This study deals with the challenge of warpage in power modules, vital components in the rapidly expanding electric and hybrid-electric vehicle industry. The variations in temperature during manufacturing, resulting in significant warpage changes, contribute to device cracks, delamination, and reduced reliability.
The primary focus is understanding and mitigating the warpage phenomenon in power module substrates. This warpage is induced by thermo-mechanical stresses during the assembly packaging process. The investigation begins by exploring the cause of warpage change by characterizing annealed copper properties and employing 2D finite element model (FEM) analysis. The study identifies plastic strain as the dominant cause of warpage change during process steps. Subsequently, a validated 3D FEM simulation model is developed to replicate practical annealing and sintering processes. Lastly, the project delves into factor analysis to identify critical variables influencing warpage. It underscores that balancing residual copper volume is crucial in warpage reduction. Additive and subtractive manufacturing techniques establish a correlation between the removal of copper volume and warpage reduction.

This project provides comprehensive insights into the manufacturing process of AMB substrate, warpage behavior, and effective strategies for reduction, constructing a solid foundation for future manufacturing and design.

Many semiconductor sensors, particularly MEMS sensors such as inertial, temperature, pressure, and resonance sensors need a vacuum environment for optimal performance and sensitivity in addition to the improvement in their long-term reliability. With the rise of heterogeneous integration with the MEMS and ICs being integrated together, process compatibility becomes a very big issue. Cu is a desirable bonding and sealing material for low-temperature vacuum packaging of next-generation microsystems, as it is compatible with modern CMOS circuits and 3-D IC fabrication. Cu thermocompression bonding has been reported to achieve vacuum sealing at low temperatures, but these approaches need extremely flat and clean Cu surfaces or additional capping layers, and the overall bonding areas are still rather large.
To mitigate this, the use of copper nanoparticles as the sealing material has been proposed. In this study, the first successful demonstration of die and multi-die level hermetic sealing has been demonstrated using Copper nanoparticle paste as the sealing material for sealing ring widths as small as 8$\mu$ at a minimum temperature and pressure levels of 300$^\circ$C and 10 MPa respectively with average encapsulated pressure of 54.18 mbar. Moreover, the leak rate evaluation was conducted which revealed no discernable leakage over a period of 48 days. Finally, the bond shear test and a subsequent failure analysis revealed high densification of the Copper nanoparticles at the bond interface.

Metal oxide nanoparticle gas sensors showpromise due to their high sensitivity towards a wide range of gases, low costs, and low complexity. Particle sizes at nanometers offer a high surface-to-volume ratio which provides more areas on the surface where reactions can occur. This work presents the application of spark ablated nanoparticles on chemiresistors and chemFETs, and does a study on whether spark ablated nanoparticles are a viable alternative to nanoparticles generated using other methods. The focus in this thesis is on pure metal oxide nanoparticles without any addition of dopants or decorations. Devices are fabricated with different interdigitated electrode dimensions. The effect of electrode width and gap size on the gas response is studied by comparing the sensing performance of the devices. In this work, a very high sensitivity of 1300% is achieved towards 35% relative humidity using a 1x1 mm device with SnO2 nanoparticles. Towards 20 ppm of ethanol, sensitivities of 39% and 67% are achieved using 1x1 mm and 4x1 mm devices with SnO2 nanoparticles respectively, which implies that spark ablated nanoparticles could be a viable alternative to particles generated using other methods. The full recovery time after gas exposure seems to be very long and takes around an hour for some devices at 200 °C. Possible solutions for this are setting a higher temperature (not possible with the used setup), or reducing the particle size (∼20 nm in this study). The electrode finger widths and gap sizes are varied between 2-15 μm for each device. However, no correlation is found between electrode geometry and gas response within this range, suggesting that differences in gas response between devices likely stem from nanoparticle layer quality differences.