The Effects Of Moisture On Thin Film Delamination And Adhesion

Significant drops in adhesion have been measured for copper and diamond like carbon (DLC) films with the introduction of water at the film/substrate interface. A 1 thick tungsten superlayer with high compressive residual stress was deposited on the films of interest to help induce interfacial debonding by indentation. Modifications were made to the superlayer indentation technique to introduce water at the interface while performing indents. Film adhesion dropped by a factor of 10 to 20 for the copper films and 50 to 60 for the DLC films. The reduction in adhesion is believed to be caused by a combination of lowering surface energy and a chemical reaction at the crack tip. When the film compressive residual stress is at least 4 times the critical buckling stress of a debonded film, telephone cord delaminations morphology can be observed. Delamination propagation has been induced in the past by applying a mechanical force to the film and similar results have been observed with the introduction of water. Crack propagation rates of 2 to 3 microns per second were measured for the DLC films with the introduction of water at the film/substrate interface. Telephone cord delaminations show potential for future use as microchannels in microfluidic devices and have shown excellent stability when manipulated with a microprobe to control fluid transport