SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing (ERC)

                                                          **  Bringing Sustainability to Semiconductor Manufacturing **

A multi-university research center leading the way to environmentally friendly semiconductor manufacturing, sponsored by the Semiconductor Research Corporation's Global Research Collaboration (GRC) Research Program



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- 2010 -
Jan. 7, 2010 No TeleSeminar -- Holiday Schedule
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.”
AbstractSupercritical 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”
AbstractSustainable 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
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"
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"
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)"
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 “
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

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"
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"
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"
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”
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"
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"
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”
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”

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 byJeff Rottman and Hao Wang, Chemical and Environmental Engineering, University of Arizona
Topic title
"Transport of Nanoparticles in Porous Media"
"Physicochemical and Surface Characteristics Study of Nanoparticles related to ESH Impact of Emerging Nanoparticles and Byproduct in Semiconductor Manufacturing"
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"
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"
:  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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