Thermal and thermomechanical characterization and diagnostics of electronic packaging and interconnect systems

The development of integrated circuits (ICs) faces important thermal and thermomechanical challenges, at both the packaging and interconnect levels. Increasing integration of ICs leads to increasing heat generation. This poses thermal challenges at the packaging level, and motivates advanced thermal management solutions for ICs. Increasing heat generation also poses thermomechanical challenges at the packaging level due to thermomechanical deformations induced by materials with different thermal and thermomechanical properties. Moreover, increasing heat generation poses thermal challenges at the interconnect level, especially to Cu/low-k interconnect systems due to the poor thermophysical properties of low-k dielectrics. The integration of low-k dielectrics into interconnect systems also poses thermomechanical challenges at the interconnect level due to the poor thermomechanical properties of low-k dielectrics.; This dissertation focuses on the characterizations and diagnostics of thermal and thermomechanical phenomena in electronic packaging and interconnect systems. (1) A review chapter describes novel approaches for reducing spreader-ambient thermal resistance through compact closed-loop forced-convective cooling systems. Three types of micro heat exchangers, available micro or meso scale pumping technologies, as well as system design and integration concerns are discussed. (2) A transient model based on classical theories for lubrication and surface wettability provides a simple relationship for junction-spreader thermal resistance. Predictions from this model agree reasonably well with various experimental results on the pressure dependence, the thickness dependence, and the filler volume fraction dependence of the junction-spread thermal resistance. (3) A steady state, IC-compatible technique measures thermal conductivities of four low-k dielectric thin films. Temperature fields in Cu interconnect structures are predicted using the measured thermal conductivity data and finite element analysis (FEA), and are verified experimentally using both infrared (IR) thermometry and electrical thermometry. Two damage-site-identification techniques for electromigration tests on via-chain structures are demonstrated: In-situ IR thermal diagnostics and voltage potential contrast electron microscopy. Temporal and spatial damage dynamics during electromigration is visualized by in-situ IR thermal diagnostics. (4) Two thermomechanical diagnostic techniques are developed: Phase-shifting speckle interferometry (PSSI), and digital image/speckle correlation (DISC). These techniques are then applied to thermomechanical diagnostics of various electronic packaging structures.