Influence of apparatus geometry and deposition conditions on the structure and topography of thick sputtered coatings

TLDR

Previous work on metal deposition (Movchan and Demchishin, 1969) provides the foundational context for this study. Two sputtering geometries—post and hollow cathodes—were employed to deposit ~25‑µm thick metal coatings at 1000–2000 Å min⁻¹, with the resulting microstructures characterized by SEM, metallography, and X‑ray diffraction. The coatings followed the Movchan–Demchishin three‑zone model, exhibiting a broad fibrous transition zone at low argon pressure, temperature‑dependent faceting of zone 2 grains, no zone 3 equiaxed grains, and enhanced intergrain shading when deposited with the hollow cathode.

Abstract

Two cylindrically symmetric and complementary sputtering geometries, the post and hollow cathodes, were used to deposit thick (∼25-μ) coatings of various metals (Mo, Cr, Ti, Fe, Cu, and Al-alloy) onto glass and metallic substrates at deposition rates of 1000–2000 Å/min under various conditions of substrate temperature, argon pressure, and plasma bombardment. Coating surface topographies and fracture cross sections were examined by scanning electron microscopy. Polished cross sections were examined metallographically. Crystallographic orientations were determined by x-ray diffraction. Microstructures were generally consistent with the three-zone model proposed by Movchan and Demchishin [Fiz. Metal. Metalloved. 28, 653 (1969)]. Three differences were noted: (1) at low argon pressures a broad zone 1–zone 2 transition zone consisting of densely packed fibrous grains was identified; (2) zone 2 columnar grains tended to be faceted at elevated temperatures, although facets were often replaced by smooth flat surfaces at higher temperatures; (3) zone 3 equiaxed grains were generally not observed at the deposition conditions investigated. Hollow cathode deposition accentuated those features of coating growth that relate to intergrain shading.