Effects of Oxygen on the Properties of Sputtered Molybdenum Thin Films

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Abstract
The effects of oxygen on film structures and film stresses of sputtered Mo thin films have been investigated. Mo films (8000 Å) were deposited on Si(111) wafers in 0.4 Pa using Ar or Ar+O2 (O2 partial pressure: 0.01 Pa) working gases at 423 K. The major impurity was oxygen, and argon content was below the detection limit (0.05 at.%) of the fluorescence X-ray analysis. Microstructure and film stresses were affected by oxygen. The fibrous grain width in the films was decreased from 40-130 nm with 2.4 at.% oxygen to 40-70 nm with 14.4 at.% oxygen. The high tensile stress, 1×1010 (dyn/cm2) with 2.4 at.% oxygen, changed to the low compressive stress, 1.0×109 (dyn/cm2) with 30.1 at.% oxygen. This paper discusses the relationships between oxygen content and the film structures, and between oxygen content and the film stresses.