in the
semiconductor industry can be leveraged to achieve success in this arena.
In this talk the analogies between the industries will be highlighted, along
with their differentiating features.
In contrast to the semiconductor industry, these high tech industries
fabricate their products on quite large substrates (e.g., as large as
2m x 3m) and the products themselves can be quite large (witness a 70-in
diagonal LCD TV). A substantial cost of manufacturing in the materials
themselves. These characteristics lead to substantial opportunities for
cost savings and environmental benefit through ESH strategies that enhance
materials utilization efficiencies or/and reduce process steps. Several
exemplary projects focused on sustainable large area manufacturing will be
described. (PPT) |
| June 25 |
Host: Anthony
Muscat, Chemical and Environmental Engineering, University of Arizona
Presentation by: Shawn Miller, Chemical and
Environmental Engineering, University of Arizona
Presentation title:
Low-ESH-impact Gate Stack
Fabrication by Selective Surface Chemistry
Abstract: An additive processing approach where material
is selectively deposited on a surface to build a device from the bottom up
could reduce the number of fabrication steps. Process flows with fewer steps
have the potential to minimize the costs for raw materials and energy as
well as the waste generated. On the front end of CMOS device fabrication,
one application is to deposit a high-k dielectric film selectively on
exposed gate channel areas relative to the surrounding masked regions. This
presentation reports a study on the use of hydrophobic, self assembled
monolayers (SAMs) to make surfaces chemically resistant to high-k dielectric
films deposited by atomic layer deposition (ALD). SAMs were formed on
hydroxylated Si(100) surfaces and exposed to TiO2 ALD. The
following SAM molecules were deposited: octadecyltrichlorosilane (OTS),
triacontyltrichlorosilane (TTS), triacontyldimethylchlorosilane (TDCS),
tridecafluoro-1,1,2,2-tetrahydrooctylsilane (FOTS), octadecyldimethoxysilane
(ODS), and trimethylchlorosilane (TMCS). Ellipsometry and goniometer
measurements showed a thickness of 26 ± 1Å and a contact angle of 110° ± 1°
after exposing a hydroxylated silicon dioxide to a 10 mM OTS in toluene
solution for 48 hour. Thus far OTS has outperformed all other SAMs. Exposure
to a 10mM TTS in toluene solution gave a water contact angle of 110° ± 5°,
but a thickness of 130 ± 10 Å. Using a 2mM TTS in toluene solution reduced
the thickness to 50 ± 2 Å after 48 hours. TDCS had a contact angle of only
80°± 20°. Rinsing with the organic solvents isopropanol, methanol, and
chloroform were compared. Chloroform was the most effective for each SAM.
TiCl4 and H2O were chosen as model precursors for
high-k dielectric films, and SAM surfaces were subjected to 50-500 cycles of
TiO2 ALD at 170°C. The stability of the SAM layers when exposed
to TiCl4 and H2O was monitored using the Ti and Si
x-ray photoelectron spectroscopy (XPS) peaks. TiCl4 appeared to
degrade the SAM layers, as shown by an increase in the Si peak area due to
exposing the substrate. There was no difference in the amount of Ti
deposited when SAMs were exposed to H2O for 20 s or baked out at
170°C for 24 hours before performing 50 cycles of ALD. Therefore, the SAM
did not absorb enough water during a 20 s water pulse to nucleate higher
growth, and the SAM should be equally resistant to water during the ALD
process. The results suggest that blocking strategies for TiO2
deposition from TiCl4 and water should focus on building a robust
SAM layer that is resistant to chemical attack by Cl. (PDF) |
| July 9 |
Host: Srini Raghavan, Materials Science & Engineering, University of Arizona
Presentation by: Jeff Butterbaugh, Chief Technologist,
FSI International
Topic title: "Steam-Injected SPM Process for All-Wet
Stripping of Implanted Photoresist"
Abstract: Photoresist stripping in IC
manufacturing has become an increasingly challenging process as the number
of photoresist levels has increased simultaneously with a decrease in
acceptable levels of material loss and surface damage. Heavily implanted
photoresist is especially challenging due to the tough layer of
dehydrogenated, amorphous carbon that forms on the surface. Implanted
photoresist can be removed by exposing the surface layer to the aggressive
chemical/physical action of a dry plasma ashing. This kind of physical
process, however, can lead to surface damage and increased material loss.
An alternative approach is to increase the reactivity of the sulfuric acid
–“ hydrogen peroxide mixture (SPM), so that it can penetrate and dissolve
the amorphous carbon layer and achieve complete photoresist removal. In a
novel approach, steam is absorbed by SPM at the wafer surface significantly
increasing the chemical temperature while avoiding excessive dilution.
(PDF) |
| July 23 |
Host: Duane
Boning,
Electrical
Engineering and Computer Science, Massachusetts Institute of Technology
Presentation by: Sarah Jane White, Civil and
Environmental Engineering, Massachusetts Institute of Technology
Topic title:
"The Rise of
III-V Semiconductors and Their Impact on Environmental Indium
Concentrations"
Abstract: New semiconductor manufacturing processes are
critical to emerging energy technologies. While these technologies will
inevitably employ the use of novel materials, potentially in large
quantities, little is known about the environmental behavior or toxicology
of many of the materials that will be employed. This work investigates the
potential impact of novel metals on the environment, using indium as a case
study. Indium production has been predicted to increase as much as
1000-fold in the next two decades, driven by its use in new high-efficiency
photovoltaic cells, LEDs, and in indium tin oxide (ITO) electrical coatings
for photovoltaics and displays (e.g. flat panel and liquid crystal
displays). We propose the comparison of anthropogenic fluxes to natural
fluxes of a metal as a useful early approach for flagging elements for
priority study if it appears that projected anthropogenic fluxes may rival
or exceed their natural fluxes. Presently, industrial releases of indium
exceed natural emissions. Mining and coal burning seem to dominate the
industrial releases, though the semiconductor industry has the potential to
rival these as indium use increases. We hypothesize that at present
production levels, use by the semiconductor industry may actually drive a
demand for indium that enhances its recovery from zinc ores (of which indium
is a byproduct) and decreases environmental releases. If demand for
indium expands enough to drive an increase in zinc mining, however, overall
releases of indium to the environment may also increase. A better
understanding of a metal’s natural and industrial cycling can lead to more
informed decisions about its environmental impacts and use in new
technologies. (PDF) |
| Aug. 6 |
Host: Reyes
Sierra, Chemical & Environmental Engineering, University of Arizona
Presentation by: Reyes Sierra, Chemical & Environmental
Engineering, University of Arizona
Presentation title: “Toxicity characterization of HfO2
nanoparticles”
Abstract: HfO2 nanoparticles are being considered for
application in immersion photolithography. The introduction of high-index
immersion fluids can allow optical lithography to be extended beyond the 45
nm node. Information on the EHS aspects of HfO2 nanoparticles is very
limited. This seminar will present the results of a research study conducted
to assess the potential cytotoxicity of HfO2 nanoparticles. The results
obtained indicate that detailed physico-chemical evaluation of the
nanoparticles, including surface characterization, is required to generate
useful cytotoxicity reports. (PDF) |
| Aug. 20 |
Host: Denis
Fourches, Laboratory for Molecular Modeling (MML)
and Alex Tropsha, Chair, Division of Medicinal Chemistry
and Natural Products, University of North Carolina-Chapel
Hill
Presentation by: John Elliott, Cell Signaling Systems
Group, NIST-Biochemical Sciences Division
Topic title: "The NIST NanoBioTox Working Group-Current and
Future Directions"
Abstract: Advances in nanotechnology are
revolutionizing the ability to design and manufacturer nanometer size
materials. Although these materials will have significant impact on the
character of new materials and medicines, it remains unclear how safe these
nanoparticle-based products will be for biological systems that may be
exposed to them. Discovering the structural and chemical rules that can
identify potential nanomaterial-related biohazards requires high quality
nanotoxicology and nano-cytotoxicology measurements. The NIST NanoBioTox
working group is a group of physicists, chemists, surface scientist,
material scientist and biologists working to assess measurement and
standards needs for nanotoxicology and nano-cytotoxicology testing. We are
currently focused on measurements of DNA damage and cellular response in the
presence of nanomaterials, and how nanomaterial dispersion procedures may
influence these results. Many members of the working group are also
involved in both national and international “nano” communities to facilitate
discussions about measurement needs in nanomaterial safety assessment. We
envision that these efforts will aid in the development of new standards and
technology for ensuring a reliable measurement infrastructure for toxicology
testing of nanomaterials. (PDF) |
| Sept. 3 |
Host:
Christopher Ober,
Department of
Materials Science and Engineering, Cornell University
Presentation by:
Jin-Kyun Lee,
Post Doctoral Fellow, Department of Materials Science and Engineering,
Cornell University
Topic title: "Orthogonal
Processing for Organic Semiconductor Devices"
Abstract:
Organic electronics is an extensively studied subject opening new horizons
in electronics technology. It has attracted great attention as a technology
to enable flexible electronic devices through solution processing of organic
materials. As with inorganic semiconductors, organic devices require active
functional materials to be tailored into micro-patterned and multi-layered
device components. While the former relies on photolithographic techniques,
organic devices are restricted from adopting those robust, high-resolution
and high-throughput patterning methods because of the chemical
incompatibility between organic materials and patterning agents. This
challenge has thus stimulated us to invent a non-damaging photolithographic
process for organic electronics.
In this research, we introduce a new imaging material and unique patterning
method, which utilizes environment/materials-friendly supercritical carbon
dioxide (scCO2) and segregated hydrofluoroether solvents (HFEs).
Since scCO2 and HFEs are poor solvents for common non-fluorinated
organic materials, they are highly promising media for the processing of
delicate organic electronic devices. In addition, HFEs are
environmentally-friendly thanks to their zero-ozone depletion potential and
short atmospheric lifetime, which is another important advantage of our new
method. An acid-sensitive semi-perfluoroalkyl resorcinarene, processable in
scCO2 and HFEs, was developed and evaluated under
photolithographic conditions. Its orthogonality to common organic materials
further enabled multilevel patterning as demonstrated by the fabrication of
overlaid patterns of organic electroluminescent materials. (PDF) |
| Sept. 17 |
Host: Scott Boitano, Associate Professor,
Physiology, Arizona Respiratory Center, University of Arizona
Presentation by: Scott Boitano, Associate Professor,
Physiology, Arizona Respiratory Center, University of Arizona
Topic title: "Measuring cytotoxicity of nanoparticles in
human cells"
Abstract: Engineered Nanomaterials (ENMs) are
increasingly being utilized in a variety of industrial processes and
consumer products with a notable lag in information on their health and
safety. There have been noted differences in the toxicity attributed to ENMs,
however, little progress has been made on elucidating specific
characteristics of ENMs that contribute to (or predict their) acute toxicity
or the long-term effects of ENM exposure. At the University of Arizona we
have assembled an interdisciplinary group that pairs the physicochemical
analyses of model ENMs with direct evaluations of toxicity using model cells
and cell cultures in order to better understand mechanisms of toxicity. In
this report, we will discuss recent data on the toxicity of a model ENM,
HfO2, using traditional and novel approaches to measure cytotoxicity.
Additionally, we will discuss the importance of ENM “contaminants” in
producing cytotoxicity, and how this may impact production and cleanup
during ENM manufacturing. (PDF)
(Movie 1) (Movie
2) (Movie 3) |
| Oct. 1 |
Host: Russell
Mumper, Russell Mumper,
Director, Center for
Nanotechnology in Drug Delivery, Division of Molecular Pharmaceutics,
University of North
Carolina-Chapel Hill
Presentation by: Shalini Minocha, Center for
Nanotechnology in Drug Delivery, Division of Molecular Pharmaceutics, UNC
Eshelman School of Pharmacy, UNC-Chapel Hill
Topic title: "Characterization and Systematic Evaluation
of the Toxicity of Metal-based Nanoparticles"
Abstract: Manufactured Nanoparticles
(MNPs) are being commonly used in
semiconductors, microelectronic devices, cosmetics and drug carriers due to
their enabling physical/chemical properties including small size. These
properties also increase the probability of the interaction of MNPs with
proteins, cells, and sub-cellular structures. The evaluation of the
toxicity of MNPs has attracted much attention in recent years. The
challenges associated with determining toxicity of nanoparticles are
multifold as factors such as size, zeta potential, surface area,
composition, hydrophobicity and impurities that may contribute to toxicity.
Therefore, it is extremely important to test a set of MNPs that allows
conducting systematic toxicity evaluation of the unique properties of MNPs
and their contribution to toxic end points/mechanisms. Our talk will start
with the characterization and in-vitro toxicity evaluation of MNPs of
different compositions including aluminum oxide, titanium dioxide and carbon
NPs. The talk will also include initial studies on the toxicity of a matched
set of carbon-coated and bare copper and nickel NPs in human alveolar
epithelial (A549) cells. (PDF) |
| Oct. 15 |
Host: Yoshio
Nishi, Professor of Electrical Engineering and Director, Stanford Nano
Fabrication Facility, Stanford University
Presentation by:
Masaharu Kobayashi, Department of Electrical Engineering, Stanford University
Topic title: Radical Oxidation of Germanium for Interface Gate
Dielectric GeO2 Formation in Metal-Insulator-Semiconductor Gate Stack
Abstract: Ge channel as a possible candidate for high
performance MOSFET has been now widely studied with an intense focus of how
to improve the Ge-insulator interface characteristics. This talk will
cover our efforts of radical oxidation of germanium surface for better
controlled interface structures and electronic properties, and discuss
future potential of this technology and applications. (PDF) |
| Oct. 29 |
Host: Farhang
Shadman, Chemical & Environmental Engineering, University of Arizona
Presentation by: Michael J. Arnold, Director, Engineering
Management Program, Systems and Industrial Engineering, University of Arizona
Topic title: A New Framework for Understanding the
Economics of Semiconductor Research Discovery
Abstract: Students conducting research in topical areas
of importance to the semiconductor industry often times lack an appreciation
of the economic driving forces that determine whether or not their
discoveries have commercial viability. The pressure on academia to reduce
credit hours has resulted in subject areas such as economics being
eliminated from many undergraduate engineering curriculums. In an effort
to educate graduate engineering and science students to better understand
the value of research discovery, new coursework has been developed assuming
little or no prior background in engineering economics.
The course titled “Financial Modeling for Innovation”
is offered to engineering students who have a desire to understand the value
proposition of technological discovery. This course is designed to promote
the understanding of business concepts in the terminology of engineering and
the quantitative structure of the course appeals to engineering students.
Students create a financial model of a venture and test basic assumptions on
growth, costs, etc. with respect to their impacts on venture value.
Financial modeling of a venture accelerates the understanding of business
planning and is the basis for determining value. Understanding valuation
leads into the subject of investment and subsequent ownership.
The expected outcome is that engineers and scientists
engaged in research recognize very early those discoveries that are likely
to have commercial promise and have the knowledge and tools to quantify
value. (PDF) |
| Nov. 12
(Daylight svg starts Nov 1st) |
Host: Inga Musselman,
Associate Provost, Office of the Executive Vice
President and Provost; Professor, Department of Chemistry, The University of
Texas at Dallas
Presentation by: Chi-cheng Chiu, Graduate
Student, Department of Chemistry, The University of Texas at Dallas
Topic title: Computer Simulations of the Interaction
between Carbon Based Nanoparticles and Biological Systems
Abstract: The interaction of carbon based
nanoparticles (CNPs) with biological systems and the environment has drawn
increased attention due to their enormous potential applications in the
nanoelectronics industry. Molecular simulations have been widely used to
reveal molecular insights and predict the chemical, physical, and biological
properties of various systems. The driving force behind the need for
molecular simulation in nanoscience is the fact that there are few
experimental techniques capable of directly imaging or probing nanoscale
systems. Much of this information is currently accessible only by simulation
(e.g. the structure and dynamics at or near a nanosurface, transport across
nanointerfaces, bonding and reactivity at nanosurfaces). Molecular
simulation can effectively complement experimental efforts by providing
insight into mechanisms and providing a framework in which to interpret
experiments. Here we used coarse-grain molecular dynamics (CGMD)
simulations to study C60 and carbon nanotubes (CNTs) interacting with a
biological membrane.
We first derive CG force field parameters for C60 and carbon nanotubes by
using optimized benzene CG parameters. Solubility, transfer free energy, and
dimerization free energy data for C60 and CNTs obtained using the proposed
models show excellent agreement with experimental and fully atomistic MD
data. Using the developed CG model, we found C60 molecules tend to form
clusters in a lipid bilayer. The aggregation behavior of the present CG
force field differs considerably from that of models currently in widespread
use. The model was further applied to study the interaction between the CNTs
and a biological membrane. Effects of degree of carboxylation, CNT diameter,
and multi-walled versus single-walled CNTs were examined. The combined
results provide a strong basis for future large scale MD studies involving
CNPs and biological systems. (PDF) |
| Nov.
26 |
No
TeleSeminar - THANKSGIVING HOLIDAY |
| Dec. 10 |
Host: Yun
Zhuang & Ara
Philipossian, Chemical & Environmental Engineering, University of Arizona
Presentation by: Dr. Yun Zhuang, Chemical &
Environmental Engineering, University of Arizona
Topic title:
"Effect of
Pad Micro-Texture on Frictional Force, Removal Rate, and Wafer Topography
during ILD/STI CMP Processes"
Abstract: Chemical mechanical planarization (CMP) is widely
used in the semiconductor industry for planarizing over-deposited material
layers. During CMP processes, material removal is
based on the synergestic work of two mechanisms: chemical and mechanical.
The chemical mechanism is supplied by an aqueous solution or slurry that
chemically reacts with the wafer surface; while the mechanical contribution
results from the relative motion and pressure exerted between the pad and
the wafer when the wafer is pressed down and rotates against the pad during
polishing. In this study, the effect of pad micro-texture on
frictional force, removal rate, and wafer topography during ILD/STI CMP
processes was investigated. Blanket 200-mm TEOS wafers and SKW3-2 patterned
STI wafers were polished and frictional force was measured in real-time
during polishing. Two diamond discs (3M A2810 diamond disc and Mitsubishi
Materials Corporation (MMC) diamond disc with triple ring dot (TRD) design)
were used to condition an IC1000 K-groove pad with Suba IV sub-pad during
wafer polishing. For each diamond disc, two conditioning forces (6 and 10
lb) were used. Under each conditioning force, five blanket TEOS wafers and
three SKW3-2 STI wafers were polished at 4 PSI and 1.2 m/s to confirm the
experimental reproducibility. A pad sample was taken after blanket TEOS
wafer polishing, as well as after patterned STI wafer polishing. Pad contact
area and surface topography were analyzed using a Zeiss LSM 510 Meta NLO
laser confocal microscope. Pad contact area, pad surface height probability
density function and abruptness, and pad summit curvature were established.
When the conditioning force increased from 6 to 10 lb, the coefficient of
friction (COF) increased by 5% and 7% for the 3M A2810 disc and MMC TRD
disc, respectively. In comparison, the removal rate increased by 43% and
65%, and the pad contact area decreased by 32% and 73% for the 3M A2810 disc
and MMC TRD disc, respectively. This indicated significantly smaller contact
area and larger contact pressure were formed under the conditioning force of
10 lb, resulting in significantly higher removal rates for both diamond
discs. The contact area during patterned wafer polishing was larger than
that during blanket wafer polishing for both diamond discs at 6 and 10 lb
conditioning forces. In addition, the pad surface was less abrupt and the
mean summit curvature was smaller during patterned wafer polishing than that
during blanket wafer polishing for both diamond discs at 6 and 10 lb
conditioning forces. Dishing and erosion analyses were performed on
100-micron pitches on the wafer center with different pattern densities. The
MMC TRD disc generated higher dishing and erosion than the 3M A2810 disc
under both 6 and 10 lb conditioning forces. The mean summit curvature of the
MMC TRD disc was larger than that of the 3M A2810 disc at both 6 and 10 lb
conditioning forces during patterned wafer polishing, indicating sharper pad
summits contributed to higher dishing and erosion for the MMC TRD disc.
(PDF) |
| Dec.
24 |
No TeleSeminar
- CHRISTMAS HOLIDAY |
|
