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Clarkson University Receives $ 30 Million from Wallace H. Coulter Foundation continued Wallace H. Coulter (1913-1998) is noted as one of the most accomplished inventors of the twentieth century, recognized for advances in hematology and cell analysis that revolutionized laboratory medicine. In the late 1940s, Coulter established a basement laboratory and conducted experiments in electronics and cell biology, seeking ways to improve clinical testing. The result of this experimentation was the invention of the Coulter Principle in 1948, for which he received a patent in 1953. The Coulter Principle was a dramatic breakthrough that provided a methodology for counting, measuring, and evaluating microscopic particles suspended in fluid. This was closely followed by his development of the "Coulter Counter," which is used to perform the most common medical diagnostic test, the complete blood count, or CBC. |
Calendar of Events
CAMP's Seventh International Symposium on Chemical-Mechanical Polishing
(CMP)
A Symposium in Honor of Professor Egon Matijevic' CAMP
Fall Meeting (For information about CAMP industrial short courses, please call Professor Richard Partch at 315-268-2351 or send email to him at partch@clarkson.edu).
** Information, on these and other CAMP events, is
available at the CAMP web site at http://www.clarkson.edu/camp |
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Graduate student Rajesh Appat is working with Professor Subramanian on predicting the polishing rates of steps on patterned wafers. The initial modeling work is focused on fixed abrasive pads used for polishing oxide films in applications such as shallow trench isolation (STI). In fixed abrasive pads, an abrasive such as ceria is incorporated into pillars on a flat polymer substrate, and is held together by a binder. The binder disintegrates during polishing, exposing the abrasive particles. Two important reported features of fixed abrasive polishing of STI oxide films are that the rate at which a step is polished is a stronger function of pattern density than is the case when a slurry containing abrasive particles is used, and that the polish rate of blanket films is extremely low. A preliminary model was developed that captures these two features. An article that describes the model and provides sample predictions was published in Electrochemical and Solid State Letters (2001). In this model, it is assumed that the removal of material from a step during its traverse is limited by the available supply of alkali in the neighboring recesses, and that this alkali diffuses rapidly to the top of the step where, in conjunction with the abrasive action, it helps to remove material. Appat has been developing a more detailed model in which the alkali transport in the recess is described by a suitable convective diffusion equation, which is solved along with the associated initial and boundary conditions.
In addition, Professor Subramanian is working with doctoral student Qingjun Qin on developing theoretical descriptions of various aspects of polishing in an orbital polishing tool. A SpeedFam/IPEC 676 orbital tool is available at Clarkson for testing predictions from these modeling efforts. Experiments have been performed on the polishing of blanket copper films deposited on 200 mm silicon wafers, using an abrasive-free chemical solution for material removal. In these experiments, the concentration of the chemical and the orbital speed were both varied, and the variation of material removal rate was measured as a function of radial position on the wafer in each case. One of the objectives of the model is to predict these radial variations of removal rate. The pad is constructed with a rectangular grid of grooves, and the slurry is introduced from underneath the pad through a set of 61 holes that are located at the intersections of selected grooves. The model involves describing the flow behavior in the groove structure of the pad, and combining this description with a model of the relative motion of each point on the wafer relative to the pad.
For more information about Professor Shankar Subramanian and his research, you may call him at
315-268-6648 or send email to
subramanian @ clarkson.edu.
______________________________________
CAMP Professor Ahmadi Models Particle Transport, Deposition, and Removal
Clarkson Distinguished Professor Goodarz Ahmadi, of CAMP and Clarkson University's Department of Mechanical and Aeronautical Engineering, models particle transport, deposition, and removal in a variety of diverse research projects. His studies include the modeling of three-phase slurry reactors, the fundamentals of natural gas and species flows from hydrates dissociation, the chemical-mechanical polishing process, the transportation and deposition of atmospheric particles near a building, inhalation drug delivery& lung deposition and computer modeling of ash particle transport to boiler surfaces. Highlights of his work are provided.
Professor Ahmadi is collaborating with scientists at the Department of Energy in modeling a three-phase slurry reactor for synthetic liquid fuel production from coal. One main objective is to develop an advanced computational capability for predicting the transport and processing of three-phase (liquid-gas-solid) slurry reactors. The specific objective is to develop an accurate and reliable computational model for predicting the process parameters using the extended thermodynamically consistent anisotropic theories of multiphase flows.
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