Sub-Micron Patterning & High-Aspect-Ratio Structures in Advanced Substrates with Dry Etching and Liquid Metal Ink Metallization

The growing demand for Panel Level Packaging to meet the needs of High-Performance Computing (HPC), Artificial Intelligence (AI) and advanced chiplet architecture requires a scalable solution for ultra-high-density and high-signal integrity interconnects. Ajinomoto Build-up Film (ABF) is a proven dielectric material in advanced packaging due to its low dielectric loss and fine-pitch compatibilities, enabling reliable ultra-dense pattern formation and high-performance device integration. While laser via formation is a conventional approach for ABF processing, its sequential nature makes it slow and challenging to scale to a cost-effective panel-level process. In addition, it suffers from thermal damage effects and debris accumulation, making it challenging to achieve ultra-small features. These limitations create bottlenecks in high-density interconnect fabrication, impacting throughput, cost, and signal integrity. By contrast, dry etching offers a more controlled and precise batch-process alternative, eliminating the need for chemical desmear, and enabling better feature profile definition, significantly higher aspect ratios, and minimal residue and thermal damage. This study explores the use of different hard mask materials for ABF dry etching and examines the impact of etching parameters on feature profile and selectivity. While photoresist masks struggle to achieve small feature diameters and high aspect ratios, the optimized dry etching process with metal hard masks in our study successfully achieved sub-1μm features with 10:1 aspect ratios. Additionally, Laser Direct Imaging (LDI) was utilized to create precise patterning, demonstrating a flexible and scalable method for high-density pattern fabrication in advanced panel-level packaging. Following structure formation, the application of a novel Liquid Metal Ink deposition process was evaluated, demonstrating a scalable, reliable, and cost-effective method of fine-resolution copper metallization in advanced Panel Level Packaging applications. LMI compatibility with Epoxy Mold Compounds (EMC) was also evaluated. Fine-line patterning is demonstrated on EMC and RDL materials to assess the feasibility of the Liquid Metal Ink approach for high-density interconnects in Fan-Out Wafer Level Packaging (FOWLP) applications.