Start
Dec 11, 2014 - 17:00
End
Dec 11, 2014 - 18:00
Venue
Room 118 Creativity Hall Chemical Engineering
Event Type
Speaker
Dr. Gaurab Samanta Research Scientist Quantitative Silicon Research SunEdison Semiconductor St. Peters MO.
Title
Use of Continuum Modeling to Understand Crystal Growth Systems at the Lab and the Industrial Scale
Abstract : Crystalline forms of matter are the backbones of many technologies. For example the semiconductor devices and solar cell industry requires high quality crystalline silicon (si) wafers laser and radiation detector technologies use high quality fiber crystals and nanocrystals find use in many novel applications. However in order to grow high quality crystals it is crucial to have a good understanding of the crystal growth processes. This talk concerns with how such an understanding can be developed with the aid of numerical simulations for systems where crystal is pulled from a melt pool. I will describe two processes first micro-pulling-down (μ-PD) in the lab scale and second Czochralski (Cz) in the industry scale. μ-PD process has become a method of choice to grow fiber crystals in laboratories. It is also an economically viable option when crystals of new materials are to be grown during a material discovery research. However in the absence of theoretical knowledge of proper growth conditions in the molten zone of the process time-consuming trial and error procedure is often employed. Here I discuss a quasi-steady-state (QSS) as well as time-dependent analysis using a two-dimensional axisymmetric finite element description of the molten zone of the process. QSS results show different ways in which the operation can be limited or a failure can occur. It also clearly shows the inadequacy of an old one-dimensional model developed for capillary-dominated systems in prescribing stability criteria. Time-dependent simulations are utilized to do a non-linear stability analysis of the QSS states. Conceptually the general framework utilized to conduct this investigation can be extended to other crystal-pulling-from-melt processes. Cz process is widely used in industry to make semiconductor and solar grade silicon wafers. Engineering of desired defect characteristics in the crystal is crucial for semiconductor device or solar cell fabrication. In a segment of a growing Cz crystal microdefects nucleate at different times and temperatures and grow to different sizes. Therefore a rigorous model requires very large computational expenditure to keep track of formation and path histories of various aggregates or clusters rendering it impractical for predictions. I describe a computationally efficient model based on a lumped approach to quantify the distribution of microdefect population at any given location in Cz grown silicon crystals and validated against that of a rigorous model.Bio-Sketch : Dr. Gaurab Samanta is a research scientist in Sunedison Semiconductor. He graduated with a Bachelors of Technology in Chemical Engineering from IIT Kharagpur in 2005. He obtained his doctorate of philosophy from University of Delaware in 2009. He worked under Prof. Antony Beris in the Chemical Engineering department on simulations of polymer-induced drag reducing turbulent channel flows. His thesis was on investigation of viscoelastic turbulent channel flows using proper orthogonal decomposition method. He was the Shirley and Fraser Russell Teaching Fellow at Delaware for the year 2008. He joined Prof. Jeffrey Derby’s group in University of Minnesota as a post-doctoral researcher in 2009. In Prof. Derby’s group Dr. Samanta worked on modeling of various crystal growth systems such as micro-pulling-down and convective assembly. In 2011 Dr. Gaurab Samanta joined Sunedison Semiconductor as a research scientist. His current focus of research is on industrial scale silicon crystal growth and microdefects in silicon crystal which forms the basis for semiconductor devices and commercial solar cells. Venue: Room 118 Chemical Engg.