Buckle induced delamination techniques to measure the adhesion of metal dielectric interfaces

Abstract

Adhesion of thin metal films on dielectric substrates is one of the most important properties in microelectronic devices due to the fact that interface adhesion determines the device lifetime and reliability. In order to improve the lifetime of these devices, substrate treatments and adhesion layers are often utilized, making a quantitative assessment of adhesion of the utmost importance. A key example of a metal film common in many microelectronic devices is Tungsten-Titanium (WTi), which is used as a diffusion barrier and an adhesion layer. Several testing methods and mechanics-based models have been developed over the last decades to quantitatively evaluate interface adhesion of thin metal films on rigid substrates. For thin films on rigid substrates (i.e. dielectrics or silicon) the most viable methods are mechanical techniques such as nanoindentation and scratch induced delamination because of the simplicity of the test setup and sample preparation. During indentation or scratching, stresses are induced into the film system which can cause interface separation in the form of buckles. By measuring the dimensions of the buckle and employing the appropriate model, the interfacial adhesion energy can be quantitatively determined. These techniques were utilized to induce interface delamination of a WTi film on different borophosphosilicate glass (BPSG) substrates. The comparison of the results from the different techniques will provide more insight into the techniques applicability and help to better characterize the adhesion of similar film systems.