The influence of chemistry on the interface toughness in a WTi-Cu system

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Abstract

With a considerable amount of commonly used material systems consisting of individual, rather confined layers, the question for mechanical behaviour of their individual interfaces arises. Especially, when considering varying interfacial structures as a result of the processing environment. Furthermore, the interaction between pronounced plasticity and fracture processes can lead to challenges with regards to separation between sole interface- or bulk properties.

The present work investigates the interfacial fracture characteristic of a WTi-Cu sytem commonly found in the microelectronics industry as a heterogeneous model material with pronounced plasticity in the Cu phase. To study this behaviour on a rather limited scale (<6 µm), microcantilever experiments were conducted and evaluated using a continuous J-Δa curve evaluation scheme with classical elastic-plastic considerations in mind. A change in interface chemistry, resulting from air exposure between processing steps, was probed and found to show distinct crack propagation along the interface opposed to crack tip blunting as encountered in the vacuum processed sample. Complementary density functional theory calculations also showed a strong reduction of interface cohesion upon oxygen accumulation and a model framework based on classical dislocation plasticity considerations revealed the transition from plasticity to fracture processes to be a result of shielding and following change in mode mixity.
Original languageEnglish
Article number117813
Number of pages13
JournalActa Materialia
Volume230.2022
Issue number15 May
Early online date5 Mar 2022
DOIs
Publication statusPublished - 15 May 2022

Bibliographical note

Publisher Copyright: © 2022

Keywords

  • Crack extension
  • Density functional theory
  • Interface toughness
  • Thin films

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