Mechanical Properties of Thin Films

Alexopoulos, P.; O'Sullivan, Tadhg

doi:10.1146/annurev.ms.20.080190.002135

Cited by 84 publications

(35 citation statements)

References 2 publications

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“…We expect that a similar model would provide a good description of the flow stress as a function of temperature. The diffusion-facilitated grain boundary sliding mechanism is also consistent with the observation that the 960 nm film is much stronger than the 450 nm film (Table II), in contrast to the usual notion that smaller is stronger where thin films are concerned [9][10][11]. Within the context of the Ashby model, this anomaly is readily explained as a grain size effect.…”

Section: Discussionsupporting

confidence: 83%

“…As a result, metal thin films, which are key components in these devices, have been studied extensively. These investigations have demonstrated that the mechanical properties of thin films are generally very different from those of their bulk counterparts [1][2][3][4][5][6][7][8][9][10][11] and that they depend on whether the film is freestanding or supported by a substrate [12][13][14][15]. Understanding the mechanical behavior of metal thin films at elevated temperature is essential for the design of reliable devices, which often operate above room temperature.…”

Section: Introductionmentioning

confidence: 99%

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High-temperature tensile behavior of freestanding Au thin films

Sim

Vlassak

2014

Scripta Materialia

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The mechanical behavior of freestanding thin sputter-deposited films of Au is studied at temperatures up to 340°C using tensile testing. Films tested at elevated temperatures exhibit a significant decrease in flow stress and stiffness. Furthermore the flow stress decreases with decreasing film thickness, contravening the usual notion that "smaller is stronger". This behavior is attributed mainly to diffusion-facilitated grain boundary sliding.Keywords: In situ tensile test, High-temperature deformation, Thin films, Grain boundary sliding, Creep IntroductionThe decreasing size of microelectronics devices has motivated a strong interest in the effects of length scales on the mechanical behavior of thin films of metal. As a result, metal thin films, which are key components in these devices, have been studied extensively. These investigations have demonstrated that the mechanical properties of thin films are generally very different from those of their bulk counterparts [1][2][3][4][5][6][7][8][9][10][11] and that they depend on whether the film is freestanding or supported by a substrate [12][13][14][15]. Understanding the mechanical behavior of metal thin films at elevated temperature is essential for the design of reliable devices, which often operate above room temperature. Several studies have been performed on the high-temperature behavior of films on substrates [2,[16][17][18][19], but studies on freestanding films have been limited to temperatures below 200ºC [20][21][22][23] due to difficulties associated with sample handling, oxidation, and temperature uniformity in the sample. The few studies performed at higher temperatures focused on films that were several microns thick [24][25][26]. Thus, the high-temperature behavior of freestanding metal thin films is still relatively unexplored. Recently, we developed a technique for the tensile testing of freestanding thin films in which samples were mounted on a micro-machined silicon frame with integrated heaters [27]. The samples were deformed in-situ inside a scanning electron microscope (SEM) by means of a custom-built test apparatus. Using this technique, the stress-strain curves of copper thin films were measured at temperatures up to 430°C. In this paper, the same technique is used to characterize the mechanical behavior of gold films as a function of temperature and strain rate. Gold was chosen as the material of interest due to its oxidation resistance and low electrical resistivity. The oxidation resistance makes gold an interesting material for studying the inherent mechanical behavior at elevated temperature without the added complication of a passivation

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

High-temperature tensile behavior of freestanding Au thin films

Sim

Vlassak

2014

Scripta Materialia

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“…66,70,71 The mechanical properties of UTCs differ from their bulk counterparts due to differences in processing, size, material composition, and microstructure. [72][73][74] A comparison of Young's modulus E and the Poisson's ratio 68 of several materials frequently used in flexible electronics [e.g., singlecrystal Si, hydrogenated amorphous (a-Si:H), hydrogenated nanocrystalline Si (nc-Si:H), polycrystalline Si, Kapton V R , and polyethylene naphthalate (PEN)] is given in Table I. [75][76][77][78][79][80][81][82] The experimental techniques that have been used to study mechanical aspects of UTCs include (i) direct methods 83,84 such as xray diffraction 85,86 and micro-Raman spectroscopy 87,88 and (ii) indirect methods based on measuring the curvature 89 (e.g., optical interferometry, 90 laser scanning, 91,92 and microscope image monitoring in real time 43 ).…”

Section: Ultra-thin Chips and Mechanical Bendingmentioning

confidence: 99%

Bending induced electrical response variations in ultra-thin flexible chips and device modeling

Heidari

Wacker

Dahiya

2017

Applied Physics Reviews

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Electronics that conform to 3D surfaces are attracting wider attention from both academia and industry. The research in the field has, thus far, focused primarily on showcasing the efficacy of various materials and fabrication methods for electronic/sensing devices on flexible substrates. As the device response changes are bound to change with stresses induced by bending, the next step will be to develop the capacity to predict the response of flexible systems under various bending conditions. This paper comprehensively reviews the effects of bending on the response of devices on ultra-thin chips in terms of variations in electrical parameters such as mobility, threshold voltage, and device performance (static and dynamic). The discussion also includes variations in the device response due to crystal orientation, applied mechanics, band structure, and fabrication processes. Further, strategies for compensating or minimizing these bending-induced variations have been presented. Following the in-depth analysis, this paper proposes new mathematical relations to simulate and predict the device response under various bending conditions. These mathematical relations have also been used to develop new compact models that have been verified by comparing simulation results with the experimental values reported in the recent literature. These advances will enable next generation computer-aided-design tools to meet the future design needs in flexible electronics.

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“…Several studies and reviews of the mechanical behavior of thin films have appeared in the literature (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). These show the variety of test techniques that have been developed, and results that have been obtained.…”

Section: Mechanical Testing Of Thin Filmsmentioning

confidence: 99%