Controlling iron and copper precipitation in silicon wafers

Savin, Hele

Controlling iron and copper precipitation in silicon wafers

dc.contributor	Aalto-yliopisto	fi
dc.contributor	Aalto University	en
dc.contributor.author	Savin, Hele
dc.contributor.department	Department of Electrical and Communications Engineering	en
dc.contributor.department	Sähkö- ja tietoliikennetekniikan osasto	fi
dc.contributor.lab	Electron Physics Laboratory	en
dc.contributor.lab	Elektronifysiikan laboratorio	fi
dc.date.accessioned	2012-02-17T07:15:19Z
dc.date.available	2012-02-17T07:15:19Z
dc.date.issued	2005-10-21
dc.description.abstract	This thesis studies the two most common transition metals in silicon – copper and iron. The purpose of the experiments and theoretical calculations presented in this thesis is to increase the current knowledge of the precipitation behavior of these metals under different processing conditions. The study also includes the development of recombination lifetime methods for impurity characterization in silicon. A method to measure trace copper contamination in silicon using the microwave photoconductivity decay is proposed. The method is based on the observation that copper precipitates can be created using light activation. It is shown that external charge on wafer surfaces can reduce the copper out-diffusion, which extends the applicability of the method. Moreover, oxide precipitates are found to increase the sensitivity of the method. An analytical solution to the current continuity equation for excess carriers in an epitaxial structure under time dependent optical excitation is derived. In addition, some analytical approximations are developed and numerical calculations are made to check their accuracy. The built-in potential between the epitaxial layer and the substrate is taken into account and also the light induced barrier lowering is included in the model. The barrier lowering is found to be noticeable and can affect the effective lifetime by up to two orders of magnitude. Several annealing profiles and contamination levels are used to study the iron gettering behavior at varying supersaturation levels. It was found that the gettering efficiency depends strongly on the initial iron concentration and considerably high supersaturation is needed to initiate the gettering. The results are discussed from the perspective of thermodynamics. The thermal stability of internally gettered iron is studied experimentally by deep level transient spectroscopy. The experiments reveal that the dissolution is a reaction limited process. The simulations of iron re-dissolution show that instead of simulating only the final cooling, it is important to simulate the whole thermal cycle. This is important since low thermal budgets are becoming more and more common in the IC technology.	en
dc.description.version	reviewed	en
dc.format.extent	43, [32]
dc.format.mimetype	application/pdf
dc.identifier.isbn	951-22-7873-1
dc.identifier.issn	1795-4584
dc.identifier.uri	https://aaltodoc.aalto.fi/handle/123456789/2614
dc.identifier.urn	urn:nbn:fi:tkk-005749
dc.language.iso	en	en
dc.publisher	Helsinki University of Technology	en
dc.publisher	Teknillinen korkeakoulu	fi
dc.relation.haspart	H. Väinölä, M. Yli-Koski, A. Haarahiltunen, and J. Sinkkonen, Sensitive copper detection in p-type CZ-silicon using μPCD, Journal of The Electrochemical Society, Vol. 150, G790-G794 (2003). [article1.pdf] © 2003 The Electrochemical Society. By permission.
dc.relation.haspart	H. Väinölä, E. Saarnilehto, M. Yli-Koski, A. Haarahiltunen, J. Sinkkonen, G. Berenyi, and T. Pavelka, Quantitative copper measurement in oxidized p-type silicon wafers using microwave photoconductivity decay, Applied Physics Letters, Vol. 87, 032109 (2005). [article2.pdf] © 2005 American Institute of Physics. By permission.
dc.relation.haspart	H. Väinölä, J. Storgårds, M. Yli-Koski, and J. Sinkkonen, Evaluation of effective carrier lifetime in epitaxial silicon layers, Solid State Phenomena, Vols. 82-84, 771-776 (2002).
dc.relation.haspart	H. Väinölä, J. Storgårds, M. Yli-Koski, and J. Sinkkonen, Light induced change on the built-in potential of p/p+ structures and its effect on carrier lifetime measurements, Materials Science and Engineering B, Vols. 91-92, 421-424 (2002).
dc.relation.haspart	H. Väinölä, A. Haarahiltunen, E. Saarnilehto, M. Yli-Koski, J. Sinkkonen, and O. Anttila, Enhancement of internal gettering efficiency of iron by low temperature nucleation, The Electrochemical Society Proceedings, Vol. 05, High Purity Silicon VIII, Editors: C. L. Claeys, M. Watanabe, R. Falster, P. Stallhofer, p. 160-164 (2004). [article5.pdf] © 2004 The Electrochemical Society. By permission.
dc.relation.haspart	P. Zhang, H. Väinölä, A. Istratov, and E. R. Weber, Thermal stability of internal gettering of iron in silicon and its impact on optimization of gettering, Applied Physics Letters, Vol. 83, 4324-4326 (2003). [article6.pdf] © 2003 American Institute of Physics. By permission.
dc.relation.haspart	H. Väinölä, P. Zhang, A. Haarahiltunen, A. Istratov, and E. R. Weber, Simulations of iron re-dissolution from oxygen precipitates in CZ-silicon and its impact on gettering efficiency, Solid State Phenomena, Vols. 95-96, 581-586 (2004).
dc.relation.ispartofseries	TKK dissertations	en
dc.relation.ispartofseries	12	en
dc.subject.keyword	photoconductivity decay	en
dc.subject.keyword	recombination lifetime	en
dc.subject.keyword	epitaxial	en
dc.subject.keyword	internal gettering	en
dc.subject.keyword	oxide precipitates	en
dc.subject.other	Electrical engineering	en
dc.title	Controlling iron and copper precipitation in silicon wafers	en
dc.type	G5 Artikkeliväitöskirja	fi
dc.type.dcmitype	text	en
dc.type.ontasot	Väitöskirja (artikkeli)	fi
dc.type.ontasot	Doctoral dissertation (article-based)	en
local.aalto.digiauth	ask
local.aalto.digifolder	Aalto_68429