Phase field model for precipitates in crystals

Oxygen precipitate caused by oxygen supersaturation is the most common and important defects in Czochralski (CZ) silicon. The presence of oxygen precipitate in silicon wafer has both harmful and beneficial effects on the microelectronic device production. Oxygen precipitates are useful for gathering metallic contaminants away from the device regions and for increasing the mechanical strength of the wafer [Borghesi, 1995], but they also can destroy the electrical and mechanical characteristics of the semiconductor and microelectronic devices [Abe, 1985; Kolbesen, 1985]. The understanding of the mechanism of the formation and growth of the oxygen precipitates in CZ silicon is a key to improve the quality of silicon wafer. The goal of this thesis is to provide a full understanding of the growth of an isolated oxygen precipitate in CZ silicon and its morphological evolution by means of phase-field method, and to gain the insight of the morphological transition of the oxygen precipitate and the distribution of oxygen, vacancy, and self-interstitial around the single oxygen precipitate. The traditional approach to simulate multiphase system is the sharp interface model. Sharp interface model requires tracking the interface between phases, which make the simulation much difficult and complicate. Phase-field model offers an alternative approach for predicting mesoscale morphological and microstructure evolution of inhomogeneous multiphase system. The most significant computational advantage of a phase-field model is that explicit tracking of the interface is unnecessary. In this thesis, the phase-field model is applied to simulate the evolution of oxygen precipitates in CZ silicon. A phase-field model for a two-component inhomogeneous system was first derived to set up the framework of phase-field method and a dynamically adaptive finite element method also was built to specifically solve phase-field equations. This model was used to investigate the effects of interfacial and elastic properties on the growth of a single precipitate, coarsening of two precipitates, and competitive growth of multiple precipitates. For an isolated precipitate growth, both elastic energy and interfacial energy affect the precipitate morphological evolution.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• She, Minggang

Advisor dc:contributor.advisor

• Robert A. Brown.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/46020

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/46020