Implanted argon atoms as sensing probes of residual stress in ultrathin films

A technique for evaluating residual stresses in ultrathin films is presented and its effectiveness is demonstrated in light of residual stress measurements obtained for amorphous carbon (a-C) films of thickness 10-70 nm deposited on Si(100) substrates by radio-frequency sputtering. In this technique, small amounts of Ar atoms implanted within the near-surface region of the films are used as stress-sensing probes. The method is based on the effect of the film residual stress on the binding energy shift of the 2p electrons of implanted (or incorporated) Ar atoms determined from x-ray photoelectron spectroscopy. The basic requirements of this technique are discussed and its potential to determine residual stresses in ultrathin films is illustrated in light of comparisons with results obtained with a conventional stress measurement technique and annealing experiments performed with a-C films. The residual stress in the as-deposited a-C films, sensed by the incorporated Ar atoms, is confirmed by stress measurements based on the change of the sample curvature. In addition, the residual stress in a-C films leading to debonding after annealing, predicted by the present method, is shown to be in good agreement with that calculated from a blistering model for thin films under equibiaxial compression. (C) 2000 American Institute of Physics. [S0003-6951(00)00722-1].