Adhesion strength testing using a depth-sensing indentation technique

Abstract

A nanoindentation apparatus is used to measure adhesion strength of a hard, thin film to a soft substrate. A variably increasing load is applied to the indenter tip. The indenter tip penetrates into the thin film at a first penetration rate and causes the thin film to sink into the substrate thus causing a tensile stress at the film substrate interface. At a critical value of the applied load, the stress at the interface exceeds the delamination value, and the thin film partially delaminates from the substrate. This causes the indenter tip to sink into the softer substrate at a sudden second, higher penetration rate. A sensor detects the applied load and the indenter tip penetration depth at this point. A computer flags the critical value of the applied load that corresponds to the increased penetration depth rate at the point of delamination of the film. The computer then calculates the critical stress required for delamination and the adhesion strength between the film and the substrate from the critical value of the applied load. The depth sensing indentation technique measurement may be carried out on a thin film integrated test element so as not to damage the rest of the thin film. The method allows non-destructive in-situ adhesion strength measurements for thin films and microelectronic devices.