Nanoindentation study of elastic anisotropy of Cu single crystals and grains in TSVs

This paper presents the results of nanoindentation experiments on Cu single crystals and Cu grains in through silicon via (TSV) structures used for 3D integrated circuit (IC) stacking, at sub-10nm and several-10nm penetration depths. The reduced moduli for Cu single crystals change from an average value to the uni-directional values, as the penetration depths decrease from several-10nm to sub-10nm. At sub-10nm deformation, about one third of the indentations on Cu(111) and Cu(110) show fully elastic behavior, while all indentations on Cu(100) shows elastic-plastic behavior. The reduced modulus values extracted from indents on Cu(111) and Cu(110) with fully elastic behavior are about 195GPa and 145GPa, respectively. For penetration depths of several-10nm up to 50nm, the reduced modulus for Cu(100) varies between 50GPa to 100GPa. The averaged reduced moduli determined at relatively large penetration depths are explained with lattice rotation beneath the indentations. Sinc e the activation of multiple slip systems is required for lattice rotation, the transition of the unidirectional reduced modulus to the averaged value with increasing penetration depths occurs differently for Cu(111) and Cu(100). Similar to the results from Cu single crystals, unidirectional reduced moduli are obtained for the Cu grains in TSV structures at sub-10nm penetration depths

Adhesion studies by instrumental indentation testing

The miniaturization of devices and the advances in nanotechnol.-enabled products has led to the requirement of an increased understanding of the various interactions present in nanoscale contacts - including adhesion and surface tension. It is well known that adhesion plays an important role in the tribol. behavior and contact mechanics of many modern nano-devices and will affect future products currently under development. Adhesion of materials is ruled by interactions that extend down to the at. scale of the contributing materials. The forces involved include non-covalent interactions such as Van-der-Waals forces, hydrogen bonds and Coulomb forces as well as covalent chem. bonds. Although Van-der-Waals forces are only short range, they often rule the adhesion between two materials and are therefore responsible for contact interaction between two films. While the adhesion between two materials is one important factor, the elasticity of both is also very important. This elasticity has a major influence on the size of a contact area that is developed underneath a point contact when a certain force is active. Modern instruments for nanoindentation are sensitive enough to detect the small surface forces and to study adhesion effects. [on SciFinder (R)

Mechanical Properties of Organic Electronic Polymers on the Nanoscale

Organic semiconducting polymers have attractive electronic, optical, and mechanical properties that make them materials of choice for large area flexible electronic devices. In these devices, the electronically active polymer components are micrometers in size, and sport negligible performance degradation upon bending the centimeter-scale flexible substrate onto which they are integrated. A closer look at the mechanical properties of the polymers, on the grain-scale and smaller, is not necessary in large area electronic applications. In emerging micromechanical and electromechanical applications where the organic polymer elements are flexed on length scales spanning their own micron-sized active areas, it becomes important to characterize the uniformity of their mechanical properties on the nanoscale. In this work, the authors use two precision nanomechanical characterization techniques, namely, atomic force microscope based PeakForce quantitative nanomechanical mapping (PF-QNM) and nanoindentation-based dynamical mechanical analysis (nano-DMA), to compare the modulus and the viscoelastic properties of organic polymers used routinely in organic electronics. They quantitatively demonstrate that the semiconducting near-amorphous organic polymer indacenodithiophene-co-benzothiadiazole (C16-IDTBT) has a higher carrier mobility, lower modulus, and greater nanoscale modulus areal uniformity compared to the semiconducting semicrystalline organic polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (C14-PBTTT). Modulus homogeneity appears intrinsic to C16-IDTBT but can be improved in C14-PBTTT upon chemical doping.SCOPUS: ar.jinfo:eu-repo/semantics/publishe