SEM <I>In Situ</I> Study on Deformation Behavior of Cu and Cu/Ni Films under Three-Point Bending

Abstract

The deformation and failure of Cu and Cu/Ni film/substrate structure were studied by the scanning electron microscope (SEM) in situ observation under three-point bending. It was found that the rapid deformation occurred at sites near to the interface of film/substrate in Cu and Cu/Ni films. The transferring of deformation finally caused the surface wrinkle. The wrinkle stress can be expressed asBased on the results in mesoscale, a simple failure mechanism of films/substrate structure is suggested to understand the transferring process of deformation and failure characteristics.

SEM in-situ investigation on failure of nanometallic film/substrate structures under three-point bending loading

“…Therefore, the delaminated failure of the thin film from the substrate occurred easily at the interface when the scratch load exceeded the critical loading L c . In addition to the effect of interfacial strength on the failure model of film/substrate structure, the residual stress in the thin film may also be one of the reasons for earlier damage of the film/substrate structure, such as the void formation and delamination at the film/substrate interface (Stoney 1909;Gao and Nix 1999;Chen and Hon 2002), and plastic deformation of the thin film (Huang et al 2007). At the same time, the adhesion strength is also affected by the residual stress in the film, leading to a decrease of stability and reliability of MEMS (Yu et al 2006).…”

“…A Cu substrate was used to minimize the effect of Young's modulus mismatch between the thin film and the substrate on the cracking or deformation at the interface. The grain size of the nanocrystal Cu in the film was about 11.96 nm and the Cu film presented a strong <111> texture along the film growth direction, indicated by X-ray diffraction (XRD) (Huang et al 2007). The grain size of the nanocrystal Ni in the Cu/Ni films was about 17.37 nm.…”

“…The thickness of the Cu/Ni multi-layered thin films was about 2 µm. The typical X-ray diffraction (XRD) patterns of the Cu/Ni multi-layered thin films are shown in Huang et al (2007).…”

“…But, the layered structure also leads to issues of reliability resulting from different failure mechanisms, such as delamination at the interface, cracking of thin films, or morphological instability and fatigue damage initiating at the surface or interface of thin films during device fabrication, testing or operation (Schwaiger and Kraft 1999;Kraft et al 2001;Zhang and Zhao 2002). A few special failure modes of thin film/substrate structure were reported based on theoretical analysis and experimental observations (Wang et al 2002(Wang et al , 2004aXiang et al 2005;Li and Suo 2006;Dkhil et al 2007;Huang et al 2007;Wu et al 2007). Unfortunately, almost none of these works focused on the cracking evolutions of the thin film/substrate structure, especially the failure mechanism of the thin film/substrate structure at the mesoscale, where damage initiates.…”

Evaluation of the critical stress of anodized coating-AZ91D substrate using SEM in-situ technology

“…A signal from the SEM was directly transferred to a computer via a direct memory access type A/D converter, making it possible to sample 9601280 frames of SEM images successively in in-situ observation during the bending test. All bending tests were controlled by a stroke ratio of 10 −4 mm/min Wang and Fan, 2006;Huang et al, 2007;Jia et al, 2012;Ren et al, 2013;Ren and Wang, 2014).…”