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Control of Microstructure and Stress in Sputtered Tungsten Thin Films on Silicon

Published online by Cambridge University Press:  26 February 2011

R.R. Kola  and
G.K. Celler
R.R. Kola
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
G.K. Celler
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
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Abstract

Tungsten is attractive for VLSI device metallization because of its high conductivity and resistance to interdiffusion and electromigration. It is also one of the best absorber metals for x-ray lithographic masks. To minimize distortions in an x-ray mask, intrinsic stresses in the absorber films have to be low and reproducible. The physical properties of thin films are very dependent on their microstructure. We present the results of a study of the microstructural evolution and the resulting internal stress of rf sputter-deposited W films as a function of rf power, deposition temperature, and argon pressure. By controlling the nucleating phase and mobility of the adatoms, we have produced W films with low stresses (<±50 MPa). The lattice parameter and the argon content in W films increased with decreasing argon deposition pressure. It was found that a low base pressure (<10−7 torr) is necessary to produce stable α-phase W and to eliminate the metastable β-phase. Stresses in the W films were not affected bysubsequent anneals in vacuum at 200 °C for 50 hrs. In-situ stress measurements indicated stress relaxation by plastic deformation above 300 °C.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 226: Symposium H – Mechanical Behavior of Materials and Structures in Microelectronics , 1991 , 235
Copyright
Copyright © Materials Research Society 1991

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