Development of a Plasma Etching Process of Copper for the Microfabrication of High-Density Interconnects in Advanced Packaging

Current microfabrication approaches face many challenges when scaling down to form copper lines of less than 2 μm line/space width on organic substrates, resulting in issues such as lateral etching and undercut. In this work, a one-step Ar/H
2
/Cl
2
plasma etching process has been developed, allowing to replace wet etching of the seed layer in the semi-additive process (SAP) approach. By optimizing the etch process, we demonstrate the fabrication of high-density copper-based RDL with an L/S of ∼1.65 μm with a Cu etch rate of 150 nm/min on a packaging substrate.