Modelling Melt Motions and Mass Transport During Crystal    Growth with a Magnetic Field
{'Code': '07020000', 'Directorate': {'Abbreviation': 'ENG', 'LongName': 'Directorate For Engineering'}, 'Division': {'Abbreviation': 'CBET', 'LongName': 'Div Of Chem, Bioeng, Env, & Transp Sys'}}
{'SignBlockName': 'George P. Peterson', 'PO_EMAI': None, 'PO_PHON': None}
Single crystals of semiconductors such as silicon and gallium-                  arsenide are grown by several different processes including the                 Czochralski and float zone processes.  Wafers from these single                 crystals are used for integrated circuits, optical devices and                  many other applications.  In the liquid state, semiconductors                   behave as liquid metals and have excellent electrical                           conductivities.  Therefore, a magnetic field can be used to                     control the liquid motion during crystal growth from a melt as in               the Czochralski and float zone processes.  Without a magnetic                   field, the melt motion in a Czochralski puller is turbulent.  The               turbulence produces fluctuations in the heat transfer at the                    crystal-melt interface.  With such fluctuations, a point in the                 crystal face alternates between periods of crystallization and                  remelting, and this cycle produces a high microdefect density in                the crystal.  The progressive reduction in the dimensions of                    integrated circuit elements has led to a demand for crystals with               extremely low microdefect densities.  The application of a                      magnetic field during crystal growth eliminates turbulence and                  greatly reduces microdefect densities.  The proposed research                   deals with the effect of a magnetic field on fluid motion in the                melt during crystal growth.                                                                                                                                     It is proposed to develop models of the melt motion and transport               of dopants and impurities for the Czochralski process with a                    uniform transverse magnetic field and for the float zone process                with a uniform axial magnetic field.  For the Czochralski                       process, consideration will be given to the fluid motions for                   either a weak magnetic field or for a strong one, since these are               the only cases with a nearly axisymmetric temperature field.  For               moderate magnetic field strengths, the temperature is far from                  axisymmetric, which would produce a poor crystal.  For the float                zone process, the first objective is to determine the shape of                  the free surface and the melt motion driven by the force from the               induction coil which melts the feed rod.  Next, the other                       components of the float zone melt motion will be treated.
{'FirstName': 'John', 'LastName': 'Walker', 'PI_MID_INIT': 'S', 'PI_SUFX_NAME': None, 'PI_FULL_NAME': 'John S Walker', 'EmailAddress': 'jswalker@uiuc.edu', 'PI_PHON': '2173337979', 'NSF_ID': '000476508', 'StartDate': '09/15/1988', 'EndDate': None, 'RoleCode': 'Principal Investigator'}
{'Name': 'University of Illinois at Urbana-Champaign', 'CityName': 'URBANA', 'ZipCode': '618013620', 'PhoneNumber': '2173332187', 'StreetAddress': '506 S WRIGHT ST', 'StreetAddress2': None, 'CountryName': 'United States', 'StateName': 'Illinois', 'StateCode': 'IL', 'CONGRESSDISTRICT': '13', 'CONGRESS_DISTRICT_ORG': 'IL13', 'ORG_UEI_NUM': 'Y8CWNJRCNN91', 'ORG_LGL_BUS_NAME': 'UNIVERSITY OF ILLINOIS', 'ORG_PRNT_UEI_NUM': None}
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