Controllable Deposition of Polyimide Insulation Layer by an Engineered Stepped Pre-curing Method in Double-sided TSV Processes

Through-silicon-via (TSV) technology has shown great advantages in the advanced electronic packaging area. In this work, we deeply investigate the feasibility of a novel double-sided polyimide (PI) liner fabrication technology, which is beneficial to the cost-effective and high-reliability manufacture of TSVs. We experimentally demonstrate that the temperature control during the pre-curing step in the formation of the backside PI insulation layer has a significant effect on the morphology of the deposited PI layer. Therefore, an engineered stepped pre-curing method is proposed to enhance the process yield of the back-side PI deposition, and further guarantee the formation of an intact PI liner alongside the TSV sidewalls and the double sides of the substrate. The stepped pre-curing method consists of three stages, including low-temperature solvent evaporation and initial shaping, mid-temperature film thinning and breakage, and high-temperature protrusion shaping. Results show that the uniformity of the exposed via openings in the back-side PI layer is excellent, and the formed PI liner exhibits a good integrity. This optimized double-sided PI liner fabrication technology facilitates the subsequent processes based on through holes, thus providing a low-cost and reliable approach to the manufacture of TSVs for a better integration of heterogeneous electronic devices.