ABSTRACTS



The following is a list of the abstracts for papers which will be presented in ELEVENTH INTERNATIONAL SYMPOSIUM ON PARTICLES ON SURFACES: DETECTION, ADHESION AND REMOVAL. The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Firefox. Netscape, ... etc.)


Uwe Schlosser, Thomas Bahners and Eckhard Schollmeyer; Deutsches Textilforschungszentrum Nord-West e. V., Adlerstr. 1, 47798 Krefeld, GERMANY

Email: info@dtnw.de



Some Remarks on the Removal of Adhering Particles by Oscillating Air Flows



On the background of technical concepts for the removal of particles from moving textiles by air flows, e.g. after weaving or before coating, some theoretical remarks on hydro-dynamical forces acting on particles are given. As the main removing forces, drag and buoyancy are taken into consideration and related to the acting adhesion forces.

A focus is set on the application of oscillating air flows - in contrast to uni-directional flows - which can be produced by means of pneumatic generators at ultrasonic frequencies.


Thomas Bahners and Eckhard Schollmeyer; Deutsches Textilforschungszentrum Nord-West e. V., Adlerstr. 1, 47798 Krefeld, GERMANY

Email: info@dtnw.de



Electrospun Nanofibers - a Way to Improved Wet Filtration Efficiency of Deep-bed Filters



Electrospinning - more precisely: electrostatic fiber formation - is an interesting technology to produce very fine fibers with sub-micrometer diameter. In the process, a strong inhomogeneous electric field acts on a polymer solution leading to the extraction of a polymer jet which solidifies and orientates through the evaporation of the solvent. At least in theory fibers may be spun from any soluble polymer, including biopolymers. Irregular webs made of these fibers have the potential form highly efficient filters for micron and submicron particles but also bacteria or viruses.

The scope of the presented work was to study the separation of micron and sub-micron model particles from fluid systems by a deep-bed filter concept consisting of a multilayer stack of combined nanofiber/non-woven layers. Polystyrene (PS) spheres suspended in water served as the model system. In the concept, the nanofibers were meant to form an irregular small pore system with high porosity and high flow properties at the same time. Nanofibers of an average diameter of 125 15 nm were produced from polycaprolactone (PCL) by electro-spinning, a commercial non-woven serving as the base of the individual layers. The model filters were characterized with regard to separation efficiency, flow rate and separation morphology.


E. Kesters1, M. Claes1, Q.T. Le1, K. Barthomeuf 2, M. Lux1, G. Vereecke1*, T. Bearda1 and J. B. Durkee3



1) IMEC, 75 Kapeldreef, 3001 Leuven, Belgium

2) INSA, Lyon, France

3) Precisioncleaning, PO Box 847, Hunt TX 78024, USA

* guy.vereecke@imec.be



Selection of ESH Solvents for Cleaning Applications in Semiconductor Manufacturing



In semiconductor manufacturing photoresist layers are used to protect some areas of silicon wafers from plasma etch chemistries and ion implantation. After completion of the process, the photoresist (PR) needs to be selectively removed and the surface cleaned, ensuring a residue and particle free surface. While strong oxidizing aqueous or plasma chemistries can remove processed PR layers, they are encountering compatibility issues with new materials introduced to increase the performance of new chips generations. Consequently, all-wet processes based on organic solvents are gaining renewed interest for the removal of processed PR layers. However changes in regulations call for a reduction in the ESH impact of solvents used in manufacturing. In this respect, n-methyl-pyrrolidone (NMP), an efficient solvent used in strippers, is going to be re-classified as a reprotoxin (Cat. 2) and needs to be replaced.

In this work, solvents were selected in compliance with a set of ESH criteria and evaluated as to their efficiency in wetting and dissolving two DUV (193 nm) PR. Tests were performed on pristine PR layers taken as model for the least modified fraction of processed PR layers. The use of Hansen approach in solvent selection was also evaluated by testing mixtures of ESH solvents with solubility parameters matching those of known good solvents (such as NMP).

Used ESH selection criteria were based on EEC classifications and are summarized in Table 1. Although mixtures may provide better solubility properties compared to pure components, replacement of good non-ESH solvents by mixtures of ESH solvents on basis of matching solubility parameters did generally not work. Selection process and reasons for disagreement with Hansen theory will be discussed in more details.

Table 1. ESH criteria used in solvent selection
Risk category Criteria1
Environment No toxicity to aquatic & non-aquatic environment (no R50-R59 solvents, no N label)
Safety Flash point FP > 55 C (no F+, F, and R10 solvents)
Health
  • No very toxic (T+) and toxic (T) solvents (no R23-28, R39, R48 solvents)


  • No carcino/mutagenic & reprotoxic solvents (of all cat.; T, Xn) (no R40, R45-46, R49, R60-63, R68 solvents)



John B. Durkee and Anselm Kuhn; POB 847 Hunt, TX 78024



Measuring Particulate Surface Contamination in an Industrial Setting



Particulate surface contamination is increasingly recognized as harmful, whether in straightforward engineering assemblies or in subsequent application of any form of coating. Use of more sophisticated instrumental techniques such as SEM or Auger Electron Spectroscopy is not an option in many industrial settings. A survey of the more accessible techniques is presented, against a background of the various national and international standards which are relevant here.

Three main avenues of attack are discussed in turn. Contaminant particles can be viewed, quantified and characterized in situ on the surface. Viewing and illumination may be normal or, for micron-sized particles, be based on light-scattering. Particles can be removed with a liquid, being then characterized and estimated in suspension in that liquid by optical transmission. Lastly, after removal from the surface, usually by a liquid, they can be extracted onto a filter surface, prior to quantification and characterization there.

For measurements in the field, the ready availability of digital cameras and WiFi has transformed what was hitherto a laborious and time-consuming process.


Chuck Extrand; Entegris Research Group, Entegris, Inc., 3500 Lyman Blvd., Chaska, MN 55318



Super Wetting of Structure Surfaces



(Abstract not yet available)


David Grojo1 and Philippe Delaporte2



1) National Research Council, Steacie Institute for Molecular Sciences, 100 Sussex Drive, Ottawa, ON K1A 0R6, CANADA



2) LP3, UMR 6182 CNRS - Université Aix-Marseille II, Case 917, F-13288 Marseille Cedex 9, FRANCE



Laser-particle Processing: from Decontamination to Nanofabrication



Due to downscaling, the emerging nanotechnology industry requires new cleaning tools providing the ability to remove nanometer-size defects. The dry laser cleaning technique, which simply consists of the irradiation of materials with nanosecond laser pulses, is considered as a promising approach. Our study contributes to a better understanding of the "laser-particles-surfaces" interaction processes. The experiments show that the removal results from a competition between several mechanisms. The ablation of molecular water trapped at the vicinity of contaminates was identified as the dominant cleaning mechanism in the low fluence regime. Among the optical damage mechanisms observed with larger fluences, we analyzed the substrate nanopatterning induced by near-field enhancement underneath the particles. Although this mechanism is not compatible with damage-free cleaning requirements, it has potential applications, like the fabrication of nanodevices.


Sandip Halder, Twan Bearda, Karine Kenis, Tom Janssens, Toan-Le Quoc, Kurt Wostyn, Peter Leunissen, and Paul Mertens; IMEC, Kapeldreef 75, B-3001 Leuven BELGIUM

Email: halder@imec.be



Kyung-Hyun Kim, Samsung Affiliate at IMEC



Michael Andreas, Micron Affiliate at IMEC



Particle Removal Efficiency and Damage Analysis of Patterned Wafers in Different Solvents after Megasonic Cleaning

The constant drive towards increased integration of transistors with different threshold voltages on a single chip has led to an ever-increasing number of masks. This in turn leads to an increase in the number of cleaning steps. The surface preparation roadmap specifies the maximum allowable loss of oxide and silicon during each cleaning step to be 0.4 A [1]. Hence chemical cleans involving etching of the substrate is being replaced by physical cleaning. Among the physical cleaning methods megasonic as well as spray cleaning methods are becoming more and more preferable.


Hubert Gojewski 1,2, Arkadiusz Ptak2 and Michael Kappl 1



1) Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, GERMANY

2) Institute of Physics, Faculty of Technical Physics, Pozna University of Technology, Nieszawska 13A, 60-965 Pozna, POLAND

Adhesion on Self-assembled Thiol Monolayers by Means of High-rate Dynamic Force Spectroscopy

Adhesion forces can accurately be measured by means of atomic force microscopy (AFM) in the so-called force spectroscopy mode where forces are measured as a function of separation between AFM tip and sample [1]. For many materials like polymers, proteins or thiols the adhesion interactions is a function of separation or unloading rate [N/s]. Using AFM force spectroscopy using different unloading rates - also known as dynamic force spectroscopy - allows in principle to study such adhesion phenomena. However, with commercial AFMs, the range of unloading rates is quite limited. For this study we modified a commercial AFM to enlarge the standard range of loading rates by up to 4 orders of magnitude [2]. This modification allows us to obtain not only static information as gained in standard AFM adhesion force measurements, but also dynamics of the rupture process is probed. As model samples, different self-assembled monolayer of thiols on gold (111) coated mica are prepared and measured using DFS at ambient condition and different values of humidity. Varying contact times down to the millisecond range allows us to get information about the kinetics of meniscus formation responsible capillary forces.



[1] H.-J. Butt, B. Capella, M. Kappl, Surf. Sci. Rep. 59 (2005) 1

[2] A. Ptak, M. Kappl, H.-J. Butt, Appl. Phys. Lett. 88 (2006) 263109


Rajiv Kohli; Washington Group International, NASA Johnson Space Center, P.O. Box 58128, Houston, TX 77258



Removal of Micro and Nanosize Contaminant Particles from Solid Surfaces



(Abstract not yet available)


G. Lefèvre1, M. Fédoroff1, G. Cote1, O. Dégardin1,2, Lj. erovi1, S. Delaunay3, E.-M. Pavageau3, C. Mansour3, H. Catalette3, A. Jaubertie2, A. Douce2



1) ENSCP - LECA - CNRS UMR 757511, Rue Pierre et Marie Curie, F-75231 Paris Cedex 05 FRANCE

2) EDF R&D / MFEE6, Quai Watier - BP 49, F-78400 Chatou FRANCE

3) EDF R&D / MMC / T29, Avenue des Renardières - Ecuelles,

F- 77818Moret-sur-Loing Cedex FRANCE



Studies on the Deposition of Metallic Oxides Particles - Application to Cooling Circuits of Pressurized Water Reactors



Deposition of particles in industrial equipments where a fluid is circulating is the cause of several technical problems. This process leads to the fouling of heat exchangers and the radioactive contamination of cooling circuit of nuclear reactors. A common project between an academic laboratory and an industrial research center was built to understand and predict the behaviour of particles in cooling circuits of Pressurized Water Reactors (PWR). Several experimental set-ups have been developed to study the deposition of metallic oxides particles (magnetite and hematite) in a wide range of physico-chemical and hydrodynamical conditions, from laboratory scale to pilot experiments. In turbulent flow, the kinetics of deposition and the structure of the deposited layer were measured as a function of solution composition (pH, amines, boric acid,), temperature (25 - 300C) and thermohydraulics (in presence of a heat gradient or in isothermal condition). The analysis of the suspension and the deposited layer was perfomed by in-situ real-time methods based on optical techniques (turbidimetry, UV-Vis reflectometry,) or after sampling (SEM, elemental analysis,).


M. K. Mazumder; Department of Applied Science, ETAS 575, College of System Engineering and Information Science, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204



Dust Hazard Mitigation Methods for Mars and Lunar Missions



(Abstract not available)


Isabelle Tovena Pecault 1, GUILLAUME BASSO 2, François Gensdarmes2



1) CEA/DAM CESTA, DLP/SCAL/LPO, BP 2, 33114 Le Barp, FRANCE

isabelle.tovena-pecault@cea.fr



2) Institute for Radioprotection and Nuclear Safety (IRSN), Aerosol Physics and Metrology Laboratory BP 68, 91192 Gif sur Yvette cedex, FRANCE



Qualification of Particle Surface Probes: Requirements and Development of a Test Bench



For high-tech industries, such as semiconductor or optical ones, controls must be done not only on airborne particle contaminants in clean rooms but also on surface particle contamination. Nowadays, an international standard is on progress: ISO 14644-9. This standard "Clean rooms and associated controlled environments Part 9: Classification of surface particle cleanliness" describes the classification of the particle contamination levels on solid surfaces in clean rooms. Recommendations on testing and measuring methods as well as information about surface characteristics are given in informative annexes. This standard applies to all solid surfaces such as walls, ceilings, floors, working environment, tools, equipment and devices. The surface particle cleanliness classification is limited to particles between 0.05 m and 500 m.

In order to classify the particle contamination on metallic or plastic or glass surfaces, surfacic commercial probes exists but none of them are correctly calibrated. In this paper, a qualification bench developed in collaboration between CEA and IRSN is described and the results obtained for a surfacic probe based on airflow particle resuspension and optical particle counter measurement are presented. The effects of particle-surface nature and particle diameter are discussed on the bases of resuspension efficiency and transmission-detection efficiency for particles between 30 m and 80 m.


Luigi Scaccabarozzi; ASML, De Run 6501, 5504 DR Veldhoven, THE NETHERLANDS



Specifications and Prospects for Cleaning and Inspection of EUV Reticles



Due to large absorption of EUV light, EUV reticles are not expected to have pelleciles for particulate contamination protection. The lack of a pellicle means that having a means of cleaning and inspecting pellicles that could be adapted to insitu use is of great interest. Even nanosize particles could result in fatal defects in every die of the wafer. Consequently, measures must be taken to detect and remove any particle above a certain critical size, accidentally deposited on the reticle.

In this talk we will present the issues and challenges we are facing in the detection and removal of particles from EUV reticles. Very stringent specifications are required to ensure that practically no particle is present at the time of exposure. We will then give an overview of the technologies that ASML is investigating in order to meet these specifications. These include laser scatterometry techniques for the inspection part and different dry cleaning techniques. For the former, the challenge is the detection of sub 50nm particles on patterned reticles within minutes, while for the latter, the main challenge is to remove any type of particle (organic/inorganic) in the same timescale and without damaging the pattern. Results, including cleaning of 50-nm PSL spheres using dry techniques, will be discussed.


F. Wali 1, D. M. Knotter 2, J.J. Kelly 3, F. Michel 2, and M van Straten 2



1) University of Twente,

2) NXP semiconductors, Gerstweg 2 (FB 0.049D), 6534 AE Nijmegen, THE NETHERLANDS

3) University of Utrecht



E-mail: faisal.wali@NXP.com



Preparation of mono-disperse silica particles with metal-ion tracer



In semiconductor technology, removal of nanoparticle contamination from the surface of the substrate is an essential requirement. For an effective particle removal study, proper detection of the particles is important. The conventional method to detect the particles is based on the light scattering principle; this cannot distinguish between the signals of nanoparticles and background noise. This limitation has hampered further investigation of removal of nano-sized particle contamination. To circumvent this problem, we propose to use particles with metal-ion tracer that can be detected with ICP-MS. In this publication, we will describe the methods to synthesize the silica particles with metal-ion core and an average size ranging from 20nm to 500nm. Particle properties such as average size, size distribution, and leaching of the metal-ions are investigated. The density of particles in the liquid as well as on the silicon surface is also verified with this new technique.


Marco L. Zoeteweij, J. C. J. van der Donck, A. M. Klinkenberg and R. Versius; TNO Science and Industry, P.O. Box 155, 2600 AD Delft, THE NETHERLANDS



Particle Removal in Linear Shear Flo: Model Prediction and Experimental Validation



A clean environment is of utmost importance in the high-end industry. terefore, decent understanding of contamination control is essential. We here present different particle removal mechanisms using a linear shear flow. the attractive Van der Waals interaction between the particle and the surface needs to be overcome by the removal forces induced by the flow. Both the attractive and removal forces depend on the particle diameter.

With a model based on the particle Reynolds number, critical particle diameters are determined for which the flow induced forces on the particles are larger than the attractive forces between the particle and the surface. for air flow at atmospheric conditions, the different particle motions, classified as lift, sliding and rotation are calculated and compared with experimental observations.

In the experimental set-up, particles with sizes between 1 and 100 micron are subjected to an air flow with linear shear rates at the wall ranging from 7x104 s-1 to 2x106 s-1. the diameters calculated for the particle lift and sliding motion are much larger than the particles that were removed experimentally. It is shown that the critical diameter for particle rotation is a good measure for the particle sizes that are removed during flow exposure. the particle diameters obtained from the experiments agree with the model predictions within several microns.



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