Three-dimensional microfabrication technologies for electronic and lab-on-chip applications

The density of heterogeneous three-dimensional integrated circuits (3D-ICs) is significantly limited by through-silicon-via (TSV) density and cooling challenges. To enable fine-grain 3D-ICs, high aspect-ratio sub-micron diameter (~920 nm) TSV technology is demonstrated. To address cooling challenges and pronounced thermal wall limits in 3D-IC technology, a monolithic microfluidic cooling strategy is explored. Specifically, a thermal testbed with non-uniform power map and integrated microfluidics at the back side of the silicon die is microfabricated. While the proposed silicon-based microfluidic cooling is shown to provide thermal benefits, the silicon Bosch process introduces a number of challenges on a fully processed CMOS wafer, in particular introducing crystalline defects, reducing silicon volume and thus increasing wafer warpage. As an alternative, a novel metal additive manufacturing technology is developed as a key enabler for microfabricating a metallic microfluidic heatsink at the die-level and wafer-level. As a result, we demonstrate additively manufactured 200 µm diameter copper (Cu) pillars as the key heat dissipating elements for monolithically integrated microfluidic heatsinks. Lastly, it is discovered that there is a wide need for the scallop-free sub-micron deep silicon etching process that was developed for the high-density 3D-IC project. By leveraging this enabling process, a lab-on-chip device is microfabricated to study, for the first time, bio-physical interactions of red-blood-cells (RBCs) with their surrounding environment in vitro.Ph.D