Observation of nano-indent induced strain fields and dislocation generation in silicon wafers using micro-raman spectroscopy and white beam x-ray topography

In the semiconductor manufacturing industry, wafer handling introduces micro-cracks at the wafer edge. During heat treatment these can produce larger, long-range cracks in the wafer which can cause wafer breakage during manufacture. Two complimentary techniques, micro-Raman spectroscopy (μRS) and White Beam Synchrotron X-ray Topography (WBSXRT) were employed to study both the micro-cracks and the associated strain fields produced by nano-indentations in Si wafers, which were used as a means of introducing controlled strain in the wafers. It is shown that both the spatial lateral and depth distribution of these long range strain fields are relatively isotropic in nature. The Raman spectra suggest the presence of a region under tensile strain beneath the indents, which can indicate a crack beneath the indent and the data strongly suggests that there exists a minimum critical applied load below which cracking will not initiate

Mechanical Deformation Induced in Si and GaN Under Berkovich Nanoindentation

Details of Berkovich nanoindentation-induced mechanical deformation mechanisms of single-crystal Si(100) and the metal-organic chemical-vapor deposition (MOCVD) derived GaN thin films have been systematic investigated by means of micro-Raman spectroscopy and cross-sectional transmission electron microscopy (XTEM) techniques. The XTEM samples were prepared by using focused ion beam (FIB) milling to accurately position the cross-section of the nanoindented area. The behaviors of the discontinuities displayed in the loading and unloading segments of the load-displacement curves of Si and GaN thin films performed with a Berkovich diamond indenter tip were explained by the observed microstructure features obtained from XTEM analyses. According to the observations of micro-Raman and XTEM, the nanoindentation-induced mechanical deformation is due primarily to the generation and propagation of dislocations gliding along the pyramidal and basal planes specific to the hexagonal structure of GaN thin films rather than by indentation-induced phase transformations displayed in Si

Molecular Dynamics Simulation of Nanoindentation-induced Mechanical Deformation and Phase Transformation in Monocrystalline Silicon

This work presents the molecular dynamics approach toward mechanical deformation and phase transformation mechanisms of monocrystalline Si(100) subjected to nanoindentation. We demonstrate phase distributions during loading and unloading stages of both spherical and Berkovich nanoindentations. By searching the presence of the fifth neighboring atom within a non-bonding length, Si-III and Si-XII have been successfully distinguished from Si-I. Crystallinity of this mixed-phase was further identified by radial distribution functions

Besser und günstiger Walzen mit Werkzeugen und Komponenten aus Hochleistungskeramik

In der Walztechnik besteht ein erhöhter Bedarf an verschleiß- und korrosionsbeständigen, mechanisch und thermisch hoch belastbaren Komponenten. Im Rahmen eines Verbundprojekts [1] wurden keramische Werkzeuge und Komponenten für die Walztechnik entwickelt, um die Wirtschaftlichkeit, Produktqualität und Ressourceneffizienz von Walzprozessen zu verbessern

A wear model for silicon nitride in dry sliding contact against a nickel-base alloy

The properties of silicon nitride ceramics allow their broad application in extreme tribological conditions. High-temperature sliding contact of Si3N4-base materials against metals will be found more often in future applications, in which the ceramic's wear resistance becomes clearly necessary. In this study, the dry sliding behavior of silicon nitride against Inconel 718 is investigated. Wear experiments were carried out at sliding velocities ranging from 1 to 20 m/s. A finite element wear simulation was constructed by relying on experimentally measured wear rates and COF. The simulations enabled quantifying localized temperature and contact stress fields as a function of geometrical changes due to progressive wear. The experiments showed a transition in wear mechanisms depending on the sliding velocity and frictional power. Cross-sectional analysis of the ceramic samples provided information on the tribochemical processes and the dominant wear mechanisms. Combining analytical and numerical results enabled proposing a schematic wear model. The agreement of this model with common theories of wear is discussed

Relationship between ultralow friction of mesogenic-like fluids and their lateral chain length

Mesogenic fluids (MFs) may have a great potential for technical applications to increase the energy efficiency and to prevent wear. Aim of the present work was to study a homologous series of mesogenic-like fluids to evaluate the influence of the chemical structure on the tribological behavior. Rheological measurements were additionally performed to correlate the tribological properties with the viscosity and flow behavior. Raman spectroscopy and differential scanning calorimetry measurements were used to characterize the MFs. Furthermore, the surface topography of the wear scar was studied by profilometry. The results were summarized and hence an approach was made to describe the several mechanisms which may lead to the observed tribological results. This work shows that a better understanding of the tribological behavior of these MFs is essential to develop new lubricants

Silicon nitride wire rolling tools: Damage analysis and correlation with rolling-contact fatigue

Failure mechanisms of silicon nitride wire rolling tools used in forming high strength steels were investigated. Wire rolling experiments and FEM were carried out to analyze the thermomechanical loading in this metalforming process. Based on the experimental observations and numerical computations, a model was proposed to describe the failure mechanisms in work rolls. Thermal stresses were found to comprise a minuscule portion of the overall thermomechanical stresses developed in the rolls. Surface wear played a fundamental and decisive role in the damage evolution and lifetime of the rolling tools. Tensile stress, which is relevant to the fracture of Si3N4, exhibited a peak on the caliber flanks. Both the value and location of this peak were found to be dependent on wire reduction. Furthermore, failure of Si3N4 rolls under rolling-contact fatigue was investigated by means of twin-disk experiments and FEM. The results emphasized the impact of tribomechanical aspects on the failure of ceramic components. Such observations could be transferred to wire rolling to improve the reliability of ceramic-based rolling tools

Using ceramics for wear resistant metal working tools: Ceramic rolls for wires, tubes and sheets

Thanks to their high wear resistance, ceramic materials are suited for use as forming rolls. In collaboration with manufacturing and machining companies, as well as users, the ceramic tools are developed, manufactured and tested. The main goal of the project is to enhance the lifetime of the rolling toots significantly. In addition, more stable production conditions may be obtained and the use of cooling lubricants can be reduced