Electroless Copper Plating Stack for Tungsten Adhesion

The patent divides the plating process into multiple stages with intermediate layers. Instead of directly plating Cu on W, it introduces Pd seeding clusters as an intermediate layer, and uses Cu clusters as further intermediates. This segmentation creates gradual transitions between materials with different properties, ensuring strong adhesion at each interface while maintaining overall process feasibility.

The patent introduces intermediary materials (Pd seeding clusters and Cu clusters) between Tungsten and the final Cu layer. These intermediaries serve as mediators that facilitate bonding between incompatible materials. The Pd clusters act as nucleation sites that enable subsequent Cu deposition, creating strong interfacial adhesion through controlled cluster formation and growth.

The patent replaces the harmful formaldehyde stabilizer with alternative stabilizing agents that eliminate health and safety hazards while maintaining plating effectiveness. This substitution converts a harmful process into a safe one, removing fuming and toxicity issues without sacrificing the ability to produce uniform, adherent Cu layers on complex substrates.

The patent modifies the chemical parameters of the plating solution by substituting formaldehyde with alternative stabilizers. This parameter change maintains the essential function of stabilization (preventing premature Cu precipitation) while eliminating the harmful properties of formaldehyde, achieving both safety and effectiveness requirements.

The patent segments the deposition process into controlled stages: Pd cluster formation, Cu cluster nucleation on Pd clusters, and final Cu layer growth. Each stage occurs under optimized conditions that ensure both uniform distribution and strong adhesion. The cluster-based approach naturally promotes even coverage while the intermediate layers ensure robust bonding at each interface.

The patent uses Pd seeding clusters and Cu clusters as intermediary layers that simultaneously provide adhesion and promote uniform deposition. These intermediaries create a gradient structure that facilitates both strong bonding to the substrate and uniform growth of the final Cu layer, resolving the contradiction between adhesion strength and deposition uniformity.