Defect reactions and impurity control in silicon

This Ph.D. thesis has covered the scientific issues of defect reactions involving dopants and impurities in Si, and the applications of this knowledge to reactive ion etching (RIE) and Fe gettering processes. The reactions among self-interstitials (Sii), vacancies (V), impurities (C, 0), and dopants (B, P) in Si produce undesirable defects which affect device operation and control transport processes such as dopant diffusion. Electron beam irradiation has been used to generate Sii and V to initiate the defect reactions. Deep level transient spectroscopy (DLTS) has been used to identify specific defects and to measure defect concentrations. The experimental results can be summarized in terms of a complex hierarchy diagram of defect reactions. We describe the defect reactions as a three-step process: (i) the displacement reaction to generate Sii and V, (ii) the Watkins replacement reaction to generate C and B interstitials (Ci, Bi), and (iii) the diffusion limited pairing and clustering processes to generate defect pairs and clusters. On the basis of reaction kinetics, we have simulated the reaction processes. The interstitial migration enthalpy (Him) and capture radius (r,) are two parameters used in the model to describe the long range migration and the near neighbor capture of mobile interstitials. The calculated defect reaction rates are in good agreement with the experimental data. We conclude that the diffusion limited pairing reactions are the predominant processes in the defect reactions. The reaction kinetics are determined by Him, r,, and the background dopant and impurity concentrations. The model supports the defect assignments by DLTS. The model can be improved by including pair breakup processes and large interstitial clusters.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Nuclear Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

1997

Author dc:creator

• Zhao, Song, 1964-

Advisor dc:contributor.advisor

• Lionel C. Kimerling.

• Nuclear 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/1721.1/8635

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8635