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Copper Diffusion Characteristics in Single Crystal and Polycrystalline TaN

Published online by Cambridge University Press:  11 February 2011

H. Wang ,
Ashutosh Tiwari ,
X. Zhang ,
A. Kvit  and
J. Narayan
H. Wang
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7916
Ashutosh Tiwari
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7916
X. Zhang
Affiliation:
Materials Science & Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544
A. Kvit
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7916
J. Narayan
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7916
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Abstract

TaN has become a very promising diffusion barrier material for Cu interconnections, due to the high thermal stability requirement and thickness limitation for next generation ULSI devices. TaN has a variety of phases and Cu diffusion characteristics vary with different phases and microstructures. We have investigated the diffusivity of copper in single-crystal (NaCl-structured) and polycrystalline TaN thin films grown by pulsed laser deposition. The polycrystalline TaN films were grown directly on Si(100), while the single crystal films were grown with TiN buffer layers. Both of poly and single-crystal films with Cu overlayers were annealed at 500 °C, 600 °C, 650 °C, and 700 °C in vacuum to study the copper diffusion characteristics. The diffusion of copper into TaN was studied using STEM-Z contrast, where the contrast is proportional to Z (atomic number), and TEM. The diffusion distances are found to be about 5nm at 650°C for 30 min annealing. The diffusivity of Cu into single crystal TaN follows the relation D = (160±9.5)exp[-(3.27 ±0.1)eV/kBT]cm2s-1 in the temperature range of 600°C to 700°C. We observe that Cu diffusion in polycrystalline TaN thin films is nonuniform with enhanced diffusivities along the grain boundary.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 745: Symposium N – Novel Materials and Processes for Advanced CMOS , 2002 , N6.11
Copyright
Copyright © Materials Research Society 2003

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References

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