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The Electromigration of CVD-Copper and PVD-Copper Polycrystalline Lines

Published online by Cambridge University Press:  10 February 2011

Seok Kim  and
Doo-Jin Choi
Seok Kim
Affiliation:
Dept. of Ceramic Engr., Yonsei Univ., Seoul, Korea120-749
Doo-Jin Choi
Affiliation:
Dept. of Ceramic Engr., Yonsei Univ., Seoul, Korea120-749
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Abstract

The electromigration characteristics of CVD-Cu films were compared to those of PVDCu films. The CVD-Cu films were deposited using metal-organic precursor of (hfac)Cu(VTMS) and the PVD-Cu films were deposited by evaporation of a 99.995 % Cu metal on TiN and SiO2 substrates. To test EM-resistance, Cu film was patterned into the test structure of multi-lines with 20∼30 µm width and 2500 µm length per one line by a photolithography technique. These test lines had polycrystalline structures composed of much smaller grains than line width and thickness. An accelerated EM test was carried out in the vacuum of 10−6 Torr because the test in N2 ambient had lead to a resistance increase mainly due to oxidation of Cu.

The CVD-Cu lines had shorter lifetime than PVD-Cu and the activation energy of electromigration was 0.754 eV for the CVD-Cu on SiO2, which means the grain boundary diffusion as the EM failure mechanism. The CVD-Cu films had larger grains and poorer continuity between grains than the PVD-Cu films so the resistivity of CVD-Cu films (3.20±0.21 µΩcm) was higher than that of PVD-Cu films (2.00±0.06 µΩcm) having a value of near bulk resistivity. The higher resistivity induces the higher driving force of EM. Moreover the PVD-Cu films had a huge domain structure, which might act as a larger grain than CVD-Cu grain to result in the longer life-time and the surface diffusion mechanism with the activation energy of 0.244 eV.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 516: Symposium E – Low Dielectric Constant Materials IV , January 1998 , 281
Copyright
Copyright © Materials Research Society 1998

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