Panel-Based Large-Scale RDL Interposer Fabricated Using 2-μm-Pitch Semi-Additive Process for Chiplet-Based Integration

A panel-based large-scale redistribution-layer (RDL) interposer has been fabricated using a 2-μm-pitch semi-additive process. A key technology in the panel-based processing is dry plasma etching of the Cu-seed/barrier metal layers as it enables precise control of a very narrow trace width (1 μm) while maintaining a high aspect ratio (greater than 3). This controllability was demonstrated by measuring the electrical resistance and electrical isolation of Cu traces. The patterned 2-μm-pitch Cu traces were covered with inorganic dielectrics to increase their reliability. Focusing on the maximum signal transmission distance and energy efficiency of signal transmission, we compared the 2-μm-pitch Cu traces with damascene-based Cu traces by using 3D electromagnetic field simulation. The fabricated large-scale RDL interposer, consisting of five conductive layers, is well suited for achieving high-speed processing in Al, graphics, and other high-performance computing systems.