Following trend towards miniaturization, IC manufacturers are under constant pressure to increase the density of interconnects, with the result that conductors with finer lines and spaces are required. According to the roadmaps of major Original Equipment Manufacturers, Line/Space requirements for copper conductors are set to become increasingly finer, with a target of below 8/8 μm for the near future packaging substrates.
SAP and (a)-MSAP processes involve the plating of the desired circuitry on a thin conductive copper seed layer, followed by the removal of the respective seed layer using a flash/differential etching solution to finalize the circuit formation. These etchants typically contain sulfuric acid or hydrogen peroxide, along with various organic additives. They offer the advantage of uniform and fluid-independent etch attack. However, there are also several drawbacks. For example, these etchants are known to cause undercutting of the conductor tracks (up to several micrometers), affecting the mechanical stability and, consequently, the interfacial integrity of fine line conductors (track width < 8 μm). Furthermore, the solution/process must be run in feed and bleed mode to maintain a stable copper content in the solution and replenish the oxidizer that has been used. This results in the generation of significant quantities of chemical waste, which requires costly treatment.
Alternatively, MKS – MSD has introduced the EcoFlash S300 flash/differential etching process. This new iron sulfate-based differential etchant is designed for <8/8 μm L/S packaging substrates. It features a high etching ratio and is free from undercuts, making it crucial for fine line circuit formation. These attributes distinguish EcoFlash S300 from other conventional flash/differential etching processes.
Features comparison between conventional flash/differential etching process and EcoFlash S300
Additionally, the solid rectangular shape of the conductor traces created by the EcoFlash S300 etching process plays a crucial role in optimizing heat dissipation. This shape increases the surface area for more efficient heat transfer, helping to prevent overheating and ensuring stable operation. Furthermore, the rectangular design allows for consistent and easily controlled current flow, providing reliable electrical performance. Its geometry also makes it ideal for fitting within the compact spaces of modern circuit boards, enabling high-density layouts without compromising on efficiency or performance.
The cross-sectional image of the EcoFlash S300 flash-etched fine conductor trace demonstrates zero undercut and exceptional trace rectangularity
Thanks to its wide operating window, EcoFlash S300 delivers exceptional process stability, effectively minimizing fluctuations and ensuring consistent quality across the entire production cycle. This reliability results in the creation of high-quality circuit patterns, significantly improving production yield compared to conventional flash/differential etching processes. The superior performance of EcoFlash S300 makes it the preferred solution for manufacturing fine L/S 8/8 μm and smaller feature sizes, setting a new standard in precision and efficiency for advanced circuit fabrication. As a result, EcoFlash S300 is the first-choice solution for applications demanding high-precision flash/differential etching.
