L/S ≤ 5/5μm Line Embedded Organic Substrate Manufacturing for 2.1D/2.5D SiP Application

摘要

The requirement for IC packages with higher density interconnection with fine line feature has increased significantly recently. Current organic substrates are limited to line/space 8/8μm for Semi-additive Process (SAP), and it will cause yield loss from adhesion issue of line/space less than 5/5μm. But the impact of bad adhesion of fine line is very small in laser embedded (LE) substrate because of its embedded structure. There are several advantages of LE such as the capacity of stereo copper features and better electric performance with lower variation of trench width/depth. It can form fine pitch trench line/space even less than 3/3μm. It also can provide better design flexibility for its pad-less features and better reliability than SAP process. In this paper, we will discuss the key of the processes and demonstrate the fabrication of fine line substrate of 3/3μm line/space by fine tuning line embedded technology. Line embedded trace was made by laser direct ablation (LDA) on organic build-up dielectric material with fine filler size. Laser ablation process capability shows excellent trench depth and shape control. In order to get better copper thickness uniformity, novel uniformity copper plating technology on via, pad and trench has developed. Low cost and uniformity copper reduction process has also been evaluated and developed.