(633d) Wet-Chemical And Plasma Treatments To Enhance Adhesion Between Electroless Copper And Dielectric Materials

Electroless copper plating on current and future dielectric materials is a key to the development of semiconductor devices that require ever smaller features. Catalyst adsorption and adhesion between the dielectric material and the electroless copper layer must be improved in order to enable electroless copper plating. Current technology relies on high surface roughness and the creation of large pore structures on the polymer surface to enable adhesion through mechanical interlocking. As feature sizes continue to shrink, however, these roughness levels become unfeasible as they impair feature performance. Future dielectric materials must be treated in a manner which produces smoother surfaces while maintaining adequate adhesion. A key to improving adhesion while minimizing roughness is to combine mechanical anchoring with increased chemical bonding at the surface. This study looks at the role of both mechanical anchoring and chemical bonding in the adhesion of electroless copper to dielectric materials. In particular wet-chemical treatments are used to enhance adhesion through mechanical anchoring and plasma treatments are utilized for chemical bonding improvements. A final treatment approach combines wet-chemical and plasma treatments in order to achieve the benefits of both chemical bonding and mechanical anchoring. The surfaces resulting from these treatments have been characterized with atomic force microscopy (AFM) for morphological changes and X-ray photoelectron spectroscopy (XPS) for the chemical state of the surface. Finally 900 peel tests were used to quantify the adhesion between electroless copper and the dielectric material. In this manner the chemical and mechanical bonding contributions can be quantified and correlated with changes in adhesion. The final result is a set of treatment conditions that produce smooth surfaces while maintaining adhesion through a combination of chemical bonding and mechanical anchoring.