Novel Adhesion Test for Environmentally Assisted Fracture in Thin Films

摘要

Thin films, used in various applications and devices, must strongly adhere to their substrates. Due to various processing and storage environments that devices can be exposed to, water may be introduced into the system. If residual stresses are present in a thin film, delamination propagation can be driven by water without the assistance of an externally applied mechanical force. It is extremely important to measure coating adhesion quantitatively, taking into account environmental effects. This paper describes general mechanics approach to moisture effects on delamination of stressed thin films, with diamond like carbon films (DLC) used in the hard drive industry as an example. DLC film adhesion has been measured to drop by a factor of 50 to a 100 using the modified superlayer indentation test. Crack propagation rates in DLC films have been recorded up to a few microns per second. The reduction of DLC film adhesion and delamination propagation is attributed to water lowering the surface energy at the crack tip.