A vacuum plasma surface pretreatment for refining seeding of Co in electroless copper plating

摘要

In this work, various vacuum plasma types, generated by either single gaseous sources (N_2 or H_2) or mixed sources (N_2-H_2) are incorporated into an aqueous-solution electrochemical seeding process to pre-treat the surfaces of SiO_2 dielectric layers. Under the optimal plasma atmosphere (monitored by optical emission spectroscopy), the dielectric surfaces can be modified to terminate by hydrophilic bonds, accelerating the adsorption of a crowd of catalytic seeds as small as 3 nm. Such a seeding refinement allows for the growth of a Co-based barrier layer with thickness as thin as 10 nm using electroless plating. Moreover, the capacity of integrating the plasma surface pretreatment with the seeding and electroless-plating process steps to deposit an ultrathin copper-stacked metallization layer in a selective and sequential manner on blanket wafers will be demonstrated by the fabrication of copper-gated and barrier-interposed capacitors. Finally, a tentative work of filling the seeds and the barrier layer into trenches of a patterned wafer was carried out, demonstrating the potential of the reported technique for advanced technology nodes of 60 nm or less.