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Effect of Nitrogen Diffusion in Ti and TiTiN Films for Future DRAM Bit Line Interconnects and Plugs

Published online by Cambridge University Press:  10 February 2011

John M. Drynan
Affiliation:
ULSI Device Development Laboratories, NEC Corporation 1120 Shimokuzawa, Sagamihara, Kanagawa 229, JAPAN
Kuniaki Koyama
Affiliation:
ULSI Device Development Laboratories, NEC Corporation 1120 Shimokuzawa, Sagamihara, Kanagawa 229, JAPAN
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Abstract

The effects of nitrogen diffusion from both N2 gas phase and TiN solid phase sources on the characteristics of Ti/TiN bilayer and TiN/Ti/TiN trilayer films have been investigated in terms of both materials properties such as resistance, coloration, composition, and crystallinity, and prospective applications such as for DRAM bit line interconnections and contact-hole plugs. Using blank films it has been found, in coincidence with other work, that at the onset of N diffusion and hence low N concentrations within a Ti film, the sheet resistance increases and the Ti layer becomes a solid solution of N in hexagonal Ti. As the concentration increases, the sheet resistance reaches a maximum, after which it decreases abruptly and the structure becomes primarily tetragonal Ti2N phase. At higher concentrations the resistance stabilizes or increases slightly and the structure becomes more cubic TiN phase. Sheet resistances calculated from resistance measurements of Ti and TiN mono- and multilayer conductor lines with and without RTN and RTAr thermal treatments have shown that the conductor lines exhibit similar behavior to the blank films. In comparison with the mon-olayer lines, the multilayer ones are generally lower in resistance and more stable over a wider range of post-deposition process temperatures.

Type
Research Article
Copyright
Copyright © Materials Research Society 1996

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