Real-time stress evolution during early growth stages of sputter-deposited metal films: Influence of adatom mobility

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• 作者：G. Abadias ; A. Fillon ; J.J. Colin ; A. Michel ; C. Jaouen
• 关键词：Stress ; Sputtering ; Metallic films ; Surface diffusivity ; Interface stress ; Coalescence ; Nucleation and growth
• 刊名：Vacuum
• 出版年：2014
• 出版时间：February, 2014
• 年：2014
• 卷：100
• 期：Complete
• 页码：36-40
• 全文大小：799 K

文摘

Using a multi-beam optical stress sensor, the real-time stress evolution during the early growth stages of a large class of sputter-deposited metal (Me) films is studied with monolayer sensitivity. For high-mobility fcc (Ag, Au, Pd) metals, a typical compressive-tensile-compressive (CTC) behavior is observed, characteristic of a Volmer-Weber growth mode. A correlation between the homologous temperature (T_s/T_m), tensile stress peak position, grain size and steady-state compressive stress in the post-coalescence stage is presented. For low-mobility bcc (Mo, W, Ta) metals (T_s/T_m?¡Ü?0.10) deposited on a-Si, kinetic limitations result in a 2D growth mode highly influenced by interfacial effects. The film force is initially dominated by change in surface stress, which scales with the surface energy difference ¦¤¦Ã?=?¦Ã_Me???¦Ã_a-Si. For both Mo and W, a stress transient is observed in the 2-4?nm range, followed by the development of unexpectedly large tensile stress, ascribed to a phase transition towards their equilibrium ¦Á-Mo and ¦Á-W structure. Such transient is not evidenced during Ta growth for which a compressive stress regime is steadily established and related to the growth of its metastable ¦Â-Ta structure. For all low-mobility metals, the final stress regime is controlled by the energetics of the incoming species and intrinsic mechanical properties of the material.