Electrostatic adhesion testing of metallizations on silicon substrates
Yang, Haining Sam
Brotzen, Franz R.
Doctor of Philosophy thesis
A novel technique is developed to measure quantitatively the adhesion strength of metallizations deposited on substrates such as silicon. Electrostatic adhesion testing employs electrostatic forces to generate delaminating stresses in thin metallic films. The interfacial adhesion strength is readily calculated from the electrode geometry and the applied electrostatic field at failure. Unlike other adhesion tests, this technique does not require any mechanical contact and is virtually independent of the plastic deformation of the film. Furthermore. this test provides direct strength measurements as opposed to work or energy of adhesion measurements obtained by the common peel-test. The adhesion strengths of several metallizations (Cu, Al, Al-Cu alloy, and TiN) are characterized using this electrostatic technique. The distribution of stress-at-failure data follows Weibull statistics. Field emission scanning electron microscopy reveals that films are delaminated in a micro-blister-type mode. Annealing of metallizations causes reactions and changes flaw distributions. The presence of brittle compounds near the interface may create easy fracture paths and can act as stress concentrators to initiate and propagate the fracture. These stressed areas may lead to localized adhesion failure under applied stress. It is shown that electrostatic adhesion testing is effective in providing quantitative values for the adhesion strengths and failure probabilities of thin-film metallizations.
Engineering, Materials Science