eprintid: 168
rev_number: 4
eprint_status: archive
userid: 6
dir: disk0/00/00/01/68
datestamp: 2008-10-10
lastmod: 2015-05-29 19:48:35
status_changed: 2009-04-08 16:55:13
type: report
metadata_visibility: show
item_issues_count: 0
creators_name: Bohun, Sean C.
contributors_name: Bouhennache, Tark
contributors_name: Fairbairn, Leslie
contributors_name: Frigaard, Ian
contributors_name: Ho, Joe
contributors_name: Hodge, Alex
contributors_name: Huang, Huaxiong
contributors_name: Kamali, Mahtab
contributors_name: Kharrazi, Mehdi H. K.
contributors_name: Lee, Namyong
contributors_name: LeVeque, Randy
contributors_name: Liang, Margaret
contributors_name: Liang, Shuqing
contributors_name: Marquez-Lago, Tatiana
contributors_name: Majdanac, Allan
contributors_name: Micklethwaite, W. F.
contributors_name: Muck, Matthias
contributors_name: Myers, Tim
contributors_name: Rasekh, Ali
contributors_name: Rossmanith, James
contributors_name: Sanaie-Fard, Ali
contributors_name: Stockie, John
contributors_name: Westbrook, Rex
contributors_name: Williams, J. F.
contributors_name: Zarestky, Jill
title: Modelling InSb Czochralski Growth
ispublished: pub
subjects: materials
studygroups: ipsw5
companyname: Firebird Semiconductors
full_text_status: public
abstract: The dominant technique for producing large defect free crystals is known as the Czochralski method. Developed in 1916 by Jan Czochralski as a method of producing crystals of rare metals, this method is now used to produce most of the semiconductor wafers in the electronics industry.

Many aspects of this process have been investigated to gain a greater insight of the physical processes involved. We begin with the heat problem, first as a one dimensional model, then extending to a second dimension. This analysis indicates
that the temperature of the gas surrounding the crystal has a major impact on both the thermal stress experienced by the crystal and the shape of the crystal/melt interface. In contrast,variations in the heat 
flux from the melt have much less of an effect.

Having investigated the temperature profiles, the analysis then focuses on the behaviour of the fluid. Scaling arguments are used to estimate the thickness of the various boundary layers and explain the main flow patterns that are experimentally observed.

Next, the shape of the meniscus is determined for various rotation rates. This analysis shows that the shape of the meniscus is relatively invariant at least at low rotation rates yet the actual vertical position of the meniscus changes readily with the rate of rotation.

After analyzing the fluid flow patterns, a model is developed for the height of the melt as a function of time. This indicates that for a crystal of constant radius the proportion of the effective pull rate due to the falling fluid level remains essentially constant over the complete growing time of the crystal. This no longer remains true if the radius of the crystal is allowed to increase at a constant rate.
problem_statement: A common problem of using the Czochralski technique for producing large defect free crystals is that defects begin to appear in the crystal once the diameter of the crystal exceeds some critical value. The main objective of this study is to attempt to understand this phenomena by modelling the process mathematically. Hopefully, the model can also be used to design growth procedures that produce crystals without defects even when the diameters are greater than the critical values observed under current pull conditions. As indium antimonide (InSb) is used as an infrared detector, being able to manufacture large diameter crystals would have an immediate impact in industry.
date: 2001
date_type: published
pages: 26
citation:   Bohun, Sean C.  (2001) Modelling InSb Czochralski Growth.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/168/1/insb.pdf