Thermo-mechanical material characterization of organic polymer films in advanced packages using nanoindentation

In this study we report about thermo-mechanical characterization methods in confined geometries via nanoindentation of polymer packaging materials. An Agilent G200 nanoindenter was lately upgraded with a new 4 watt laser tip and 40 watt laser stage heating option, allowing temperature dependent material analysis with high thermal stability. Thermal gradients from conventional cold indenter tips to heated samples are minimized by using glass fiber technology in order to heat the indenter tip to the same temperature as the tested sample surface. Hence, thermal drifts can be hold very precisely within the resolution limit of nanometer range. By using different indenter geometries (berkovich and sphere) the temperature dependency of two organic photoresist materials is analyzed in dynamic mode and compared to conventional macroscopic characterization methods. We show how the substrate is influencing the measurements and report about how to account for substrate effects. In general, the storage modulus reached comparable results in instrumented indentation and conventional methods, while the loss modulus showed deviations. In the case of the polyimide based dielectric film, the temperature dependent results in storage modulus show a good agreement of micro scale to conventional macro scale characterization methods, while the epoxy based thin film shows results dependent on the indenter tip geometry. It is assumed that the reason for this is the filling of the latter thin film material with rubber particles.