Fracture Properties and Residual Stresses in Small Dimensions: Interface Dominated Fracture
Sponsored by: TMS Structural Materials Division, TMS Materials Processing and Manufacturing Division, TMS: Mechanical Behavior of Materials Committee, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Daniel Kiener, University of Leoben; Marco Sebastiani, Roma TRE university; Nagamani Jaya Balila, Max Planck Institut fuer Eisenforschung GmbH; William Gerberich, University of Minnesota; Siddhartha (Sid) Pathak, University of Nevada, Reno

Thursday 2:00 PM
March 2, 2017
Room: 21
Location: San Diego Convention Ctr

Session Chair: Rafael Soler, MPIE; Nan Li, Los Alamos National Laboratory

2:00 PM  Invited
Temperature-Dependent Delamination Failure of Metal-Ceramic Interfaces: Rafael Soler1; Sriram Venkatesan1; Johannes Zechner2; Michael Nelhiebel2; Roman Roth3; Josef Fugger2; Gerhard Dehm1; 1Max-Planck-Institut für Eisenforschung GmbH; 2KAI - Kompetenzzentrum Automobil- und Industrieelektronik; 3Infineon Technologies AG
    Delamination failure in modern microelectronic devices, where complex multi-layered structures are common, is known to be usually driven by thermal expansion mismatch stresses, both produced during the thin film fabrication process and during device operation (where multiple loading condition, e.g. temporal and spatial temperature gradients, are induced). In this work we shed some light on the delamination behavior of such complex structures under service temperatures, i.e. up to 400 °C. We analyse the temperature dependency on the interface strength of bimaterial interfaces. The study focuses on various metal-ceramic interfaces, namely between a metallization layer (W, Ti, or Cu) and a borophosphosilicate glass (BPSG). The mechanical experiments are conducted by both, macro- and micro-scale approaches, i.e. 4-point-bending and single beam cantilever experiments, respectively. The temperature-dependent delamination behavior will be discussed with respect to the microstructural and chemical evolution from pre- and post-mortem samples.

2:30 PM  
Oxide-induced Substrate Cracking in Ti and Stainless Steels Driven by Pulsed Laser Irradiation: Jesus Morales Espejo1; David Bahr1; 1Purdue University
    Oxide layers grown on Ti6Al4V and 304 stainless steel using pulsed laser irradiation (PLI) at different scan rates on samples were analyzed. These oxides exhibit mudflat cracking, with an increasing crack density formed at faster laser scan rates. The mudflat cracks penetrate into the substrate of both materials, with crack depths between 1 – 6 μm. The cracks do not appear to be significantly influenced by the underlying substrate grain orientation. Residual stresses in the oxides were estimated using several methods. With the elastic and fracture properties of film measured using nanoindentation, a low substrate toughness is inferred, likely due to embrittlement promoted by hydrogen penetrating into the film and substrate during oxide growth; compositional depth profiles were carried out to explain this behavior. An understanding of the cracking phenomenon induced by PLI on both materials and possible mitigation mechanisms will be presented.

2:50 PM  
Fracture Toughness of Beryllium Using Insitu X-ray and Digital Image Correlation Techniques: Carl Cady1; Cheng Liu1; George Gray1; Neil Bourne2; 1Los Alamos National Laboratory; 2University of Manchester
    The primary reason for this investigation was to measure the fracture toughness on beryllium and observe crack growth using in-situ an x-ray characterization technique and digital image correlation. The fracture toughness was evaluated by using a “compression-fracture” introduced by Sammis and Ashby. Two experimental techniques were used to captured deformation and damage. An in-situ x-ray tomography technique was used for the internal fracture processes and digital image correlation for the surface evaluation. The development of technique to evaluate strain fields using linear elastic fracture mechanics provides consistent results that are typical of the standard fracture toughness evaluation. Further development in the characterization using continuum mechanics has led to a solution that more closely resembled the standard compact tension problem. In this solution we have been able to extract the modulus values and Poisson’s ratio form the experimental analysis and make corrections to the solution that minimizes errors.