Investigation of the fracture of very thin amorphous alumina film during spherical nanoindentation

David Mercier (1) , Vincent Mandrillon (1) , Guillaume Parry (2) , Marc Verdier (2) , Rafael Estevez (2) , Yves Brechet (2) , Tony Maindron (1)

1 CEA-LETI - Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information
2 SIMaP - Science et Ingénierie des Matériaux et Procédés

Thin amorphous alumina layers (10 to 40 nm thick) are processed on sputtered aluminum thin film (500 nm) by atomic layer deposition (ALD) at low temperature (85 °C). Global methodology combining quantitative experimental observations of fracture and numerical modeling is proposed to obtain the fracture strength of ALD thin film on Al layer. First, mechanical properties of the multilayer specimen are characterized by Berkovich nanoindentation, then fracture of ALD alumina is studied through spherical indentation with various tip radius. Spherical indentation load driven-displacement curves display a plateau (pop-in) at a critical load and critical indentation depth. A statistical approach is used to determine pertinent/fracture parameters from pop-in displacement. Careful SEM and AFM observations of indentation imprint exhibit circumferential cracking in agreement with the assumption that the pop-in event is predominantly controlled by the fracture of the oxide layer on the soft Al film. Finally, a numerical model calibrated with experimental results is used in order to predict both the mechanical response prior to the oxide fracture and a value of fracture strength for ALD alumina thin films.

Mots clés: thin hard film; ALD alumina; nanoindentation; cracks; pop-in; Weibull statistical analysis; finite element modeling; fracture strength

Domaines: Mécanique des matériaux [physics.class-ph]

David Mercier, Vincent Mandrillon, Guillaume Parry, Marc Verdier, Rafael Estevez, et al.. Investigation of the fracture of very thin amorphous alumina film during spherical nanoindentation. Thin Solid Films, 2017, 638, pp.34-47. ⟨10.1016/j.tsf.2017.07.040⟩. ⟨hal-01685489⟩