Determining interfacial properties of submicron low-k films on Si substrate by using wedge indentation technique

This article presents studies on using a wedge indentation technique to determine interfacial adhesion properties of low-k dielectric films, namely, methyl-silsesquioxane (MSQ) and black diamond (BD (TM))films, both on a Si substrate. Interfacial crack initiation and propagation processes in the MSQ/Si system are studied by using focused-ion-beam sectioning of the indentation impressions created by wedge tips with 90 degrees and 120 degrees of inclusion angles, respectively. Furthermore, the indentation induced stress is found to be proportional to the ratio of the indentation volume and the interface delamination crack volume for both plane strain and nonplane strain cases. With this analysis, the interface toughness of the MSQ/Si and BD/Si system, in terms of the strain energy release rate, is determined. The interface toughness for the MSQ/Si system is found to be a value of 1.89 +/- 0.28 J/m(2) for the 90 degrees wedge tip indentation and 1.92 +/- 0.08 J/m(2) for the 120 degrees wedge tip indentation. In addition, using the 120 degrees wedge tip, the interface toughnesses of the BD films on the Si substrate with 200 and 500 nm thicknesses are found to be the values of 6.62 +/- 1.52 and 6.35 +/- 2.27 J/m(2), respectively. (c) 2007 American Institute of Physics.