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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- 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"
  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”
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 byGreg 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
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 bySarah 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 byJin-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)
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"
:  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

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