Stress evolution in magnetron sputtered Ti–Zr–N and Ti–Ta–N films studied by in situ wafer curvature: Role of energetic particles

• Published in: Thin solid films 2009-12, Vol.518 (5), p.1532-1537
• Main Authors: Abadias, G., Koutsokeras, L.E., Guerin, Ph, Patsalas, P.
• Format: Article
• Language: English
• Subjects: Gradients; In situ; Magnetron sputtering; Stress; TaN; Ternary nitride; TiN; ZrN
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2009.07.183

Stress evolution during reactive magnetron sputtering of binary TiN, ZrN and TaN thin films as well as ternary Ti–Zr–N and Ti–Ta–N solid-solutions was studied using real-time wafer curvature measurements. The energy of the incoming particles (sputtered atoms, backscattered Ar, ions) was tuned by changing either the metal target (MTi=47.9, MZr=91.2 and MTa=180.9g/mol), the plasma conditions (effect of pressure, substrate bias or magnetron configuration) for a given target or by combining different metal targets during co-sputtering. Experimental results were discussed using the average energy of the incoming species, as calculated using Monte-Carlo simulations (SRIM code). In the early stage of growth, a rapid evolution to compressive stress states is noticed for all films. A reversal towards tensile stress is observed with increasing thickness at low energetic deposition conditions, revealing the presence of stress gradients. The tensile stress is ascribed to the development of a ‘zone T’ columnar growth with intercolumnar voids and rough surface. At higher energetic deposition conditions, the atomic peening mechanism is predominant: the stress remains largely compressive and dense films with more globular microstructure and smooth surface are obtained.