Investigation of moisture-assisted fracture in SiO2 films using a channel cracking technique

• Published in: Acta materialia Vol. 52; no. 12; pp. 3621 - 3629
• Main Authors: MCELHANEY, Kevin W, QING MA
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Science 12.07.2004
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Metals. Metallurgy; Physics; Rupture; Cracking; Solid state physics; Mechanical properties; Metallurgy; Subcritical crack growth; Thin-film toughness; Silica; Thin film; Crack propagation; Fracture toughness
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2004.04.014

The technique of channel cracking was developed to study moisture-assisted crack growth in SiO2 films, which are used widely in many silicon-based technologies. Films of various residual stresses from tensile to compressive were PECVD deposited, pre-cracked and subjected to an applied uniform tensile stress by bending the silicon substrate using a 4-point beam-bending fixture. The tests were performed in controlled environments: dry ( < 2% RH), ambient (40-60% RH) and wet ( > 90% RH). Crack velocities were varied by changing the applied stress and measured by optically monitoring crack growth in situ. It was observed that under the same moisture conditions, films with higher compressive stresses were tougher than those with higher tensile stresses. The presence of moisture at the crack tip was found to reduce the films' resistance to cracking dramatically. The three principal regions of moisture-assisted cracking established by Weiderhorn in a bulk glass system were also observed.