Investigations of diffusion kinetics in Si/Ta/Cu/W and Si/Co/Ta systems by secondary neutral mass spectrometry

A. Lakatos, G. Erdelyi, G. Langer, L. Daróczi, K. Vad, A. Csík, A. Dudas, D. Beke

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Proper understanding of the degradation mechanisms and diffusion kinetics of copper and cobalt interconnections for advanced microelectronics is important from the point of view of fundamental research and technology as well. In this paper Si(substrate)/Ta(10 nm)/Cu(25 nm)/W(10 nm) and Si(substrate)/Co(150 nm)/Ta(10 nm) samples, prepared by DC magnetron sputtering, were in investigated. The samples were annealed at several temperatures ranging from 423 K to 823 K for various times. The composition distributions were detected by means of Secondary Neutral Mass Spectrometry (SNMS). Microstructural characterization of samples was carried out by means of Transmission Electron Microscopy (TEM). It is shown that the changes in the composition profiles were mainly caused by grain boundary, GB, diffusion and the effective GB diffusion coefficients of Ta in Cu were determined both by the "first appearance" and "centre-gradient" methods. The activation energy is 100 kJ/mol. The importance of the Ta penetration into the Cu and its accumulation at the Cu/W interface can lead to an increase of the Ta content in the copper film. This can be an important factor in the change/degradation of the physical parameters (e.g. the electrical resistance) of interconnects. Furthermore a Ta segregation factor in Cu was evaluated. Preliminary results in the Si(substrate)/Co(150 nm)/Ta(10 nm) indicate fast (GB) diffusion of the Si into the Co layer, formation of a cobalt silicide layer at the Co/Si interface and Si accumulation first at the Ta/Co interface and later a retarded accumulation at the free Ta surface.

Original languageEnglish
Pages (from-to)493-497
Number of pages5
JournalVacuum
Volume85
Issue number4
DOIs
Publication statusPublished - Oct 21 2010

Fingerprint

Mass spectrometry
mass spectroscopy
Kinetics
kinetics
cobalt
Cobalt
degradation
Copper
copper
Substrates
electrical resistance
microelectronics
Degradation
Acoustic impedance
Gradient methods
magnetron sputtering
penetration
diffusion coefficient
grain boundaries
direct current

Keywords

  • Centre-Gradient method
  • Co and Cu interconnection technology
  • Interface segregation
  • Si diffusion in Co
  • Ta diffusion in Cu

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Instrumentation
  • Surfaces, Coatings and Films

Cite this

Investigations of diffusion kinetics in Si/Ta/Cu/W and Si/Co/Ta systems by secondary neutral mass spectrometry. / Lakatos, A.; Erdelyi, G.; Langer, G.; Daróczi, L.; Vad, K.; Csík, A.; Dudas, A.; Beke, D.

In: Vacuum, Vol. 85, No. 4, 21.10.2010, p. 493-497.

Research output: Contribution to journalArticle

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AU - Csík, A.

AU - Dudas, A.

AU - Beke, D.

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AB - Proper understanding of the degradation mechanisms and diffusion kinetics of copper and cobalt interconnections for advanced microelectronics is important from the point of view of fundamental research and technology as well. In this paper Si(substrate)/Ta(10 nm)/Cu(25 nm)/W(10 nm) and Si(substrate)/Co(150 nm)/Ta(10 nm) samples, prepared by DC magnetron sputtering, were in investigated. The samples were annealed at several temperatures ranging from 423 K to 823 K for various times. The composition distributions were detected by means of Secondary Neutral Mass Spectrometry (SNMS). Microstructural characterization of samples was carried out by means of Transmission Electron Microscopy (TEM). It is shown that the changes in the composition profiles were mainly caused by grain boundary, GB, diffusion and the effective GB diffusion coefficients of Ta in Cu were determined both by the "first appearance" and "centre-gradient" methods. The activation energy is 100 kJ/mol. The importance of the Ta penetration into the Cu and its accumulation at the Cu/W interface can lead to an increase of the Ta content in the copper film. This can be an important factor in the change/degradation of the physical parameters (e.g. the electrical resistance) of interconnects. Furthermore a Ta segregation factor in Cu was evaluated. Preliminary results in the Si(substrate)/Co(150 nm)/Ta(10 nm) indicate fast (GB) diffusion of the Si into the Co layer, formation of a cobalt silicide layer at the Co/Si interface and Si accumulation first at the Ta/Co interface and later a retarded accumulation at the free Ta surface.

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